Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Hoi, In OmegaWiki we made the choice that any "defined meaning" can be used as a property. This makes OmegaWiki more like a Wiki than Wikidata were properties have to be created by fiat. What was found is that people tend to not abuse this and there is a limited set that is used as "properties".
When you do not insist on the artificial limits implicit in properties, there will be one victim; it is the structure of the ontology. However when you analyse things, such a structure still exists it is just no longer formal. In a way it is similar to the early insistence on using the "GND types", they did not fit but thankfully we kept the "GND identifier" in this way we left the structure of GND where it belonged; in GND itself. They can map to their hearts content our content using their structure.
One final thought, when we have enough data, we can manipulate it. Because of a lack of data we are still left with many GND types.
PS there is nothing wrong in leaving things as they are.. It works more or less. Thanks, Geard
On 28 May 2014 09:25, David Cuenca dacuetu@gmail.com wrote:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
Key differences between Properties and Items:
* Properties have a data type, items don't. * Items have sitelinks, Properties don't. * Items have Statements, Properties will support Claims (without sources).
The software needs these constraints/guarantees to be able to take shortcuts, provide specialized UI and API functionality, etc.
Yes, it would be possible to use items as properties instead of having a separate entity type. But they are structurally and functionally different, so it makes sense to have a strict separate. This makes a lot of things easier, e.g.:
* setting different permissions for properties * mapping to rdf vocabularies
More fundamentally, they are semantically different: an item describes a concept in "the real world", while a property is a structural component used for such a description.
Yes, properies are simmilar to data items, and in some cases, there may be an item representing the same concept that is represented by a property entity. I don't see why that is a problem, while I can see a lot of confusion arising from mixing them.
-- daniel
Am 28.05.2014 09:25, schrieb David Cuenca:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
On 28/05/14 10:37, Daniel Kinzler wrote:
Key differences between Properties and Items:
- Properties have a data type, items don't.
- Items have sitelinks, Properties don't.
- Items have Statements, Properties will support Claims (without sources).
The software needs these constraints/guarantees to be able to take shortcuts, provide specialized UI and API functionality, etc.
Yes, it would be possible to use items as properties instead of having a separate entity type. But they are structurally and functionally different, so it makes sense to have a strict separate. This makes a lot of things easier, e.g.:
- setting different permissions for properties
- mapping to rdf vocabularies
This one point requires a tiny remark: there is no problem in OWL or RDF to use the same URI as a property, an individual, and a class in different contexts. The only thing that OWL (DL) forbids is to use one property for literal values (like string) and for object values (like other items), but this would not occur in our case anyway since we have clearly defined types. I completely agree with all the rest :-)
Cheers,
Markus
More fundamentally, they are semantically different: an item describes a concept in "the real world", while a property is a structural component used for such a description.
Yes, properies are simmilar to data items, and in some cases, there may be an item representing the same concept that is represented by a property entity. I don't see why that is a problem, while I can see a lot of confusion arising from mixing them.
-- daniel
Am 28.05.2014 09:25, schrieb David Cuenca:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
Am 28.05.2014 11:44, schrieb Markus Krötzsch:
This one point requires a tiny remark: there is no problem in OWL or RDF to use the same URI as a property, an individual, and a class in different contexts. The only thing that OWL (DL) forbids is to use one property for literal values (like string) and for object values (like other items), but this would not occur in our case anyway since we have clearly defined types. I completely agree with all the rest :-)
Yea, I didn't mean to say that there is an issue with representing this in RDF, but with mapping to RDF vocabularies. Having a relatively limited and stable set of properties to map makes that a lot easier.
-- daniel
On Wed, May 28, 2014 at 10:37 AM, Daniel Kinzler < daniel.kinzler@wikimedia.de> wrote:
More fundamentally, they are semantically different: an item describes a concept in "the real world", while a property is a structural component used for such a description.
As I perceive it, a property is a normal item (concept) imbued with the option to use it as predicate and allow it to use different datatypes. There is no property that cannot be expressed as an item, even properties that represent an identifier, they also could be said that they are a concept in the real world. I understand that from the software side you need to make a difference between "basic concepts" (items) and "concepts that can be used as predicates" (properties). From the community side we also need to scrutinize and "rinse" the concepts that hide behind the words before using them as predicates, but sometimes it is good to stop and consider what are we really doing.
Yes, properies are simmilar to data items, and in some cases, there may be
an item representing the same concept that is represented by a property entity.
I haven't found yet a property that couldn't be expressed as an item.
I don't see why that is a problem, while I can see a lot of confusion arising from mixing them.
It is not a problem now but I considered interesting to analyze what is the substance of the distinction. If properties and concepts are separate in the end we will be reproducing their ontological structure when organizing them. So then it might not make sense to use "subproperty of" to organize properties, but just "corresponds to item".
Gerard, thanks for bringing the example of OmegaWiki, it is interesting that two independent communities came to the same thoughts without any contact between them :)
Cheers, Micru
One other issue to bear in mind: it's *simple* to have properties as a separate thing. I have been following this discussion with some interest but... well, I don't think I'm particularly stupid, but most of it is completely above my head.
Saying "here are items, here are a set of properties you can define relating to them, here's some notes on how to use properties" is going to get a lot more people able to contribute than if they need to start understanding theoretical aspects of semantic relationships...
;-)
Andrew.
On 28 May 2014 09:37, Daniel Kinzler daniel.kinzler@wikimedia.de wrote:
Key differences between Properties and Items:
- Properties have a data type, items don't.
- Items have sitelinks, Properties don't.
- Items have Statements, Properties will support Claims (without sources).
The software needs these constraints/guarantees to be able to take shortcuts, provide specialized UI and API functionality, etc.
Yes, it would be possible to use items as properties instead of having a separate entity type. But they are structurally and functionally different, so it makes sense to have a strict separate. This makes a lot of things easier, e.g.:
- setting different permissions for properties
- mapping to rdf vocabularies
More fundamentally, they are semantically different: an item describes a concept in "the real world", while a property is a structural component used for such a description.
Yes, properies are simmilar to data items, and in some cases, there may be an item representing the same concept that is represented by a property entity. I don't see why that is a problem, while I can see a lot of confusion arising from mixing them.
-- daniel
Am 28.05.2014 09:25, schrieb David Cuenca:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
-- Daniel Kinzler Senior Software Developer
Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
Héhé, the Wikidata game suggest it may be a little bit too complicated and better abstracted away by a three button game for mass contribution :)
2014-05-29 21:04 GMT+02:00 Andrew Gray andrew.gray@dunelm.org.uk:
One other issue to bear in mind: it's *simple* to have properties as a separate thing. I have been following this discussion with some interest but... well, I don't think I'm particularly stupid, but most of it is completely above my head.
Saying "here are items, here are a set of properties you can define relating to them, here's some notes on how to use properties" is going to get a lot more people able to contribute than if they need to start understanding theoretical aspects of semantic relationships...
;-)
Andrew.
On 28 May 2014 09:37, Daniel Kinzler daniel.kinzler@wikimedia.de wrote:
Key differences between Properties and Items:
- Properties have a data type, items don't.
- Items have sitelinks, Properties don't.
- Items have Statements, Properties will support Claims (without
sources).
The software needs these constraints/guarantees to be able to take
shortcuts,
provide specialized UI and API functionality, etc.
Yes, it would be possible to use items as properties instead of having a separate entity type. But they are structurally and functionally
different, so
it makes sense to have a strict separate. This makes a lot of things
easier, e.g.:
- setting different permissions for properties
- mapping to rdf vocabularies
More fundamentally, they are semantically different: an item describes a
concept
in "the real world", while a property is a structural component used for
such a
description.
Yes, properies are simmilar to data items, and in some cases, there may
be an
item representing the same concept that is represented by a property
entity. I
don't see why that is a problem, while I can see a lot of confusion
arising from
mixing them.
-- daniel
Am 28.05.2014 09:25, schrieb David Cuenca:
Since the very beginning I have kept myself busy with properties,
thinking about
which ones fit, which ones are missing to better describe reality, how
integrate
into the ones that we have. The thing is that the more I work with
them, the
less difference I see with normal items.... and if soon there will be
statements
allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it
might make
sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we
adding
unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
-- Daniel Kinzler Senior Software Developer
Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
--
- Andrew Gray andrew.gray@dunelm.org.uk
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
Let me also chime in and just say that I have never even touched that "fuzzy control" button on my washing machine.
But seriously, I agree with Andrew that some examples are needed. As a member of the IEG committee I am aware how diffiicult it is to explain to outsiders how to go about applying for new properties to be added to WikIData (in the case I am thinking of, it was for properties having to do with Economics-related concepts).
Personally I have found it helpful to look at the items for Berlin (one of the earliest and best defined cities), and the Mona Lisa (one of the earliest and best defined works of art) to become inspired about properties and how they relate to items. It will be a challenge going forward to help people both apply for and judge applications for properties. And yes, Wikimedia categories are starting to look a lot less messy to me...
2014-05-29 21:14 GMT+02:00, Thomas Douillard thomas.douillard@gmail.com:
Héhé, the Wikidata game suggest it may be a little bit too complicated and better abstracted away by a three button game for mass contribution :)
2014-05-29 21:04 GMT+02:00 Andrew Gray andrew.gray@dunelm.org.uk:
One other issue to bear in mind: it's *simple* to have properties as a separate thing. I have been following this discussion with some interest but... well, I don't think I'm particularly stupid, but most of it is completely above my head.
Saying "here are items, here are a set of properties you can define relating to them, here's some notes on how to use properties" is going to get a lot more people able to contribute than if they need to start understanding theoretical aspects of semantic relationships...
;-)
Andrew.
On 28 May 2014 09:37, Daniel Kinzler daniel.kinzler@wikimedia.de wrote:
Key differences between Properties and Items:
- Properties have a data type, items don't.
- Items have sitelinks, Properties don't.
- Items have Statements, Properties will support Claims (without
sources).
The software needs these constraints/guarantees to be able to take
shortcuts,
provide specialized UI and API functionality, etc.
Yes, it would be possible to use items as properties instead of having a separate entity type. But they are structurally and functionally
different, so
it makes sense to have a strict separate. This makes a lot of things
easier, e.g.:
- setting different permissions for properties
- mapping to rdf vocabularies
More fundamentally, they are semantically different: an item describes a
concept
in "the real world", while a property is a structural component used for
such a
description.
Yes, properies are simmilar to data items, and in some cases, there may
be an
item representing the same concept that is represented by a property
entity. I
don't see why that is a problem, while I can see a lot of confusion
arising from
mixing them.
-- daniel
Am 28.05.2014 09:25, schrieb David Cuenca:
Since the very beginning I have kept myself busy with properties,
thinking about
which ones fit, which ones are missing to better describe reality, how
integrate
into the ones that we have. The thing is that the more I work with
them, the
less difference I see with normal items.... and if soon there will be
statements
allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it
might make
sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we
adding
unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
-- Daniel Kinzler Senior Software Developer
Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
--
- Andrew Gray andrew.gray@dunelm.org.uk
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
On 29/05/14 21:04, Andrew Gray wrote:
One other issue to bear in mind: it's *simple* to have properties as a separate thing. I have been following this discussion with some interest but... well, I don't think I'm particularly stupid, but most of it is completely above my head.
Saying "here are items, here are a set of properties you can define relating to them, here's some notes on how to use properties" is going to get a lot more people able to contribute than if they need to start understanding theoretical aspects of semantic relationships...
Good point. The thread has really gone off in a rather philosophical direction :-) As Jane said, examples (of places where a property should be used *and* of places where it should not be used) are definitely much more useful to help our editors on the ground. I usually use items I know as role models or have a look for suitable showcase items.
Markus
On 28 May 2014 09:37, Daniel Kinzler daniel.kinzler@wikimedia.de wrote:
Key differences between Properties and Items:
- Properties have a data type, items don't.
- Items have sitelinks, Properties don't.
- Items have Statements, Properties will support Claims (without sources).
The software needs these constraints/guarantees to be able to take shortcuts, provide specialized UI and API functionality, etc.
Yes, it would be possible to use items as properties instead of having a separate entity type. But they are structurally and functionally different, so it makes sense to have a strict separate. This makes a lot of things easier, e.g.:
- setting different permissions for properties
- mapping to rdf vocabularies
More fundamentally, they are semantically different: an item describes a concept in "the real world", while a property is a structural component used for such a description.
Yes, properies are simmilar to data items, and in some cases, there may be an item representing the same concept that is represented by a property entity. I don't see why that is a problem, while I can see a lot of confusion arising from mixing them.
-- daniel
Am 28.05.2014 09:25, schrieb David Cuenca:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
-- Daniel Kinzler Senior Software Developer
Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
On Fri, May 30, 2014 at 9:18 AM, Markus Krötzsch markus@semantic-mediawiki.org wrote:
On 29/05/14 21:04, Andrew Gray wrote:
One other issue to bear in mind: it's *simple* to have properties as a separate thing. I have been following this discussion with some interest but... well, I don't think I'm particularly stupid, but most of it is completely above my head.
Saying "here are items, here are a set of properties you can define relating to them, here's some notes on how to use properties" is going to get a lot more people able to contribute than if they need to start understanding theoretical aspects of semantic relationships...
Good point. The thread has really gone off in a rather philosophical direction :-) As Jane said, examples (of places where a property should be used *and* of places where it should not be used) are definitely much more useful to help our editors on the ground. I usually use items I know as role models or have a look for suitable showcase items.
Soon the entity suggester will help you here by simply suggesting a list of properties likely missing in the item. Currently blocked on some final code-review at the Foundation. /me goes and pokes again.
Cheers Lydia
Do we have an easy way of highlighting a gallery of good examples or even a plain wikipage of topical guidance? Would be very useful if we could say 'here's a politician, here's a French city, etc'
Andrew. On 30 May 2014 08:19, "Markus Krötzsch" markus@semantic-mediawiki.org wrote:
On 29/05/14 21:04, Andrew Gray wrote:
One other issue to bear in mind: it's *simple* to have properties as a separate thing. I have been following this discussion with some interest but... well, I don't think I'm particularly stupid, but most of it is completely above my head.
Saying "here are items, here are a set of properties you can define relating to them, here's some notes on how to use properties" is going to get a lot more people able to contribute than if they need to start understanding theoretical aspects of semantic relationships...
Good point. The thread has really gone off in a rather philosophical direction :-) As Jane said, examples (of places where a property should be used *and* of places where it should not be used) are definitely much more useful to help our editors on the ground. I usually use items I know as role models or have a look for suitable showcase items.
Markus
On 28 May 2014 09:37, Daniel Kinzler daniel.kinzler@wikimedia.de wrote:
Key differences between Properties and Items:
- Properties have a data type, items don't.
- Items have sitelinks, Properties don't.
- Items have Statements, Properties will support Claims (without
sources).
The software needs these constraints/guarantees to be able to take shortcuts, provide specialized UI and API functionality, etc.
Yes, it would be possible to use items as properties instead of having a separate entity type. But they are structurally and functionally different, so it makes sense to have a strict separate. This makes a lot of things easier, e.g.:
- setting different permissions for properties
- mapping to rdf vocabularies
More fundamentally, they are semantically different: an item describes a concept in "the real world", while a property is a structural component used for such a description.
Yes, properies are simmilar to data items, and in some cases, there may be an item representing the same concept that is represented by a property entity. I don't see why that is a problem, while I can see a lot of confusion arising from mixing them.
-- daniel
Am 28.05.2014 09:25, schrieb David Cuenca:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
-- Daniel Kinzler Senior Software Developer
Wikimedia Deutschland Gesellschaft zur Förderung Freien Wissens e.V.
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
On Fri, May 30, 2014 at 10:06 AM, Andrew Gray andrew.gray@dunelm.org.uk wrote:
Do we have an easy way of highlighting a gallery of good examples or even a plain wikipage of topical guidance? Would be very useful if we could say 'here's a politician, here's a French city, etc'
https://www.wikidata.org/wiki/Wikidata:Showcase_items :)
On Thu, May 29, 2014 at 9:04 PM, Andrew Gray andrew.gray@dunelm.org.uk wrote:
One other issue to bear in mind: it's *simple* to have properties as a separate thing. I have been following this discussion with some interest but... well, I don't think I'm particularly stupid, but most of it is completely above my head.
Saying "here are items, here are a set of properties you can define relating to them, here's some notes on how to use properties" is going to get a lot more people able to contribute than if they need to start understanding theoretical aspects of semantic relationships...
Definitely, I cannot agree more. TBH, the original question of this thread was already settled some messages ago. I understand that it might result confusing that we have wandered off into other realms, so I consider that it is better to consider this thread closed and I will consider opening a new one with the right topic (which is quite different as it started :-P)
Cheers, Micru
And to summarize the answer of the original question to future readers. The point of properties is: a) to help humans to better understand Wikidata b) to help programmers (also humans :P) build the software running it c) to make a distinction between concepts found in the world and the concepts that have been "interiorized" by the community
There might be more, but those are the main points that suggest that it is better to keep properties and items separate even if their essence is the same.
Thank you all for this learning experience :-)
Micru
Hi David,
Interesting remark. Let's explore this idea a bit. I will give you two main reasons why we have properties separate, one practical and one conceptual.
First the practical point. Certainly, everything that is used as a property needs to have a datatype, since otherwise the wiki would not know what kind of input UI to show. So you cannot use just any item as a property straight away -- it needs to have a datatype first. So, yes, you could abolish the namespace Property but you still would have a clear, crisp distinction between property items (those with datatype) and normal items (those without a datatype). Because of this, most of the other functions would work the same as before (for example, property autocompletion would still only show properties, not arbitrary items).
A complication with this approach is that property datatypes cannot change in Wikibase. This design was picked since there is no way to convert existing data from one datatype to another in general. So changing the datatype would create problems by making a lot of data "invalid", and require special handling and special UI to handle this situation. With properties living in a separate namespace, this is not a real restriction: you can just create a new property and give it the same label (after naming the old one differently, e.g., putting "DEPRECATED" in its name). Then you can migrate the data in some custom fashion. But if properties would be items, we would have a problem here: the item is already linked to many Wikipedias and other projects, and it might be used in LUA scripts, queries, or even external applications like Denny's Javascript translation library. You cannot change item ids easily. Also, many items would not have a datatype, so the first one who (accidentally?) is entered will be fixed. So we would definitely need to rethink the whole idea of unchangeable datatypes.
My other important reason is conceptual. Properties are not considered part of the (encyclopaedic) data but rather part of the schema that the community has picked to organise that data. As in your example, "emissivity" (Q899670) is a notion in physics as described in a Wikipedia article. There are many things to say about this notion (for example, it has a history: somebody must have defined this first -- although Wikipedia does not say it in this case). As in all cases, some statements might be disputed while others are widely acknowledged to be "true".
For the property "emissivity" (P1295), the situation is quite different. It was introduced as an element used to enter data, similar to a row in a database table or an infobox template in some Wikipedia. It does probably closely relate to the actual physical notion Q899670, but it still is a different thing. For example, it was first introduced by User:Jakec, who is probably not the person who introduced the physical concept ;-) Anything that we will say about P1295 in the future refers to the property -- a concept of our own making, that is not described in any external source (there are no publications discussing P1295).
This is also the reason why properties are supposed to support *claims* not *statements*. That is, they will have property-value pairs and qualifiers, but no references or ranks. Indeed, anything we say about properties has the status of a definition. If we say it, it's true. There is no other authority on Wikidata properties. You could of course still have items and properties "share" a page and somehow define which statements/claims refer to which concept, but this does not seem to make things easier for users.
These are, for me, the two main reasons why it makes sense to keep properties apart from items on a technical level. Besides this, it is also convenient to separate the 1000-something properties from the 15-million something items for reasons of maintenance.
Best regards,
Markus
On 28/05/14 09:25, David Cuenca wrote:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
Markus, The explanation about the implications of renaming/deleting makes most sense and just that justifies already the separation in two. It is equally true that when we create a property, we might have "cleaned" the original concept so much that it might differ (even slightly) with the understood concept that the item represents. However, even after that process, the "new" concept is still an item...
The process of imbuing a concept with permanent characteristics (adding a datatype) and the practical approach, also seems to recommend keeping items and properties separate. Thanks for showing me that reasoning :)
I am still wondering about how are we going to classify properties. Maybe it will require a broader discussion, but if they are the same (or mostly the same) as items, then we can just link them as "same as", and build the classing structure just for the items. OTOH, if they are different, then we will need to mirror that classification for properties, which seems quite redundant. Plus adding a new datatype, "property".
All in all, my conclusion about this is that properties are just concepts with special qualities that justify the separation in the software (even if in real life there is no separation).
many thanks for your detailed answer, and sorry if I'm bringing up already discussed topics. It is just that when you stare long into wikidata, wikidata stares back into you ;)
Cheers, Micru
On Wed, May 28, 2014 at 11:39 AM, Markus Krötzsch < markus@semantic-mediawiki.org> wrote:
Hi David,
Interesting remark. Let's explore this idea a bit. I will give you two main reasons why we have properties separate, one practical and one conceptual.
First the practical point. Certainly, everything that is used as a property needs to have a datatype, since otherwise the wiki would not know what kind of input UI to show. So you cannot use just any item as a property straight away -- it needs to have a datatype first. So, yes, you could abolish the namespace Property but you still would have a clear, crisp distinction between property items (those with datatype) and normal items (those without a datatype). Because of this, most of the other functions would work the same as before (for example, property autocompletion would still only show properties, not arbitrary items).
A complication with this approach is that property datatypes cannot change in Wikibase. This design was picked since there is no way to convert existing data from one datatype to another in general. So changing the datatype would create problems by making a lot of data "invalid", and require special handling and special UI to handle this situation. With properties living in a separate namespace, this is not a real restriction: you can just create a new property and give it the same label (after naming the old one differently, e.g., putting "DEPRECATED" in its name). Then you can migrate the data in some custom fashion. But if properties would be items, we would have a problem here: the item is already linked to many Wikipedias and other projects, and it might be used in LUA scripts, queries, or even external applications like Denny's Javascript translation library. You cannot change item ids easily. Also, many items would not have a datatype, so the first one who (accidentally?) is entered will be fixed. So we would definitely need to rethink the whole idea of unchangeable datatypes.
My other important reason is conceptual. Properties are not considered part of the (encyclopaedic) data but rather part of the schema that the community has picked to organise that data. As in your example, "emissivity" (Q899670) is a notion in physics as described in a Wikipedia article. There are many things to say about this notion (for example, it has a history: somebody must have defined this first -- although Wikipedia does not say it in this case). As in all cases, some statements might be disputed while others are widely acknowledged to be "true".
For the property "emissivity" (P1295), the situation is quite different. It was introduced as an element used to enter data, similar to a row in a database table or an infobox template in some Wikipedia. It does probably closely relate to the actual physical notion Q899670, but it still is a different thing. For example, it was first introduced by User:Jakec, who is probably not the person who introduced the physical concept ;-) Anything that we will say about P1295 in the future refers to the property -- a concept of our own making, that is not described in any external source (there are no publications discussing P1295).
This is also the reason why properties are supposed to support *claims* not *statements*. That is, they will have property-value pairs and qualifiers, but no references or ranks. Indeed, anything we say about properties has the status of a definition. If we say it, it's true. There is no other authority on Wikidata properties. You could of course still have items and properties "share" a page and somehow define which statements/claims refer to which concept, but this does not seem to make things easier for users.
These are, for me, the two main reasons why it makes sense to keep properties apart from items on a technical level. Besides this, it is also convenient to separate the 1000-something properties from the 15-million something items for reasons of maintenance.
Best regards,
Markus
On 28/05/14 09:25, David Cuenca wrote:
Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54
Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints?
Cheers, Micru
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
Wikidata-l mailing list Wikidata-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-l
David,
Regarding the question of how to classify properties and how to relate them to items:
* "same as" (in the sense of owl:sameAs) is not the right concept here. In fact, it has often been discouraged to use this on the Web, since it has very strong implications: it means that in all uses of the one identifier, one could just as well use the other identifier, and that it is indistinguishable if something has been said about the one or the other. That seems too strong here, at least for most cases.
* In the world of OWL DL, sameAs specifically refers to individuals, not to classes or properties. Saying "P sameAs Q" does not imply that P and Q have the same extension as properties. For the latter, OWL has the relationship owl:equivalentProperties. This distinction of instance level and schema level is similar to the distinction we have between "instance of" and "subclass of".
* Therefore, I would suggest to use a property called "subproperty of" as one way of relating properties (analogously to "subclass of"). It has to be checked if this actually occurs in Wikidata (do we have any properties that would be in this relation, or do we make it a modelling principle to have only the most specific properties in Wikidata?).
* The relationship from properties to items could be modelled with the existing property "subject of" (P805).
* It might be useful to also have a taxonomic classification of properties. For example, we already group properties into properties for "people", "organisations", etc. Such information could also be added with a specific property (this would be a bit more like a "category" system on property pages). On the other hand, some of this might coincide with constraint information that could be expressed as claims. For instance, person properties might be those with "Type" (i.e., "rdfs:domain") constraint human. By the way, our constraint system could use some systematisation -- there are many overlaps in what you can do with one constraint or another.
Cheers,
Markus
On 28/05/14 12:14, David Cuenca wrote:
Markus, The explanation about the implications of renaming/deleting makes most sense and just that justifies already the separation in two. It is equally true that when we create a property, we might have "cleaned" the original concept so much that it might differ (even slightly) with the understood concept that the item represents. However, even after that process, the "new" concept is still an item...
The process of imbuing a concept with permanent characteristics (adding a datatype) and the practical approach, also seems to recommend keeping items and properties separate. Thanks for showing me that reasoning :)
I am still wondering about how are we going to classify properties. Maybe it will require a broader discussion, but if they are the same (or mostly the same) as items, then we can just link them as "same as", and build the classing structure just for the items. OTOH, if they are different, then we will need to mirror that classification for properties, which seems quite redundant. Plus adding a new datatype, "property".
All in all, my conclusion about this is that properties are just concepts with special qualities that justify the separation in the software (even if in real life there is no separation).
many thanks for your detailed answer, and sorry if I'm bringing up already discussed topics. It is just that when you stare long into wikidata, wikidata stares back into you ;)
Cheers, Micru
On Wed, May 28, 2014 at 11:39 AM, Markus Krötzsch <markus@semantic-mediawiki.org mailto:markus@semantic-mediawiki.org> wrote:
Hi David, Interesting remark. Let's explore this idea a bit. I will give you two main reasons why we have properties separate, one practical and one conceptual. First the practical point. Certainly, everything that is used as a property needs to have a datatype, since otherwise the wiki would not know what kind of input UI to show. So you cannot use just any item as a property straight away -- it needs to have a datatype first. So, yes, you could abolish the namespace Property but you still would have a clear, crisp distinction between property items (those with datatype) and normal items (those without a datatype). Because of this, most of the other functions would work the same as before (for example, property autocompletion would still only show properties, not arbitrary items). A complication with this approach is that property datatypes cannot change in Wikibase. This design was picked since there is no way to convert existing data from one datatype to another in general. So changing the datatype would create problems by making a lot of data "invalid", and require special handling and special UI to handle this situation. With properties living in a separate namespace, this is not a real restriction: you can just create a new property and give it the same label (after naming the old one differently, e.g., putting "DEPRECATED" in its name). Then you can migrate the data in some custom fashion. But if properties would be items, we would have a problem here: the item is already linked to many Wikipedias and other projects, and it might be used in LUA scripts, queries, or even external applications like Denny's Javascript translation library. You cannot change item ids easily. Also, many items would not have a datatype, so the first one who (accidentally?) is entered will be fixed. So we would definitely need to rethink the whole idea of unchangeable datatypes. My other important reason is conceptual. Properties are not considered part of the (encyclopaedic) data but rather part of the schema that the community has picked to organise that data. As in your example, "emissivity" (Q899670) is a notion in physics as described in a Wikipedia article. There are many things to say about this notion (for example, it has a history: somebody must have defined this first -- although Wikipedia does not say it in this case). As in all cases, some statements might be disputed while others are widely acknowledged to be "true". For the property "emissivity" (P1295), the situation is quite different. It was introduced as an element used to enter data, similar to a row in a database table or an infobox template in some Wikipedia. It does probably closely relate to the actual physical notion Q899670, but it still is a different thing. For example, it was first introduced by User:Jakec, who is probably not the person who introduced the physical concept ;-) Anything that we will say about P1295 in the future refers to the property -- a concept of our own making, that is not described in any external source (there are no publications discussing P1295). This is also the reason why properties are supposed to support *claims* not *statements*. That is, they will have property-value pairs and qualifiers, but no references or ranks. Indeed, anything we say about properties has the status of a definition. If we say it, it's true. There is no other authority on Wikidata properties. You could of course still have items and properties "share" a page and somehow define which statements/claims refer to which concept, but this does not seem to make things easier for users. These are, for me, the two main reasons why it makes sense to keep properties apart from items on a technical level. Besides this, it is also convenient to separate the 1000-something properties from the 15-million something items for reasons of maintenance. Best regards, Markus On 28/05/14 09:25, David Cuenca wrote: Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words. But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54 Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints? Cheers, Micru _________________________________________________ Wikidata-l mailing list Wikidata-l@lists.wikimedia.org <mailto:Wikidata-l@lists.wikimedia.org> https://lists.wikimedia.org/__mailman/listinfo/wikidata-l <https://lists.wikimedia.org/mailman/listinfo/wikidata-l> _________________________________________________ Wikidata-l mailing list Wikidata-l@lists.wikimedia.org <mailto:Wikidata-l@lists.wikimedia.org> https://lists.wikimedia.org/__mailman/listinfo/wikidata-l <https://lists.wikimedia.org/mailman/listinfo/wikidata-l>-- Etiamsi omnes, ego non
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On Wed, May 28, 2014 at 2:48 PM, Markus Krötzsch markus@semantic-mediawiki.org wrote:
David,
Regarding the question of how to classify properties and how to relate them to items:
- "same as" (in the sense of owl:sameAs) is not the right concept here. In
fact, it has often been discouraged to use this on the Web, since it has very strong implications: it means that in all uses of the one identifier, one could just as well use the other identifier, and that it is indistinguishable if something has been said about the one or the other. That seems too strong here, at least for most cases.
- In the world of OWL DL, sameAs specifically refers to individuals, not to
classes or properties. Saying "P sameAs Q" does not imply that P and Q have the same extension as properties. For the latter, OWL has the relationship owl:equivalentProperties. This distinction of instance level and schema level is similar to the distinction we have between "instance of" and "subclass of".
- Therefore, I would suggest to use a property called "subproperty of" as
one way of relating properties (analogously to "subclass of"). It has to be checked if this actually occurs in Wikidata (do we have any properties that would be in this relation, or do we make it a modelling principle to have only the most specific properties in Wikidata?).
- The relationship from properties to items could be modelled with the
existing property "subject of" (P805).
- It might be useful to also have a taxonomic classification of properties.
For example, we already group properties into properties for "people", "organisations", etc. Such information could also be added with a specific property (this would be a bit more like a "category" system on property pages).
Yes. That's the way forward for now.
On the other hand, some of this might coincide with constraint information that could be expressed as claims. For instance, person properties might be those with "Type" (i.e., "rdfs:domain") constraint human. By the way, our constraint system could use some systematisation -- there are many overlaps in what you can do with one constraint or another.
I hope to have a team of students work on improving constraints reports and everything around it later in the year. It'll depend on if they pick this project though.
Cheers Lydia
Markus,
Ok, now I understand that "same as" wouldn't be a good name for the confusion it would cause. However the property "subject of" as it is now wouldn't be a good candidate either. Its meaning is that a certain statement is represented by another item (that is why it is only allowed to be used as qualifier).
Perhaps a better name would be "corresponds with item" and the inverse "corresponds with property". Just by having these connections, a lot of information can be inferred from the connected item.
Consider the following example with "occupation (P106)", and "occupation (Q13516667)": - I cannot find any clear "subproperty of" for p106, but there is a clear "subclass of:human behaviour" for the item - "human behaviour" is "part of" human - "human" can have a statement "intrinsic property" (property proposal still under discussion) with values "birthday (Q47223)" and an "(eventual) date of death". It can be expanded in the future to include newly created properties like "height", "weight", "eye color", etc - birthday (Q47223) <corresponds with property> date of birth (P569)
Out of this I reach the following conclusions: - the taxonomy of properties is going to be weak, since there is not always a clear subpropertyOf unless created artificially (more work) - the standard taxonomy of items (subclass of/part of) is sufficient to automatically reach meaningful constraints and inference (less work) - by adding manually the constraints to the property itself we are duplicating information which will require volunteer effort to maintain (more work)
My recommendation is to rely mainly on the main taxonomy instead of creating a parallel property taxonomy, and then think of ways to extract information from the main taxonomy to convert it automatically into constraints. All the maintenance takes effort, so the more it can be automated, the more efficient volunteers will be. And if we can simplify the maintenance of properties, we will be able to simplify the creation of properties too, specially when we face the next surge which will come with the datatype "number with units".
Cheers, Micru
On Wed, May 28, 2014 at 2:48 PM, Markus Krötzsch < markus@semantic-mediawiki.org> wrote:
David,
Regarding the question of how to classify properties and how to relate them to items:
- "same as" (in the sense of owl:sameAs) is not the right concept here. In
fact, it has often been discouraged to use this on the Web, since it has very strong implications: it means that in all uses of the one identifier, one could just as well use the other identifier, and that it is indistinguishable if something has been said about the one or the other. That seems too strong here, at least for most cases.
- In the world of OWL DL, sameAs specifically refers to individuals, not
to classes or properties. Saying "P sameAs Q" does not imply that P and Q have the same extension as properties. For the latter, OWL has the relationship owl:equivalentProperties. This distinction of instance level and schema level is similar to the distinction we have between "instance of" and "subclass of".
- Therefore, I would suggest to use a property called "subproperty of" as
one way of relating properties (analogously to "subclass of"). It has to be checked if this actually occurs in Wikidata (do we have any properties that would be in this relation, or do we make it a modelling principle to have only the most specific properties in Wikidata?).
- The relationship from properties to items could be modelled with the
existing property "subject of" (P805).
- It might be useful to also have a taxonomic classification of
properties. For example, we already group properties into properties for "people", "organisations", etc. Such information could also be added with a specific property (this would be a bit more like a "category" system on property pages). On the other hand, some of this might coincide with constraint information that could be expressed as claims. For instance, person properties might be those with "Type" (i.e., "rdfs:domain") constraint human. By the way, our constraint system could use some systematisation -- there are many overlaps in what you can do with one constraint or another.
Cheers,
Markus
On 28/05/14 12:14, David Cuenca wrote:
Markus, The explanation about the implications of renaming/deleting makes most sense and just that justifies already the separation in two. It is equally true that when we create a property, we might have "cleaned" the original concept so much that it might differ (even slightly) with the understood concept that the item represents. However, even after that process, the "new" concept is still an item...
The process of imbuing a concept with permanent characteristics (adding a datatype) and the practical approach, also seems to recommend keeping items and properties separate. Thanks for showing me that reasoning :)
I am still wondering about how are we going to classify properties. Maybe it will require a broader discussion, but if they are the same (or mostly the same) as items, then we can just link them as "same as", and build the classing structure just for the items. OTOH, if they are different, then we will need to mirror that classification for properties, which seems quite redundant. Plus adding a new datatype, "property".
All in all, my conclusion about this is that properties are just concepts with special qualities that justify the separation in the software (even if in real life there is no separation).
many thanks for your detailed answer, and sorry if I'm bringing up already discussed topics. It is just that when you stare long into wikidata, wikidata stares back into you ;)
Cheers, Micru
On Wed, May 28, 2014 at 11:39 AM, Markus Krötzsch <markus@semantic-mediawiki.org mailto:markus@semantic-mediawiki.org>
wrote:
Hi David, Interesting remark. Let's explore this idea a bit. I will give you two main reasons why we have properties separate, one practical and one conceptual. First the practical point. Certainly, everything that is used as a property needs to have a datatype, since otherwise the wiki would not know what kind of input UI to show. So you cannot use just any item as a property straight away -- it needs to have a datatype first. So, yes, you could abolish the namespace Property but you still would have a clear, crisp distinction between property items (those with datatype) and normal items (those without a datatype). Because of this, most of the other functions would work the same as before (for example, property autocompletion would still only show properties, not arbitrary items). A complication with this approach is that property datatypes cannot change in Wikibase. This design was picked since there is no way to convert existing data from one datatype to another in general. So changing the datatype would create problems by making a lot of data "invalid", and require special handling and special UI to handle this situation. With properties living in a separate namespace, this is not a real restriction: you can just create a new property and give it the same label (after naming the old one differently, e.g., putting "DEPRECATED" in its name). Then you can migrate the data in some custom fashion. But if properties would be items, we would have a problem here: the item is already linked to many Wikipedias and other projects, and it might be used in LUA scripts, queries, or even external applications like Denny's Javascript translation library. You cannot change item ids easily. Also, many items would not have a datatype, so the first one who (accidentally?) is entered will be fixed. So we would definitely need to rethink the whole idea of unchangeable datatypes. My other important reason is conceptual. Properties are not considered part of the (encyclopaedic) data but rather part of the schema that the community has picked to organise that data. As in your example, "emissivity" (Q899670) is a notion in physics as described in a Wikipedia article. There are many things to say about this notion (for example, it has a history: somebody must have defined this first -- although Wikipedia does not say it in this case). As in all cases, some statements might be disputed while others are widely acknowledged to be "true". For the property "emissivity" (P1295), the situation is quite different. It was introduced as an element used to enter data, similar to a row in a database table or an infobox template in some Wikipedia. It does probably closely relate to the actual physical notion Q899670, but it still is a different thing. For example, it was first introduced by User:Jakec, who is probably not the person who introduced the physical concept ;-) Anything that we will say about P1295 in the future refers to the property -- a concept of our own making, that is not described in any external source (there are no publications discussing P1295). This is also the reason why properties are supposed to support *claims* not *statements*. That is, they will have property-value pairs and qualifiers, but no references or ranks. Indeed, anything we say about properties has the status of a definition. If we say it, it's true. There is no other authority on Wikidata properties. You could of course still have items and properties "share" a page and somehow define which statements/claims refer to which concept, but this does not seem to make things easier for users. These are, for me, the two main reasons why it makes sense to keep properties apart from items on a technical level. Besides this, it is also convenient to separate the 1000-something properties from the 15-million something items for reasons of maintenance. Best regards, Markus On 28/05/14 09:25, David Cuenca wrote: Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages,the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words.
But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54 Am I missing something here? Are properties really needed or arewe adding unnecessary artificial constraints?
Cheers, Micru _________________________________________________ Wikidata-l mailing list Wikidata-l@lists.wikimedia.org <mailto:Wikidata-l@lists.wikimedia.org> https://lists.wikimedia.org/__mailman/listinfo/wikidata-l <https://lists.wikimedia.org/mailman/listinfo/wikidata-l> _________________________________________________ Wikidata-l mailing list Wikidata-l@lists.wikimedia.org <mailto:Wikidata-l@lists.wikimedia.orghttps://lists.wikimedia.org/__mailman/listinfo/wikidata-l <https://lists.wikimedia.org/mailman/listinfo/wikidata-l>-- Etiamsi omnes, ego non
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David,
On 28/05/14 16:35, David Cuenca wrote:
Markus,
Ok, now I understand that "same as" wouldn't be a good name for the confusion it would cause. However the property "subject of" as it is now wouldn't be a good candidate either. Its meaning is that a certain statement is represented by another item (that is why it is only allowed to be used as qualifier).
Ok.
Perhaps a better name would be "corresponds with item" and the inverse "corresponds with property". Just by having these connections, a lot of information can be inferred from the connected item.
Consider the following example with "occupation (P106)", and "occupation (Q13516667)":
- I cannot find any clear "subproperty of" for p106, but there is a
clear "subclass of:human behaviour" for the item
- "human behaviour" is "part of" human
I don't understand this use of "part of". Maybe I would say "having an occupation is part of being human" but not that "occupation is part of human". I would not use either of these and restrict "part of" to clear, undisputed statements like "the steering wheel is part of the car". Otherwise, anything could be part of human ("head"?, "sadness"?, "singing"?, "birth"? -- entering this in Wikidata would not lead anywhere).
"Part of" is quite problematic in general. You can see it from the discussion on its property page, and also from the uses it sees in the wiki, that this property is severely misunderstood and/or misused. At the very least, one should distinguish "physical part of" from "meronym" (both are aliases of the property now!). And then one should realise that meronyms are in the domain of Wiktionary, which we cannot capture in Wikidata properly since we do not have items for words but for concepts. One alias for an item might be a meronym of something else, while another alias for the same item is not. Using statements for linguistic properties in Wikidata will not be successful. I am not saying that Wikibase is not able to capture some ideas of a thesaurus (we have actually discussed this), but this is not how it is used in Wikidata.
- "human" can have a statement "intrinsic property" (property proposal
still under discussion) with values "birthday (Q47223)" and an "(eventual) date of death". It can be expanded in the future to include newly created properties like "height", "weight", "eye color", etc
Yes, this again makes sense to me. It is basically a variant of the constraint "Item" which allows you to say that items that are instance of human should also have a birthday. But again, this is schematic information (like constraints) and it should not be mixed up with actual data. It is the same conceptual difference that I have explained for properties vs. items earlier. Moreover, I think this information (even if correct in some sense) has very little utility as a piece of information about an item; it is much more useful for constraints about properties (which are not items).
- birthday (Q47223) <corresponds with property> date of birth (P569)
It should be the other way around: the correspondence says something about P569, not about Q47223. There cannot be any reference for this. It should therefore be a claim on the page of P569 rather than a statement on the page of Q47223.
Out of this I reach the following conclusions:
- the taxonomy of properties is going to be weak, since there is not
always a clear subpropertyOf unless created artificially (more work)
I agree.
- the standard taxonomy of items (subclass of/part of) is sufficient
to automatically reach meaningful constraints and inference (less work)
I agree that the taxonomy will be helpful in constraints. This is what constraints already do when using instance of/subclass of. However, I do not agree that the constraints can or should be stated as part of this taxonomy. Constraints are too complex, and they are conceptually different (they say how a property should be used, not how something in the Real World relates to something else). Constraints interact nicely with the taxonomy and help to get useful conclusions, but they are not "part of" taxonomy ;-). We must keep content organisation separate from content.
- by adding manually the constraints to the property itself we are
duplicating information which will require volunteer effort to maintain (more work)
I disagree. Constraints refer to the property, not to the Wikidata item, and it would be conceptually wrong to mix these things up. We already have agreed that properties and items need to remain distinct for technical reasons. Once this is clear, there is no reason to move information that refers to properties (constraints) to item pages. This will not be a duplication of information: it is enough to have the constraints on the property pages only. If you look at the constraints we have, you can see many examples that are specific to Wikidata and certainly not a general thing about the concept (take the "allowed values" for "sex or gender"). We really want to keep editorial helpers (constraints) distinct from sourced information (statements about items).
My recommendation is to rely mainly on the main taxonomy instead of creating a parallel property taxonomy, and then think of ways to extract information from the main taxonomy to convert it automatically into constraints. All the maintenance takes effort, so the more it can be automated, the more efficient volunteers will be. And if we can simplify the maintenance of properties, we will be able to simplify the creation of properties too, specially when we face the next surge which will come with the datatype "number with units".
I agree with the general goals, but I don't think that things become any easier if we confuse information about properties with information about items. We can still re-use information we have about items (like the class hierarchy that we already use in constraints) to avoid duplication, but some things are clearly not part of the item taxonomy.
Cheers,
Markus
On Wed, May 28, 2014 at 2:48 PM, Markus Krötzsch <markus@semantic-mediawiki.org mailto:markus@semantic-mediawiki.org> wrote:
David, Regarding the question of how to classify properties and how to relate them to items: * "same as" (in the sense of owl:sameAs) is not the right concept here. In fact, it has often been discouraged to use this on the Web, since it has very strong implications: it means that in all uses of the one identifier, one could just as well use the other identifier, and that it is indistinguishable if something has been said about the one or the other. That seems too strong here, at least for most cases. * In the world of OWL DL, sameAs specifically refers to individuals, not to classes or properties. Saying "P sameAs Q" does not imply that P and Q have the same extension as properties. For the latter, OWL has the relationship owl:equivalentProperties. This distinction of instance level and schema level is similar to the distinction we have between "instance of" and "subclass of". * Therefore, I would suggest to use a property called "subproperty of" as one way of relating properties (analogously to "subclass of"). It has to be checked if this actually occurs in Wikidata (do we have any properties that would be in this relation, or do we make it a modelling principle to have only the most specific properties in Wikidata?). * The relationship from properties to items could be modelled with the existing property "subject of" (P805). * It might be useful to also have a taxonomic classification of properties. For example, we already group properties into properties for "people", "organisations", etc. Such information could also be added with a specific property (this would be a bit more like a "category" system on property pages). On the other hand, some of this might coincide with constraint information that could be expressed as claims. For instance, person properties might be those with "Type" (i.e., "rdfs:domain") constraint human. By the way, our constraint system could use some systematisation -- there are many overlaps in what you can do with one constraint or another. Cheers, Markus On 28/05/14 12:14, David Cuenca wrote: Markus, The explanation about the implications of renaming/deleting makes most sense and just that justifies already the separation in two. It is equally true that when we create a property, we might have "cleaned" the original concept so much that it might differ (even slightly) with the understood concept that the item represents. However, even after that process, the "new" concept is still an item... The process of imbuing a concept with permanent characteristics (adding a datatype) and the practical approach, also seems to recommend keeping items and properties separate. Thanks for showing me that reasoning :) I am still wondering about how are we going to classify properties. Maybe it will require a broader discussion, but if they are the same (or mostly the same) as items, then we can just link them as "same as", and build the classing structure just for the items. OTOH, if they are different, then we will need to mirror that classification for properties, which seems quite redundant. Plus adding a new datatype, "property". All in all, my conclusion about this is that properties are just concepts with special qualities that justify the separation in the software (even if in real life there is no separation). many thanks for your detailed answer, and sorry if I'm bringing up already discussed topics. It is just that when you stare long into wikidata, wikidata stares back into you ;) Cheers, Micru On Wed, May 28, 2014 at 11:39 AM, Markus Krötzsch <markus@semantic-mediawiki.org <mailto:markus@semantic-mediawiki.org> <mailto:markus@semantic-__mediawiki.org <mailto:markus@semantic-mediawiki.org>>> wrote: Hi David, Interesting remark. Let's explore this idea a bit. I will give you two main reasons why we have properties separate, one practical and one conceptual. First the practical point. Certainly, everything that is used as a property needs to have a datatype, since otherwise the wiki would not know what kind of input UI to show. So you cannot use just any item as a property straight away -- it needs to have a datatype first. So, yes, you could abolish the namespace Property but you still would have a clear, crisp distinction between property items (those with datatype) and normal items (those without a datatype). Because of this, most of the other functions would work the same as before (for example, property autocompletion would still only show properties, not arbitrary items). A complication with this approach is that property datatypes cannot change in Wikibase. This design was picked since there is no way to convert existing data from one datatype to another in general. So changing the datatype would create problems by making a lot of data "invalid", and require special handling and special UI to handle this situation. With properties living in a separate namespace, this is not a real restriction: you can just create a new property and give it the same label (after naming the old one differently, e.g., putting "DEPRECATED" in its name). Then you can migrate the data in some custom fashion. But if properties would be items, we would have a problem here: the item is already linked to many Wikipedias and other projects, and it might be used in LUA scripts, queries, or even external applications like Denny's Javascript translation library. You cannot change item ids easily. Also, many items would not have a datatype, so the first one who (accidentally?) is entered will be fixed. So we would definitely need to rethink the whole idea of unchangeable datatypes. My other important reason is conceptual. Properties are not considered part of the (encyclopaedic) data but rather part of the schema that the community has picked to organise that data. As in your example, "emissivity" (Q899670) is a notion in physics as described in a Wikipedia article. There are many things to say about this notion (for example, it has a history: somebody must have defined this first -- although Wikipedia does not say it in this case). As in all cases, some statements might be disputed while others are widely acknowledged to be "true". For the property "emissivity" (P1295), the situation is quite different. It was introduced as an element used to enter data, similar to a row in a database table or an infobox template in some Wikipedia. It does probably closely relate to the actual physical notion Q899670, but it still is a different thing. For example, it was first introduced by User:Jakec, who is probably not the person who introduced the physical concept ;-) Anything that we will say about P1295 in the future refers to the property -- a concept of our own making, that is not described in any external source (there are no publications discussing P1295). This is also the reason why properties are supposed to support *claims* not *statements*. That is, they will have property-value pairs and qualifiers, but no references or ranks. Indeed, anything we say about properties has the status of a definition. If we say it, it's true. There is no other authority on Wikidata properties. You could of course still have items and properties "share" a page and somehow define which statements/claims refer to which concept, but this does not seem to make things easier for users. These are, for me, the two main reasons why it makes sense to keep properties apart from items on a technical level. Besides this, it is also convenient to separate the 1000-something properties from the 15-million something items for reasons of maintenance. Best regards, Markus On 28/05/14 09:25, David Cuenca wrote: Since the very beginning I have kept myself busy with properties, thinking about which ones fit, which ones are missing to better describe reality, how integrate into the ones that we have. The thing is that the more I work with them, the less difference I see with normal items.... and if soon there will be statements allowed in property pages, the difference will blur even more. I can understand that from the software development point of view it might make sense to have a clear difference. Or for the community to get a deeper understanding of the underlying concepts represented by words. But semantically I see no difference between: cement (Q45190) <emissivity (P1295)> 0.54 and cement (Q45190) <emissivity (Q899670)> 0.54 Am I missing something here? Are properties really needed or are we adding unnecessary artificial constraints? 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Hello, Concerning the use of owl:sameAs http://www.w3.org/TR/owl-ref/#IndividualIdentity, it is used in dbpedia to "link" for instance http://dbpedia.org/page/Joseph_Hocking to its equivalent in Freebase, WikiData and Yago. If we refer to your remark, Markus, this is not an example to follow ?
If the use of owl:sameAs http://www.w3.org/TR/owl-ref/#IndividualIdentity is discouraged, what is its purpose and in which case could it be used ? Does this means that OWL lacks a proper way to interlink ressources from different editors ?
By the way, is the notion of "individuals" an OWL concept ?
Alternative ways to interlink data could also be found on : http://notes.3kbo.com/owl-sameas.
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