Re: keys for properties
For now the following solution seems to be the simplest:
* make labels for properties be unique for a given language
In that case they can be used as keys. Every wiki has one (and exactly one) site language. If the label is unique, a property can be addressed by languagecode + label,and the languagecode could be used per default inside a wiki. No extra keys per site would be needed, which would have otherwise been provided by the sitelink data (which would be more appropriately named sitekey instead of sitelinks in that case). The description is not used to identify properties by the machine.
This means that two different properties cannot have the same name in one language. We will need to figure out if this is a problem during usage, and if it is, change it later.
I hope this makes sense, Denny
2012/9/17 Markus Krötzsch markus@semantic-mediawiki.org:
On 17/09/12 12:54, Jeroen De Dauw wrote:
Hey,
As explained in the text, the aliases are not distinguished from other property values in the data model right now. This was the status of the discussion when we last talked about this, but we can also re-introduce aliases as a special field (I see why this would be useful). Daniel had an argument against this, saying that many other property values could also work as aliases in certain domains (e.g. binomial names of biological species). So the special status of the alias in the data model was questioned.Right, that makes sense to implement at some point if there really is demand for this. This is rather harder to implement then what we're currently doing and is blocked by phase 2 stuff and probably phase 3 stuff, while we want to have it in phase 1 already.
A while back we also had a related discussion where Daniel took the position that we should also not have special labels and descriptions. The conclusion of that was that we will have them but that we will make them accessible via the same interface as regular properties (at least for read ops).
Ok, I agree with that. I will change the model to have explicit aliases somewhere.
if two items have the same description, can one of them use an alias
that is the title of the other?
Good question. Right now this is not enforced. Then again, right now aliases are not used anywhere for lookups except in the fulltext search thing, where this restriction is not really relevant. Denny, Daniel, any thoughts on this?
This is also based on a preliminary decision made a while back: the
idea was that properties, while not having Wikipedia articles, will still need unique string identifiers that can be used in wikitext (e.g. queries) where one does not want to address properties by ID or by "label+description" pairs.
This seems odd to me - you sure the term TitleRecord is being used consistently through the data model and this thread? I'm using it as "GlobalSiteId PageName".
Yes, this is what I mean. But PageName is just a string, and does not need to refer to an actual page (or be displayed as a link). It can still be used as a "string key" to refer to the property on a certain site.
I do agree you would probably not want to put label and description in wikitext, and that just the label might or might not be sufficient, even if they are unique per language. If you need an id that really is always unique you can just use the p12345 thing. Since most of the editing of these will happen via GUIs (right?) this seems to be quite acceptable. Or does anybody see a better approach?
Well, the above. It allows you to assign a human-readable key to each property that you can use instead of p12345 and that is still unique for each site. Moreover, this can be done with code that is similar to what we already have for site links in Items (but without linking and thus also without auto completion).
In any case, why would you resort to "GlobalSiteId PageName" rather then "label description"?
Because it is easier. First of all, "label description" is not enough: you need to say which language you talk about to make it a key (this can be guessed from the site, but this is still not a unique selection). Second, you do not need to mention the GlobalSiteId if you are on a site and want to use its own ID. So one addressing method requires one strong key (PageName), the other requires three string keys (language, label, description). The former seems easier.
What makes it so odd is that the "GlobalSiteId PageName" is meant to indicate equivalence of items across sites, which is rather different then using it to identify properties in wikitext.
What you are saying ("equivalence across sites") only is another way to say that "GlobalSiteId PageName" is a key for entities on Wikidata. Such keys can always be used to define equivalence classes (of keys that refer to the same thing); how is that a problem?
It seems that a property could at best have a list of
PropertyValueSnaks (no auxiliary Snaks, no references, no statement rank).
Why not have a list of claims?
Do you think you need auxiliary Snaks there? The step from "list of snaks" to "list of snaks with auxiliary snaks (i.e., claims)" is not hard to make (even later), but I would not make it without a cause. In general, what is the motivation of allowing arbitrary Snaks for properties? Really general annotations (users define properties, e.g., to organise other properties) or merely technical information (some properties need extra information about things like units of measurement)?
Markus
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