I'd like to restate the initial question.
Why did wikidata choose shex instead of other approaches?
From this very detailed comparison
http://book.validatingrdf.com/bookHtml013.html (thank you Andra!) I could see arguments in both directions. I'm curious to know what swayed the wikidata software team as my group is currently grappling with the same decision.
On Thu, May 30, 2019 at 7:55 AM Peter F. Patel-Schneider < pfpschneider@gmail.com> wrote:
The history of ShEx is quite complex.
I don't think that one can say that there were complete and conforming implementations of ShEx in 2017 because the main ShEX specification, http://shex.io/shex-semantics-20170713/ was ill-founded. I pointed this out in https://lists.w3.org/Archives/Public/public-shex/2018Mar/0008.html
There were several quite different semantics proposed for ShEx somewhat earlier, all with significant problems.
peter
On 5/30/19 12:34 AM, Andra Waagmeester wrote:
I really don't see the issue here. SHACL, like ShEx is a language to
express
data shapes. I adopted using ShEx in a wikidata context 2016 when ShEx
was
demonstrated at a tutorial at the SWAT4HCLS conference [1] in Amsterdam,
where
it was discussed in both a tutorial and a hackathon topic. At that
conferene,
I was convinced that ShEx is helpful in maintaining quality in Wikidata.
ShEx
offers not only the means to validate data shapes in Wikidata, but it
also
provides a way to document how primary data is expressed in Wikidata.
In 2016
I joined the ShEx community group [2]. Since I have been actively using
ShEx
in defining shapes in various projects on Wikidata (e.g. Gene Wiki and Wikicite). It is not that this happened in secrecy. On the contrary, it
was
discussed at both Wikimedia [3,4] and non-Wikimedia events [5,6,7].
It is also not the case that SHACL has not been discussed in this
context, on
the contrary, I have very good memories of a workshop where both were
debated
(see page 24 ;) ) [8]
IMHO the statement that we all should adhere to one standard, simply
because
it is a standard, is not a valid argument. Imagine having to dictate
that we
all should speak English because it is the standard language. In every
single
talk that I have given since 2016, proponents of SHACL have been very
vocal in
asking the same question over and over again "why not SHACL?", where the discussion never went beyond, "You should because it is a standard". It
is
also a bit disingenuous to suggest we all should adhere to SHACL because
it is
the standard, while in the same sentence calling it a "Recommendation".
Although initially, I was open to SHACL as well (I use both Mac and
Linux, so
why not open up to different alternatives in data shapes), (Some)
Arguments
for me to prefer ShEx over SHACL are:
- Already in 2017 there were different (open) implementations. At the
time
SHACL didn't have much tooling to choose from, other than one javascript implementation and a proprietary software package. 2. ShEx has a more intuitive way of describing Shapes, which is the
compact
syntax (ShExC). SHACL seems to have adopted the compact syntax as well,
but
only yesterday [9]. 3. The culture in the Shape Expression community group aligns well with
the
culture in Wikidata. 4. I don't want to be shackled to one standard (pun intended). I assume
the
name was chosen with a shackle in mind, which puts constraints at the
core of
the language. Wikidata already has different methods in place to deal
with
constraints and constraint violations. In the context of Wikidata, ShEx
should
specifically not be intended to impose constraints, on the contrary, it
allows
expressing of disagreement or variants of different shapes, whether
conflict
or not. Which fits well with the NPOV concept. Symbols do matter.
For a less personal comparison, I refer to the "Validating RDF data" book which describes both ShEx and SHACL, and has a specific chapter on how
they
compare and differ [10]
Up until now, I have been using ShEx in repositories outside the Wikidata ecosystem (e.g. Github), but I am really excited about the release of
this
extension. I am curious about how the wiki extension will influence the maintenance of schemas. Schemas are currently often expressed as static images, while in practice the schemas are as fluid as the underlying data itself. Being able to document these changes dynamically (the wiki way),
can
be very interesting. One specific expectation I have is that it might
make it
easier to write federated SPARQL queries. Currently, when writing these federated queries we often have to rely on either a set of example
queries or
a one-time schema description, which makes it hard to write those
queries,
because of schemas changing constantly. Federated SPARQL queries now
really is
a process of "slot machine" querying, where one has to explore the
underlying
schema, query by query. With a wiki in place and a community maintaining these ever-changing schema's, I expect better documentation.
The data shape community, instead of adhering to one language, should
really
be proud to have produced two very helpful languages. ShEx and SHACL are similar but do have differences so both have merit to exist and I wish we could steer away from this ShEx vs SHACL feud. It really isn't helping
the
cause, i.e. being able to express schemas in a formal language.
Honestly, this
fued really reminds me of the famous monty python sketch, "The machine
that
says Bing". Let us focus on the patient and not on the "Bing".
Just my 2ct.
[1] http://www.swat4ls.org/workshops/amsterdam2016/ [2] https://www.w3.org/community/shex/ [3]
https://www.wikidata.org/wiki/Wikidata:WikidataCon_2017/Submissions/Using_Sh...
[4] https://meta.wikimedia.org/wiki/WikiCite_2017/Program [5]
https://figshare.com/articles/Using_Shape_Expressions_ShEx_to_model_validate...
[6]
https://2017.semantics.cc/satellite-events/linked-data-quality-assessment-an...
https://upload.wikimedia.org/wikipedia/commons/d/d6/WikiCite_2017_report.pdf
[9] https://lists.w3.org/Archives/Public/public-shacl/2019May/0012.html [10] http://book.validatingrdf.com/
On Wed, May 29, 2019 at 10:05 PM Antoine Zimmermann <antoine.zimmermann@emse.fr mailto:antoine.zimmermann@emse.fr> wrote:
Hello, Could you explain why the non-standard ShEx has been chosen ratherthan
the W3C Recommendation SHACL? I would assume that if one has several options for bringing a functionality to something that largely promotes interoperability(like
Wikidata), the default choice should be a standard, and /only if/ one has a carefully crafted argumentation to reject it, one would opt for something else. For those who may not know, the W3C RDF Data Shapes Working Groupworked
between 2014 and 2017 on defining a standard for describing datashapes
in RDF. ShEx existed already and was a candidate for standardisation. Eventually, another standard emerged, Shapes Constraint Language(SHACL,
see https://www.w3.org/TR/shacl/). Disclaimer: I did not contribute to either SHACL or ShEx, and I donot
know them enough to judge which one is better. Best, --AZ On 19/05/2019 15:32, Léa Lacroix wrote: > Hello all, > > After several months of development and testing together with the > WikiProject ShEx > <https://www.wikidata.org/wiki/Wikidata:WikiProject_ShEx>, Shape > Expressions are about to be enabled on Wikidata. > > *First of all, what are Shape Expressions?* > > ShEx (Q29377880) <https://www.wikidata.org/wiki/Q29377880> is aconcise,
> formal modeling and validation language for RDF structures. Shape > Expressions can be used to define shapes within the RDF graph. Inthe
> case of Wikidata, this would be sets of properties, qualifiers and > references that describe the domain being modeled. > > See also: > > * a short video about ShEx > <https://www.youtube.com/watch?v=AR75KhEoRKg> made bycommunity
> members during the Wikimedia hackathon 2019 > * introduction to ShEx <http://shex.io/shex-primer/> > * more details about the language <http://shex.io/shex-semantics/%3E
> > *What can it be used for?* > > On Wikidata, the main goal of Shape Expressions would be todescribe
> what the basic structure of an item would be. For example, for ahuman,
> we probably want to have a date of birth, a place of birth, andmany
> other important statements. But we would also like to make surethat if
> a statement with the property “children” exists, the value(s) ofthis
> property should be humans as well. Schemas will describe in detailwhat
> is expected in the structure of items, statements and values ofthese
> statements. > > Once Schemas are created for various types of items, it ispossible to
> test some existing items against the Schema, and highlight possible > errors or lack of information. Subsets of the Wikidata graph can be > tested to see whether or not they conform to a specific shapethrough
> the use of validation tools. Therefore, Schemas will be veryuseful to
> help the editors improving the data quality. We imagine this to be > especially useful for wiki projects to more easily discuss andensure
> the modeling of items in their domain. In the spirit of Wikidatanot
> restricting the world, Shape Expressions are a tool to highlight,not
> prevent, errors. > > On top of this, one could imagine other uses of Schemas in thefuture,
> for example building a tool that would suggest, when creating a new > item, what would be the basic structure for this item, and helping > adding statements or values. A bit like this existing tool, Cradle > <https://tools.wmflabs.org/wikidata-todo/cradle/#/>, that iscurrently
> not based on ShEx. > > *What is going to change on Wikidata?* > > * A new extension will be added to Wikidata: EntitySchema > <https://www.mediawiki.org/wiki/Extension:EntitySchema>,defining
> the Schema namespace and its behavior as well as special pages > related to it. > * A new entity type, EntitySchema, will be enabled to store Shape > Expressions. Schemas will be identified with the letter E. > * The Schemas will have multilingual labels, descriptions andaliases
> (quite similar to the termbox on Items), and the schema textone can
> fill with a syntax called ShEx Compact Syntax (ShExC) > <http://shex.io/shex-semantics/#shexc>. You can see anexample here
> <https://wikidata-shex.wmflabs.org/wiki/EntitySchema:E2>. > * The external tool shex-simple > <https://tools.wmflabs.org/shex-simple/wikidata/packages/shex-webapp/doc/shex...
> is directly linked from the Schema pages in order to checkentities
> of your choice against the schema. > > *When is this happening?* > > Schemas will be enabled on on test.wikidata.org <> <http://test.wikidata.org> on May 21st and on wikidata.org <http://wikidata.org> > <http://wikidata.org> on May 28th. After this release, they willbe
> integrated to the regular maintenance just like the rest ofWikidata’s
> features. > > *How can you help?* > > * Before the release, you can try to edit or create ShapeExpressions
> on our test system <https://wikidata-shex.wmflabs.org/wiki/Main_Page%3E
> * If you find any issue or feature you’d like to have, feel freeto
> create a new task on Phabricator with the tag|shape-expressions|
> * Once Schemas are enabled, you can discuss about it on yourfavorite
> wikiprojects: for example, what types of items would you liketo model?
> * You can also get more information about how to create a Schema > <https://www.wikidata.org/wiki/Wikidata:WikiProject_ShEx/How_to_get_started%3...
> > *See also: * > > * Main Phabricator board > <https://phabricator.wikimedia.org/tag/shape_expressions/> > * Technical documentation of the extension > <https://meta.wikimedia.org/wiki/Extension:EntitySchema> > * To enhance the interface, you can use this user script > <https://www.wikidata.org/wiki/User:Zvpunry/EntitySchemaHighlighter.js%3E
> to highlight items and properties in the schema code and turnthe
> IDs into links > > If you have any questions, feel free to reach me. Cheers, > > -- > Léa Lacroix > Project Manager Community Communication for Wikidata > > Wikimedia Deutschland e.V. > Tempelhofer Ufer 23-24 > 10963 Berlin > www.wikimedia.de <http://www.wikimedia.de> <> > Wikimedia Deutschland - Gesellschaft zur Förderung Freien Wissense. V.
> > Eingetragen im Vereinsregister des AmtsgerichtsBerlin-Charlottenburg
> unter der Nummer 23855 Nz. Als gemeinnützig anerkannt durch das > Finanzamt für Körperschaften I Berlin, Steuernummer 27/029/42207. > > > _______________________________________________ > Wikidata mailing list > Wikidata@lists.wikimedia.org <mailto:Wikidata@lists.wikimedia.org> > https://lists.wikimedia.org/mailman/listinfo/wikidata > _______________________________________________ Wikidata mailing list Wikidata@lists.wikimedia.org <mailto:Wikidata@lists.wikimedia.org> https://lists.wikimedia.org/mailman/listinfo/wikidata
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