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, 

* 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 :-)



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

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
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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