Analyzing Schema.org - Peter F. Patel-Schneider - ISWC 2014(About) Schema.org is a way to add machine-understandable information to web pages that is processed by the major search engines to improve search performance. The definition of schema.org is provided as a set of web pages plus a partial mapping into RDF triples with unusual properties, and is incomplete in a number of places. This analysis of and formal semantics for schema.org provides a complete basis for a plausible version of what schema.org should be.
Re: Meaning of property "url" from Ed Summers on 2012-10-23 (email@example.com from October 2012)(About) I prefer to think that url being a property of Thing was an intentional move, because the author chose to sidestep the httpRange-14 issue, and let URLs identify any type of resource, as is the case in Roy Fielding's description of resource (Ed Summers)
So I'd not read too much into 'url'. It's somewhere you can put a Web
identifier for the thing being described. As conventions for this in
the Web standards community mature, we should be able to be more
precise on this. (DanBri)
Schema.org and Pre-Existing Communities(About) one of the key insights of Microdata is that the properties of an item are tightly coupled with the type of the item, so the properties don’t need to be orthogonal with the item type and applicable to items of any type... If you are preparing schema.org in secret, it may look like the right thing to do to create your own item types instead of sticking some new properties onto someone else’s item type.
schema.org - Data Model / Mapping to RDFa 1.1(About) Some good points: The decision to allow multiple domains and ranges was purely pragmatic. While the computational properties of systems with a single domain and range are easier to understand, in practice, this forces the creation of a lot of artifical types, which are there purely to act as the domain/range of some properties.
While we would like all the markup we get to follow the schema, in practice, we expect a lot of data that does not. We expect schema.org properties to be used with new types. We also expect that often, where we expect a property value of type Person, Place, Organization or some other subClassOf Thing, we will get a text string. In the spirit of "some data is better than none", we will accept this markup and do the best we can.