Analyzing Schema.org by Peter F. Patel-Schneider.
Abstract:
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.
Peter’s analysis is summarized when he says:
The lack of a complete definition of schema.org limits the possibility of extracting the correct information from web pages that have schema.org markup.
Ah, yes, “…the correct information from web pages….”
I suspect the lack of semantic precision has powered the success of schema.org. Each user of schema.org markup has their private notion of the meaning of their use of the markup and there is no formal definition to disabuse them of that notion. Not that formal definitions were enough to save owl:sameAs from varying interpretations.
Schema.org empowers varying interpretations without requiring users to ignore OWL or description logic.
For the domains that schema.org covers, eateries, movies, bars, whore houses, etc., the semantic slippage permitted by schema.org lowers the bar to usage of its markup. Which has resulted in its adoption more widely than other proposals.
The lesson of schema.org is the degree of semantic slippage you can tolerate depends upon your domain. For pharmaceuticals, I would assume that degree of slippage is as close to zero as possible. For movie reviews, not so much.
Any effort to impose the same degree of semantic slippage across all domains is doomed to failure.
I first saw this in a tweet by Bob DuCharme.