It’s clear from discussion bouncing around IRC, Twitter, Skype and elsewhere that “Lock-in” isn’t a phrase to use lightly.
So I post this to make myself absolutely clear. A few days ago I mentioned in IRC a concern that newcomers to SPARQL and RDF databases might not appreciate which SPARQL extensions are widely implemented, and which are the specialist offerings of the system they happen to be using. I mentioned OpenLink’s Virtuoso in particular as a SPARQL implementation that had a rich and powerful set of extensions.
Since it seems there is some risk I might be mis-interpreted as suggesting OpenLink are actively trying to “do a Microsoft” and trap users in some proprietary pseudo-SPARQL, I’ll state what I took to be obvious background knowledge: OpenLink is a company who owe their success to the promotion of cross-vendor database portability, they have been tireless advocates of a standards-based Semantic Web, and they’re active in proposing extensions to W3C for standardisation. So – no criticism of OpenLink intended. None at all.
All I think we need here, are a few utilities that help developers understand the nature of the various SPARQL dialects and the potential costs/benefits of using them. Perhaps an online validator, alongside those for RDF/XML, RDFa, Turtle etc. Such a validator might usefully list the extensions used in some query, and give pointers (perhaps into a wiki) where the status of the various extensions constructs can be discussed and documented.
Since SPARQL is such a young language, it lacks a lot of things that are taken from granted in the SQL world, and so using rich custom extensions when available is for many developers a sensible choice. My only concern is that it must be a choice, and one entered into consciously.