Quick clarification on SPARQL extensions and “Lock-in”

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.

Visual SPARQL query tools

Quick links – thinking about tools that allow graphical SPARQL query authoring…

OpenLink Virtuoso: InteractiveSparqlQueryBuilder (in HTML/CSS/.js). Pictured below; extensive documentation and screenshots linked from their main page.

…an ancestor of which was Damian Steer’s RDFAuthor tool for MacOSX, which could generate Squish (a SPARQL precursor) and query services over the ‘array of hashtables’ SOAP-for-rdf-query non spec that Libby Miller and I had implementations of. From the RDFAuthor tutorial:

The old Maryland BINPIQ SHOE knowledgebase query applet is the grandaddy of them all. Sadly I don’t have any screenshots and the applet itself seems to be coderotted. [...] Ah, but here I find an email I wrote about it 8 years ago(!), which has screenshots:

SemanticSoft from Moldova also have some visual SPARQL UI:

No real conclusion here. I just found myself looking around some of these links, and thought I’d share them. I’m sure there’s a lot more related work out there (eg. NIGHTLIGHT from folk at Southampton Uni), and that the rise of fancy HTML-based UIs and JSON for data access makes for an ever-more interesting environment for zero-install graphical query tools.

One thing I remember about the old Maryland applets: as their representational language became more expressive (moving from binary to n-ary), the graphical query UI became somewhat less intuitive. Now since SPARQL itself adds some concepts not in the underlying target language (ie. RDF doesn’t have named graphs, optionals etc), the ability to make a graphical query UI that exploits the “it’s just an RDF graph with bits labelled as missing” (per Guha’s original proposal) perhaps gets a bit strained. In particular, how might named graphs best be represented in visual editors?