The SPARQL Rules language SPIN has evolved over the last couple of years as an integral part of TopQuadrant's TopBraid Suite. SPIN started during a discussion between Dean Allemang and myself, in which we brainstormed about having an RDF syntax for SPARQL. I went ahead and implemented this based on Jena's ARQ API, and the result eventually became the SPIN RDF Syntax. This was no rocket science, because similar ideas of representing higher level languages by means of RDF blank node structures had been explored by OWL and SWRL.
SPIN is a W3C Member Submission
Prior to our work on SPIN, we had already experimented with various mechanisms to link SPARQL queries with RDF data structures, so that they could be shared as query libraries. TopBraid veterans may remember the sparql:query property that was introduced to store SPARQL queries (as strings) together with RDF models. So while I was working on the SPIN RDF Syntax, I noticed that we now have a much better way of achieving this goal. A quick cross-reference to object-oriented languages led to me select properties such as spin:rule and spin:constraint to point from a class to a SPARQL query, expressed in RDF. This later became the SPIN Modeling Vocabulary.
Once I had the rules and constraint mechanism in place, I noticed that many rules and constraints were following similar patterns, with just one or two values different in each rule. This led to the creation of SPIN Templates. Templates then became the foundation of user-defined SPIN Functions. With those two pieces in place, SPIN suddenly became a language that was fundamentally different (and better) than what similar languages such as SWRL provided, because it became possible for users to define their own modeling vocabulary, and even extend the expressivity of SPARQL.
The first version of SPIN was published as part of TopBraid Composer in January 2009. Since then, it was positively received by our user community and practical use cases have enabled us to fine tune and extend the language over the years. Now, around three years after its first experimental versions, we found the time was right to officially share SPIN with the broader community, and make clear that it is not a proprietary TopQuadrant technology. Together with James Hendler and Kingsley Idehen, we put together a SPIN W3C Member Submission that has just been published on the W3C site.
The status of a Member Submission means that TopQuadrant encourages other tool vendors to also provide SPIN implementations, and as I have heard there is work in progress already. The Member Submission also indicates that SPIN may play a role as input to future revisions of other standards such as RIF. This is all very good. Of course a full spec of SPIN as an official W3C standard would be even better, but going through the whole standardization process is a long and difficult journey. Given that SWRL had become a similar de-facto standard with Member Submission status alone indicates to me that SPIN has good chances of achieving the same. In fact I strongly believe that the fact that SPIN is based on SPARQL will be crucial in winning the hearts and minds of many Semantic Web and Linked Data enthusiasts. SPIN can co-exist with other languages including OWL 2 RL and SKOS. SPIN doesn't require any special execution engine apart from a SPARQL store. The learning curve is very low for anyone who already knows SPARQL. SPIN is part of the Semantic Web technology stack.