SPIN: SPARQL Inferencing Notation
From the webpage:
SPIN is a W3C Member Submission that has become the de-facto industry standard to represent SPARQL rules and constraints on Semantic Web models. SPIN also provides meta-modeling capabilities that allow users to define their own SPARQL functions and query templates. Finally, SPIN includes a ready to use library of common functions.
In case you encounter SPARQL rules and constraints.
I first saw this in a tweet by Stian Danenbarger.