Query language constructs for provenance

Provenance that records the derivation history of data is useful for a wide variety of applications, including those where an audit trail needs to be provided, where the sources and the trust-level attributed to the sources contribute to determining the trust-level in results etc. There have been different efforts in the past for representing provenance information, the most notable being the Open Provenance Model (OPM). OPM defines structures for representing the provenance information as a graph with nodes and edges, and also specifies inference queries. Our work builds on these by proposing query language constructs, that the users will find useful for manipulating the provenance information. Rather than specifying a query language, we define two classes of algebraic constructs: content-based operators that operate on the content of nodes and edges, and structure-based operators that operate on the graph structure of the provenance graph. These content-based and the structure-based constructs can be combined to express a wide variety of interesting queries on the provenance data that go much beyond simple inference queries as expressible using Datalog/SQL.