ProGS: Property Graph Shapes Language

Seifer, Philipp, Lämmel, Ralf and Staab, Steffen (2021) ProGS: Property Graph Shapes Language. 20th International Semantic Web Conference, Virtual Event. 24 - 28 Oct 2021. 17 pp . (In Press)

Record type: Conference or Workshop Item (Paper)

Abstract

Knowledge graphs such asWikidata are created by a diversity of contributors
and a range of sources leaving them prone to two types of errors. The
first type of error, falsity of facts, is addressed by property graphs through the
representation of provenance and validity, making triples occur as first-order objects in subject position of metadata triples. The second type of error, violation of domain constraints, has not been addressed with regard to property graphs so far. In RDF representations, this error can be addressed by shape languages such as SHACL or ShEx, which allow for checking whether graphs are valid with respect
to a set of domain constraints. Borrowing ideas from the syntax and semantics
definitions of SHACL, we design a shape language for property graphs, ProGS,
which allows for formulating shape constraints on property graphs including their
specific constructs, such as edges with identities and key-value annotations to
both nodes and edges. We define a formal semantics of ProGS, investigate the
resulting complexity of validating property graphs against sets of ProGS shapes,
compare with corresponding results for SHACL, and implement a prototypical
validator that utilizes answer set programming.