41 research outputs found
Semantics and Validation of Shapes Schemas for RDF
We present a formal semantics and proof of soundness for shapes schemas, an
expressive schema language for RDF graphs that is the foundation of Shape
Expressions Language 2.0. It can be used to describe the vocabulary and the
structure of an RDF graph, and to constrain the admissible properties and
values for nodes in that graph. The language defines a typing mechanism called
shapes against which nodes of the graph can be checked. It includes an
algebraic grouping operator, a choice operator and cardinality constraints for
the number of allowed occurrences of a property. Shapes can be combined using
Boolean operators, and can use possibly recursive references to other shapes.
We describe the syntax of the language and define its semantics. The
semantics is proven to be well-defined for schemas that satisfy a reasonable
syntactic restriction, namely stratified use of negation and recursion. We
present two algorithms for the validation of an RDF graph against a shapes
schema. The first algorithm is a direct implementation of the semantics,
whereas the second is a non-trivial improvement. We also briefly give
implementation guidelines
Semi Automatic Construction of ShEx and SHACL Schemas
We present a method for the construction of SHACL or ShEx constraints for an existing RDF dataset. It has two components that are used conjointly: an algorithm for automatic schema construction, and an interactive workflow for editing the schema. The schema construction algorithm takes as input sets of sample nodes and constructs a shape constraint for every sample set. It can be parametrized by a schema pattern that defines structural requirements for the schema to be constructed. Schema patterns are also used to feed the algorithm with relevant information about the dataset coming from a domain expert or from some ontology. The interactive workflow provides useful information about the dataset, shows validation results w.r.t. the schema under construction, and offers schema editing operations that combined with the schema construction algorithm allow to build a complex ShEx or SHACL schema
Shape Designer for ShEx and SHACL Constraints
International audienceWe present Shape Designer, a graphical tool for building SHACL or ShEx constraints for an existing RDF dataset. Shape Designer allows to automatically extract complex constraints that are satisfied by the data. Its integrated shape editor and validator allow expert users to combine and modify these constraints in order to build an arbitrarily complex ShEx or SHACL schema