Vadalog

Vadalog is a system for performing complex logic reasoning tasks over knowledge graphs.

[1] Vadalog was developed by researchers at the University of Oxford and Technische Universität Wien as well as employees at the Bank of Italy.

[7] The nature of knowledge graphs also makes the presence of recursion in these rules a particularly important aspect.

More technically, a program is recursive if the dependency graph built with the application of the rules is cyclical.

The Vadalog language allows to answer reasoning queries that also include recursion.

It is based on Warded Datalog±, which belongs to the Datalog± family of languages that extends Datalog with existential quantifiers in rule heads[9] and at the same time restricts its syntax in order to achieve decidability and tractability.

Although this is a limit in terms of expressive power, with this requirement and thanks to its architecture and termination algorithms, Warded Datalog± is able to find answers to a program in a finite number of steps.

[13] Vadalog replicates in its entirety Warded Datalog± and extends it with the inclusion in the language of: In addition, the system provides a highly engineered architecture to allow efficient computation.

The Vadalog system is therefore able to perform ontological reasoning tasks, as it belongs to the Datalog family.

Reasoning with the logical core of Vadalog captures OWL 2 QL and SPARQL[16] (through the use of existential quantifiers), and graph analytics (through support for recursion and aggregation).

Note the existential quantification in the first position of the ancestor predicate in the first rule, which will generate a null νi in the chase procedure.

The Vadalog system can be employed to address many real-world use cases from distinct research and industry fields.

This scenario consists in determining whether there exists a link between two entities in a company ownerships graph.

The third rule states that, if the sum of all the partial shares S of Y owned directly or indirectly by X is greater than or equal to 20% of the equity of Y, then they are close links according to the first definition.