4 papers
Provenance for Regular Path Queries
Gosta Grahne, Alex Thomo
Regular path queries (RPQs) the ubiquitous mechanism for querying data graphs of partially known structure. RPQs are in essence regular expressions over the edge symbols. The answe…
Universal (and Existential) Nulls
Gösta Grahne, Ali Moallemi
Incomplete Information research is quite mature when it comes to so called {\em existential nulls}, where an existential null is a value stored in the database, representing an unk…
Conditional Tables in practice
Gosta Grahne, Adrian Onet, Nihat Tartal
Due to the ever increasing importance of the internet, interoperability of heterogeneous data sources is as well of ever increasing importance. Interoperability can be achieved e.g…
Anatomy of the chase
Gosta Grahne, Adrian Onet
A lot of research activity has recently taken place around the chase procedure, due to its usefulness in data integration, data exchange, query optimization, peer data exchange and…