Petra Selmer

Birkbeck, University of London · Department of Computer Science and Information Systems

As graph databases become widespread, JTC1 -- the committee in joint charge of information technology standards for the International Organization for Standardization (ISO), and International Electrotechnical Commission (IEC) -- has approved a project to create GQL, a standard property graph query language. This complements a project to extend SQL...

The scientific community has been studying graph data models for decades. Their high expressiveness and elasticity led the scientific community to design a variety of graph data models and graph query languages, and the practitioners to use them to model real-world cases and extract useful information. Recently, property graphs and, in particular,...

Ensuring the success of big graph processing for the next decade and beyond.

Graphs are by nature unifying abstractions that can leverage interconnectedness to represent, explore, predict, and explain real- and digital-world phenomena. Although real users and consumers of graph instances and graph workloads understand these abstractions, future problems will require new abstractions and systems. What needs to happen in the...

The paper describes the present and the future of graph updates in Cypher, the language of the Neo4j property graph database and several other products. Update features include those with clear analogs in relational databases, as well as those that do not correspond to any relational operators. Moreover, unlike SQL, Cypher updates can be arbitraril...

The Cypher property graph query language is an evolving language, originally designed and implemented as part of the Neo4j graph database, and it is currently used by several commercial database products and researchers. We describe Cypher 9, which is the first version of the language governed by the openCypher Implementers Group. We first introduc...

Given the heterogeneity of complex graph data on the web, such as RDF linked data, it is likely that a user wishing to query such data will lack full knowledge of the structure of the data and of its irregularities. Hence, providing flexible querying capabilities that assist users in formulating their information seeking requirements is highly desi...

Given the heterogeneity of complex graph data on the web, such as RDF linked data,a user wishing to query such data may lack full knowledge of its structure and irregularities. Hence, providing users with flexible querying capabilities can be beneficial. The query language we adopt comprises conjunctions of regular path queries, thus including exte...

This paper discusses the provision of flexible querying facilities over heterogeneous data arising from lifelong learners' educational and work experiences. A key aim of such querying facilities is to allow learners to identify possible choices for their future learning and professional development by seeing what others have done. We motivate and d...

We present a formal framework for (minimal) mod- ule extraction based on an abstract notion of in- separability w.r.t. a signature between ontologies. Two instances of this framework are discussed in detail for DL-Lite ontologies: concept inseparabil- ity, when ontologies imply the same complex con- cept inclusions over the signature, and query in-...

This paper considers the concurrent use of both query ap-proximation and query relaxation within one integrated 'flex' operation that can be applied to regular path queries over complex, heterogeneous graph data, such as RDF linked data, in order to support flexible querying of such data. We describe the semantics and implementation of our 'flex' o...