Ontology-based end-user visual query formulation: Why, what, who, how, and which?

Value creation in an organisation is a time-sensitive and data-intensive process, yet it is often delayed and bounded by the reliance on IT experts extracting data for domain experts. Hence, there is a need for providing people who are not professional developers with the flexibility to pose relatively complex and ad hoc queries in an easy and intuitive way. In this respect, visual methods for query formulation undertake the challenge of making querying independent of users’ technical skills and the knowledge of the underlying textual query language and the structure of data. An ontology is more promising than the logical schema of the underlying data for guiding users in formulating queries, since it provides a richer vocabulary closer to the users’ understanding. However, on the one hand, today the most of world’s enterprise data reside in relational databases rather than triple stores, and on the other, visual query formulation has become more compelling due to ever-increasing data size and complexity—known as Big Data. This article presents and argues for ontology-based visual query formulation for end-users; discusses its feasibility in terms of ontology-based data access, which virtualises legacy relational databases as RDF, and the dimensions of Big Data; presents key conceptual aspects and dimensions, challenges, and requirements; and reviews, categorises, and discusses notable approaches and systems

Contracts for Multi-instance UML Activities

International audienceWe present a novel way of encapsulating UML activities using interface contracts, which allows to verify functional properties that depend on the synchronization of parallel instances of software components. Encapsulated UML activities can be reused together with their verification results in SPACE, a model-driven engineering method for reactive systems. Such compositional verification significantly improves the scalability of the method. Employing a small example of a load balancing system, we explain the semantics of the contracts using the temporal logic TLA. Thereafter, we propose a more easily comprehensible graphical notation and clarify that the contracts are able to express the variants of multiplicity that we can encounter using UML activities. Finally, we give the results of verifying some properties of the example system using the TLC model checker