Turku Centre for Computer Science

About: Turku Centre for Computer Science is a facility organization based out in Turku, Finland. It is known for research contribution in the topics: Decidability & Word (group theory). The organization has 382 authors who have published 1027 publications receiving 19560 citations.

Formalising UML state machines for model checking

Abstract: The paper discusses a complete formalisation of UML state machine semantics. This formalisation is given in terms of an operational semantics and it can be used as the basis for code-generation, simulation and verification tools for UML Statecharts diagrams. The formalisation is done in two steps. First, the structure of a UML state machine is translated into a term rewriting system. In the second step, the operational semantics of state machines is defined. In addition, some problematic situations that may arise are discussed. Our formalisation is able to deal with all the features of UML state machines and it has been implemented in the vUML tool, a tool for model-checking UML models.

A Study of The Fragile Base Class Problem

Abstract: In this paper we study the fragile base class problem. This problem occurs in open object-oriented systems employing code inheritance as an implementation reuse mechanism. System developers unaware of extensions to the system developed by its users may produce a seemingly acceptable revision of a base class which may damage its extensions. The fragile base class problem becomes apparent during maintenance of open object-oriented systems, but requires consideration during design. We express the fragile base class problem in terms of a flexibility property. By means of five orthogonal examples, violating the flexibility property, we demonstrate different aspects of the problem. We formulate requirements for disciplining inheritance, and extend the refinement calculus to accommodate for classes, objects, class-based inheritance, and class refinement. We formulate and formally prove a flexibility theorem demonstrating that the restrictions we impose on inheritance are sufficient to permit safe substitution of a base class with its revision in presence of extension classes.

A survey on ontologies for human behavior recognition

Abstract: Describing user activity plays an essential role in ambient intelligence. In this work, we review different methods for human activity recognition, classified as data-driven and knowledge-based techniques. We focus on context ontologies whose ultimate goal is the tracking of human behavior. After studying upper and domain ontologies, both useful for human activity representation and inference, we establish an evaluation criterion to assess the suitability of the different candidate ontologies for this purpose. As a result, any missing features, which are relevant for modeling daily human behaviors, are identified as future challenges.