Underspecification, Inherent Nondeterminism and Probability in Sequence Diagrams

Abstract. Nondeterminism in specifications may be used for at least two different purposes. One is to express underspecification, which means that the specifier for the same environment behavior allows several alterna-tive behaviors of the specified component and leaves the choice between these to those responsible for implementing the specification. In this case a valid implementation will need to implement at least one, but not nec-essarily all, alternatives. The other purpose is to express inherent nonde-terminism, which means that a valid implementation needs to reflect all alternatives. STAIRS is an approach to the compositional and incremental development of sequence diagrams supporting underspecification as well as inherent nondeterminism. Probabilistic STAIRS builds on STAIRS and allows probabilities to be included in the specifications. Underspecifica-tion with respect to probabilities is also allowed. This paper investigates the use of underspecification, inherent nondeterminism and probability in sequence diagrams, the relationships between these concepts, and how these are expressed in STAIRS and probabilistic STAIRS.

Evolution of the UML Interactions Metamodel

UML Interactions represent one of the three different behavior kinds of the UML. In general, they specify the exchange of messages among parts of a system. Although UML Interactions can reside on different level of abstractions, they seem to be sufficiently elaborated for a higher-level of abstraction where they are used for sketching the communication among parts. Its metamodel reveals some fuzziness and imprecision where definitions should be accurate and concise, though. In this paper, we propose improvements to the UML Interactions’ metamodel for Message arguments and Loop CombinedFragments that make them more versatile. We will justify the needs for the improvements by precisely showing the shortcomings of the related parts of the metamodel. We demonstrate the expressiveness of the improvements by applying them to examples that current Interactions definition handles awkwardlyacceptedVersio

A denotational model for component-based risk analysis

Risk analysis is an important tool for developers to establish the appropriate protection level of a system. Unfortunately, the shifting environment of components and component-based systems is not adequately addressed by traditional risk analysis methods. This report addresses this problem from a theoretical perspective by proposing a denotational model for component-based risk analysis. In order to model the probabilistic aspect of risk, we represent the behaviour of a component by a probability distribution over communication histories. The overall goal is to provide a theoretical foundation facilitating an improved understanding of risk in relation to components and component-based system development