Checking semantics in UML models: use cases diagrams

Constraints add to the semantics to UML models in the form of statements which are expected to hold for the model to be considered correct, i.e., to satisfy system requirements. Constraints are considered in the UML metamodel as adornments attached to model elements, and languages like OCL allow for different statements to be expressed. Despite several CASE-like tools are currently supporting UML diagram and constraint definition, as far as we know none of them provides support for verification and maintainance of constraint consistency. Having this kind of facility helps users in the design of UML models, specially when these models are complex and the impact of model evolution is difficult to trace. This work studies how constraint consistency may be compromised when model elements are introduced or modified during system development. Focus is over use case diagrams, which suffice to highlight a number of important issues related with consistency maintenance. We introduce procedures for verifying and maintaining constraint consistency, and illustrate them using a simple constraint specification language. Our goal is to make a first step in the development of tools for automatic verification and mantainance of model semantics.Eje: Ingeniería de softwareRed de Universidades con Carreras en Informática (RedUNCI

Explanations and Proof Trees

This paper proposes a model for explanations in a set theoretical framework using the notions of closure or fixpoint. In this approach, sets of rules associated with monotonic operators allow to define proof trees. The proof trees may be considered as a declarative view of the trace of a computation. We claim they are explanations of the results of a computation. This notion of explanation is applied to constraint logic programming, and it is used for declarative error diagnosis. It is also applied to constraint programming, and used for constraint retraction

Checking semantics in UML models: use cases diagrams

Constraints add to the semantics to UML models in the form of statements which are expected to hold for the model to be considered correct, i.e., to satisfy system requirements. Constraints are considered in the UML metamodel as adornments attached to model elements, and languages like OCL allow for different statements to be expressed. Despite several CASE-like tools are currently supporting UML diagram and constraint definition, as far as we know none of them provides support for verification and maintainance of constraint consistency. Having this kind of facility helps users in the design of UML models, specially when these models are complex and the impact of model evolution is difficult to trace. This work studies how constraint consistency may be compromised when model elements are introduced or modified during system development. Focus is over use case diagrams, which suffice to highlight a number of important issues related with consistency maintenance. We introduce procedures for verifying and maintaining constraint consistency, and illustrate them using a simple constraint specification language. Our goal is to make a first step in the development of tools for automatic verification and mantainance of model semantics.Eje: Ingeniería de softwareRed de Universidades con Carreras en Informática (RedUNCI

Constraint Retraction in CLP(FD): Formal Framework and Performance Results

. Constraint retraction can be described, in general, as the possibility of deleting a previously stated piece of information. This is obviously very convenient in many programming frameworks, especially in those that involve some level of interaction between the user and the system, or also in those concerning rescheduling or replanning. Nevertheless, constraint retraction is usually not provided in current constraint programming environments. This is mainly due to its high complexity and also to its non-monotonic nature, which would make most of such systems much more complex to reason with. In this paper we avoid these problems by considering a specific constraint programming framework, called clp(FD), that is, constraint logic programming (CLP) over finite domain (FD) constraints. We propose an algorithm which deletes a constraint from a set of FD constraints, while maintaining partial arc-consistency, which is usual in this programming framework. What is crucial is that the retra..