A logic for specifying and reasoning about object classes and their instances (aspects) is presented and illustrated. This logic is an extension of a rather standard linear temporal, many-sorted, first-order predicate logic with equality. The extensions where designed to be as simple as possible while supporting the envisaged locality of arguments, object specialization and object aggregation. Objects are specified through their aspects. Each aspect establishes a local vocabulary (signature). The logic works at two levels: first, we can specify and prove assertions about a given object aspect in isolation (local reasoning), eg persons, or patients, or cars; second, we can specify interaction constraints and make inferences between aspects within the same community of objects (global reasoning), eg carry the theorems of persons onto patients (specialization inheritance), or carry the theorems of persons onto the aggregations of persons and cars (incorporation inheritance). Some reflecti...

The envisaged notion of object is presented as corresponding to the basic, universal building block of (information) systems. A simple mathematical model for fully concurrent objects (actors) is adopted that extends a suitable model for sequential processes. An object is defined as a process possibly endowed with initiative and tracedependent attributes. Transactional requirements are analysed within this framework as liveness requirements. Object aggregation is explained using the general notion of object morphism. The basic inheritance, overriding and reification mechanisms are also presented, as well as a suitable notion of object-type. The computational model is shown through examples to provide a sound basis for (information) systems design, including abstract conceptual modeling and layered implementation of both passive (record-like) and active (procedure-like) objects. The model establishes a suitable semantic domain for the envisaged broad spectrum specification/design languag...

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A brief overview is made of the use of temporal logic formalisms for specifying and verifying concurrent systems in general and information systems in particular. The requirements imposed by object-orientation on such formalisms are examined. A logic is proposed fulfilling those requirements (except concerning non-monotonic features), allowing the uniform treatment of both local and global properties of systems with concurrent, interacting components organized in classes, and supporting specialization. A semantics and a calculus (following an axiomatic, Hilbert style) are presented in detail. The calculus includes rules for the sound inheritance and reflection of theorems between classes. Practical aspects of the usage of such a logic for both specification and verification are considered. To this end a set of metatheorems is provided for expediting the proof of invariants. Finally, the need and availability of automatic theorem proving for systems querying is briefly discussed. Key wo...

From an arbitrary temporal logic institution we show how to set up the corresponding institution of objects. The main properties of the resulting institution are studied and used in establishing a categorial, denotational semantics of several basic constructs of object specification, namely aggregation (parallel composition), interconnection, abstraction (interfacing) and monotonic specialization. A duality is established between the category of theories and the category of objects, as a corollary of the Galois correspondence between these concrete categories. The special case of linear temporal logic is analysed in detail in order to show that categorial products do reflect interleaving and reducts may lead to internal nondeterminism. Key words: object-orientation, system specification, temporal logic, institution, denotational semantics, duality. 1 Introduction The advantages of object-orientation in software engineering in general and system specification in particular...

A simple linear propositional temporal logic is adopted for specifying object behaviour. It explicitly distinguishes action occurrence from action enabling. An institution for this logic is built and shown to provide a denotational categorial semantics to aggregation and hiding constructs. An operational domain of labelled transition systems with stuttering, extended with an acceptance condition based on the fulfilment of pending goals is proposed. Its relation to the semantic domain of the institution is exploited towards the achievement of an exact operational semantics, by summing up on the properties of the previously obtained denotational semantics. 1. Introduction The use of temporal logics 8;10 has been widely explored both on the fields of specification 12;15 and certification of properties 7;11;13 of reactive systems, namely of object-oriented systems 18;19;21 . The advantages are known to lie on the clear declarative formalization of the systems at hand and on the us...

In this paper we investigate concurrent actions and changes. We extend the standard situation calculus with concurrent actions and show that the extended situation calculus has the same expressive power as the original one. In the extended situation calculus we identify and focus on the composition problem which relates effects of concurrent actions to those of their component actions. A defeasible solution to the composition problem is proposed. The believability of some choices of default rules for the composition problem and atomicity of actions are discussed. We also provide some simple examples to illustrate the usefulness of our defeat rules. The result of this paper has been used in an abductive planner based on extended logic programs with explicit negation. 1 Introduction The situation calculus [11] is a very general framework for reasoning about actions and changes. Recent investigations have shown that the situation calculus is very useful in many AI applications such as pr...

A brief overview is made of the use of temporal logic formalisms for specifying and verifying concurrent systems in general and information systems in particular. The requirements imposed by object-orientation on such formalisms are examined. A logic is proposed fulfilling those requirements (except concerning non-monotonic features), allowing the uniform treatment of both local and global properties of systems with concurrent, interacting components organized in classes, and supporting specialization. A semantics and a calculus (following an axiomatic, Hilbert style) are presented in detail. The calculus includes rules for the sound inheritance and reflection of theorems between classes. Practical aspects of the usage of such a logic for both specification and verification are considered. To this end a set of metatheorems is provided for expediting the proof of invariants. Finally, the need and availability of automatic theorem proving for systems querying is briefly discussed. 1 Intr...

Requirements Engineering is more and more considered as a central phase in the development and implementation of computer systems. Within the context of CIM, the CIMOSA project proposes a set of models based on adequate concepts for expressing requirements. In this paper, we suggest how these models can be supported by the use of a fully formal requirements specification language called ALBERT and based on an agent-oriented real-time temporal logic framework.

We look into abductive reasoning in the context of propositional temporal object specification/verification. Our aim is to complete a given specification whenever some envisaged property does not hold. To this end we provide abductive techniques based on propositional tableaux and proof rules for the verification of temporal properties. The properties we are interested in are safety, guarantee, response and persistence properties. Explanations are enabling constraints and fairness requirements for actions. 1. Introduction Temporal logic is a widely accepted formalism for reactive system specification and verification, in general, and in object-oriented system specification and verification, in particular 12;18;5;19 . An object is a dynamic reactive entity with an internal state which is able to interact with other objects 17 . Following 19 , a temporal object signature is composed of a set of actions and a set of attributes. Attribute values reflect the object's internal state w...