Equational Characterization of Covariant-Contravariant Simulation and Conformance Simulation Semantics

Covariant-contravariant simulation and conformance simulation generalize plain simulation and try to capture the fact that it is not always the case that "the larger the number of behaviors, the better". We have previously studied their logical characterizations and in this paper we present the axiomatizations of the preorders defined by the new simulation relations and their induced equivalences. The interest of our results lies in the fact that the axiomatizations help us to know the new simulations better, understanding in particular the role of the contravariant characteristics and their interplay with the covariant ones; moreover, the axiomatizations provide us with a powerful tool to (algebraically) prove results of the corresponding semantics. But we also consider our results interesting from a metatheoretical point of view: the fact that the covariant-contravariant simulation equivalence is indeed ground axiomatizable when there is no action that exhibits both a covariant and a contravariant behaviour, but becomes non-axiomatizable whenever we have together actions of that kind and either covariant or contravariant actions, offers us a new subtle example of the narrow border separating axiomatizable and non-axiomatizable semantics. We expect that by studying these examples we will be able to develop a general theory separating axiomatizable and non-axiomatizable semantics.Comment: In Proceedings SOS 2010, arXiv:1008.190

Social Opportunity on Coffee Shop

Opportunities open a coffee shop in the mall and office buildings are still very open because for the city, drink coffee together has become a necessity. Everyone loved the coffee and coffee atmosphere relaxed, loose and information enjoyed while chatting, chat/browsing internet, small meeting or discussion. More than that the coffee shop has become a strategic place to make a deal and business negotiation or a place to spend time waiting for hours jammed in the capital. Café Republic (KKR) is the concept of specialty coffee bar espresso coffee made from ingredients of real coffee from various parts of Indonesia elected and diverse. KKR offer experience (experience) coffee with coffee bar atmosphere to enjoy a coffee ritual into something fun. This concept is made different from the coffee shop that currently exists in Indonesia

Structural Refinement for the Modal nu-Calculus

We introduce a new notion of structural refinement, a sound abstraction of logical implication, for the modal nu-calculus. Using new translations between the modal nu-calculus and disjunctive modal transition systems, we show that these two specification formalisms are structurally equivalent. Using our translations, we also transfer the structural operations of composition and quotient from disjunctive modal transition systems to the modal nu-calculus. This shows that the modal nu-calculus supports composition and decomposition of specifications.Comment: Accepted at ICTAC 201

Refinement checking on parametric modal transition systems

Modal transition systems (MTS) is a well-studied specification formalism of reactive systems supporting a step-wise refinement methodology. Despite its many advantages, the formalism as well as its currently known extensions are incapable of expressing some practically needed aspects in the refinement process like exclusive, conditional and persistent choices. We introduce a new model called parametric modal transition systems (PMTS) together with a general modal refinement notion that overcomes many of the limitations. We investigate the computational complexity of modal and thorough refinement checking on PMTS and its subclasses and provide a direct encoding of the modal refinement problem into quantified Boolean formulae, allowing us to employ state-of-the-art QBF solvers for modal refinement checking. The experiments we report on show that the feasibility of refinement checking is more influenced by the degree of nondeterminism rather than by the syntactic restrictions on the types of formulae allowed in the description of the PMTS

On Refinements of Boolean and Parametric Modal Transition Systems

We consider the extensions of modal transition systems (MTS), namely Boolean MTS and parametric MTS and we investigate the refinement problems over both classes. Firstly, we reduce the problem of modal refinement over both classes to a problem solvable by a QBF solver and provide experimental results showing our technique scales well. Secondly, we extend the algorithm for thorough refinement of MTS providing better complexity then via reductions to previously studied problems. Finally, we investigate the relationship between modal and thorough refinement on the two classes and show how the thorough refinement can be approximated by the modal refinement

Compositionality for Quantitative Specifications

We provide a framework for compositional and iterative design and verification of systems with quantitative information, such as rewards, time or energy. It is based on disjunctive modal transition systems where we allow actions to bear various types of quantitative information. Throughout the design process the actions can be further refined and the information made more precise. We show how to compute the results of standard operations on the systems, including the quotient (residual), which has not been previously considered for quantitative non-deterministic systems. Our quantitative framework has close connections to the modal nu-calculus and is compositional with respect to general notions of distances between systems and the standard operations

Improvement and Analysis of behavioural models with variability

Product Lines or Families represent a new paradigm widely used to describe company products with similar functionality and requirements in order to improve efficiency and productivity of a company. In this context many studies are focused on the research of the best behavioural model useful to describe a product family and to reason about properties of the family itself. In addition the model must allow to describe in a simple way different types of variability, needed to characterize several products of the family. One of the most important of these models is the Modal Transition System (MTS), an extension of a Labelled Transition System (LTS), which introduces two types of transitions useful to describe the necessary and allowed requirements. These models have been broadly studied and several its extensions have been described. These extensions follow different approaches which entail the introduction of more and more complex and expressive requirements. Furthermore MTS and its extensions define a concept of refinement which represents a step of design process, namely a step where some allowed requirements are discarded and other ones become necessary. In this thesis we introduce a new model, the Constrained Modal Transition System (CMTS ), which is a particular and more expressive extension of MTS. Moreover we study different and useful properties correlated to the CMTS. Also, we use CMTS as an useful tool to determine and to define a a hierarchy of expressivity of the known extensions with variability of LTSs and MTSs. In order to check different properties of a product family, we introduce a new deontic-temporal logic based on CTL* interpreted over CMTSs able to express classical safety and liveness properties as well as concepts like obligatory, permission and prohibition. Finally some useful optimizations are introduced to guarantee a less expensive verification from complexity point of view

<strong>On Determinism in Modal Transition Systems</strong>

AbstractModal transition system (MTS) is a formalism which extends the classical notion of labelled transition systems by introducing transitions of two types: must transitions that have to be present in any implementation of the MTS and may transitions that are allowed but not required.The MTS framework has proved to be useful as a specification formalism of component-based systems as it supports compositional verification and stepwise refinement. Nevertheless, there are some limitations of the theory, namely that the naturally defined notions of modal refinement and modal composition are incomplete with respect to the semantic view based on the sets of the implementations of a given MTS specification. Recent work indicates that some of these limitations might be overcome by considering deterministic systems, which seem to be more manageable but still interesting for several application areas.In the present article, we provide a comprehensive account of the MTS framework in the deterministic setting. We study a number of problems previously considered on MTS and point out to what extend we can expect better results under the restriction of determinism