International audience

Nowadays, architects are facing the challenge of proliferation of stakeholder requirements for preserving and ensuring the effectiveness of the software, by using software evolution as a key solution. Hence, in terms of landscaping evolution space there is a great need to define the thinking on which efforts to deal with this issue have been based. In this paper, we propose a framework for software architecture evolution taxonomy based on four structural dimensions. This framework could both position existing evolution models in the field and highlight gray areas for the future. Mapping over framework dimensions, a set of quality factors and an investigation including 67 studies are performed to assess the proposals. The results contain a number of relevant findings, including the need to improve software architecture evolution by accommodating predictable changes as well as promoting the emergence of operating mechanisms.

Service Oriented Architecture (SOA) is a paradigm that provides important properties for the development of business applications like flexibility and loose coupling. In our research work, we focus on the use of SOA to implement specific architectures of inter-organizational workflows (IOWF). The current paper deals with the “Loosely Coupled Workflow” specifying an IOWF-architecture that connects two or more workflows - attached to a set of business partners-communicating in an asynchronous manner according to a public communication protocol conjointly defined by all partners. The first issue of this work is to define a service based cooperation pattern called LC-IOWF pattern suitable to the architecture considered in order to obtain IOWF models flexible enough to ease their adaptation. The proposed LC-IOWF pattern is based on three main dimensions: services, control of execution and interactions. Then, we define three categories of adaptation patterns corresponding to the three dimensions exhibited. Particularly, the third category of these patterns called “Interaction adaptation patterns” concerns adaptations affecting the communication protocol and constitutes a specific type of adaptation compared with other IOWF-architectures. For implementation, we consider IOWF models specified with BPEL.

Views and abstraction levels are two major concepts introduced in the software engineering domain in order to enhance the architectural organization of complex systems' requirements. Despite numerous and substantial works that built and refined those concepts, they still less secure and less standardized to be part of a rough software architecture. This paper begins with a survey of evolution of the role and usage of those concepts in software architecture, and ends with an overview of an approach integrating the views and abstraction levels concepts within a single rough multi-views/multi-abstraction levels software architecture and respecting their usage in an evolutionary architectural specification analysis. The main benefits of this contribution was to allow system architects to solve more efficiently the complexity problems; and allow them to build a complex, organized and coherent architecture; and finally enhance the communication and harmony among different stakeholders.

The SOA (Service Oriented Architecture) paradigm provides important advantages like interoperability, reusability and flexibility required in the area of business applications. In our research works, we focus on the use of SOA to implement inter-organizational workflows (IOWF). Our goal is to obtain IOWF models flexible enough in order to ease their adaptation at build-time and at runtime, because services are loosely coupled components, easily invoked and interoperable. This paper focuses on specific and well common IOWF-architectures defined in the literature; it deals with adaptation of IOWF process models obeying to these architectures. First, we define the concept of Service-Based Cooperation Pattern (SBCP) that supports service-based IOWF models meeting one of the specific architectures considered. Then, we state a set of recurrent operations of adaptation (attached to process and interaction aspects) that can be applied on service-based IOWF models, and we illustrate their implementation for IOWF models specified with BPEL.

SPEM is a metamodel adopted by the OMG for software processes engineering. For the software process architectures description, SPEM architectural concepts are very insufficient. Indeed, the existing concepts disallow describing configurations and explicit links specific to software process architectures and finally their deployment. The objective of this paper is to present an extension of SPEM (System and Software Process Engineering Metamodel) with lacking architectural concepts. This extension is an important step to implement a new approach for software process reusing based on software architectures.

As software systems grow, their complexity augments rapidly. In consequence their understandability and evolvability are becoming a difficult task. To address this issue, we have previously defined COSA (Component-Object based Software Architecture), which is a software architecture model that describes systems as a collection of components and connectors. However, COSA has been undertaken with academic rather than commercial goals. This paper presents a modeling tool (called COSABuilder) and instantiating tool (called COSAInstantiator) for COSA metamodel and describes their various features. Our contribution is not only offering MDA-based tools but also automatic instantiation and automatic verification of software architecture specifications. The goal is to preserve architecture traceability features in the modeling space and to create accurate architectures.

Despite that reuse libraries are now well adopted during software development step, software evolution step is not yet covered by this kind of beneficial approach. In this paper we present the "evolution shelf", a generic infrastructure to achieve for-reuse and by-reuse techniques within the field of software evolution. The basic idea behind that is to propose and encourage the reuse of recurring and reliable evolution expertises to achieve the structural evolution of a software system at the architectural level. For that purpose, the shelf assists architects in classifying, storing and selecting reusable architectural evolution operations. The underlying concept that we propose to capitalize the expertises is called "evolution style" and it mixes a syntactic and a semantic description format. These ideas form a core for a long-term vision in which it is possible to build a business model of evolution-of-the-shelf (EOTS) with the special objective to decrease the efforts and the risks related to the evolution activities.

Software architecture modeling and representation became a main phase of the development process of complex systems. In fact, software architecture representation provides many advantages during all phases of software life cycle. Nevertheless, for many systems, like legacy or eroded ones, there is no available representation of their architectures. In order to benefit from this representation, we propose, in this paper, an approach called ROMANTIC which focuses on extracting a component-based architecture of an existing object-oriented system. The main idea of this approach is to propose a quasi-automatic process of architecture recovery based on semantic and structural characteristics of software architecture concepts.

In this article we show how knowledge representation techniques can be applied to software architecture. We define a representation model for software architecture concepts. The model is based on MY model (meta modeling in Y), which is a knowledge engineering methodology. It represents software architecture concepts using three branches: component, connector, and architecture. The component branch represents concepts that are related to computations, the connector branch represents concepts that are related to interactions, and the architecture branch represents concepts that are related to the structure and the topology of the system described. We think that such a representation of architecture concepts aids in improving reusability not only at the implementation level, but also at the description level. The model assigns a hierarchical library for the four software architecture conceptual levels (meta-meta architecture level, meta architecture level, architecture level, application level).

Adapting software components to be used in a particular application is a crucial issue in software component-based technology. In fact, software components can be used in contexts with characteristics different from those envisaged when designing the component. To deal with this issue, we propose in this paper an approach aiming at adapting a software component structure in order to preserve service continuity. This adaptation, achieved by component fragmentation, allows its structure reconfiguration and its redeployment while preserving its behavior and its services. The structural adaptation process is based on two phases. The first one consists of the component re-engineering in order to introduce runtime adaptation facilities. The second phase, achieved since runtime, aims at reconfiguring the component structure according to the user needs.

This paper presents our work on component-based software evolution. More precisely, we highlight how connectors enhance component-based software architecture evolution. Indeed, connectors, by their intermediary's position between components, can play an important role for automating the propagation of evolution impacts, while preserving the architecture coherence. For that, we outline connectors' characteristics that we consider as principal for aims of evolution management. We validate and exploit these characteristics on our evolution model SAEV (software architecture evolution model). To achieve this, we need to enrich the concept of connector with information about the degree of correlation and of dependency existing between components. For that, we propose to characterize the connector concept with semantic properties, namely: exclusivity/sharing, dependency/ independency, predominance/non predominance, cardinality and reverse cardinality.

As the concept of meta-classes was introduced in order to permit the manipulation of classes, we introduce the concept of meta-components, meta-connectors, and meta-architectures to permit the manipulation and the redefinition of architectural elements (structural and behavioral). In this article we present a meta-meta-architecture called MADL (Meta Architecture Description Language) to abstract the notions of architectures (components, connectors, architectures), hence to facilitate their manipulation, reuse, and evolution; and also to ease (hence encourage) the transformation and comparison among ADLs.

In this paper we contribute to the issue of integrating architectural description notations into OMG based modeling techniques using a meta ADL.. The outcome of this work is a meta ADL that helps in approaching issues such as mapping, comparing, and unifying ADLs.

In this paper, we propose a modeling technique which permits to describe a KBS (Knowledge Based Systems) architecture according to two CBS (Components Based Systems) axis : the components architecture axis and the levels of granularity of components axis. The components architecture axis allows to see a KBS as a set of inter-related components for reuse purposes. The levels of granularity of components axis allows to describe the KBS components according to different levels of granularity for clarity and reuse purposes.

Query formulation remains obstinately difficult for large classes of users. Indeed, with the exception of approaches facilitating syntax problems, there is a noticeable absence of models taking charge of the user through from specification of their needs to formulation of their queries. In this article, we take a novel look to object-oriented queries — reifying the ones which users formulate as components then reusing them, by means of strategies for selecting, assembling and adapting them to help in the formulation of new complex queries.

Query formulation remains obstinately difficult for large classes of users. Indeed, in face of the growth in query complexity due to development of new kind of application manipulating great size of data, we notice the absence of models taking charge of the user through from specification of needs to formulation of queries. We think that users can be given effective help in query formulation by means of re-using former queries. Indeed, the objective of this work is to propose a method of assisting users to formulate queries by accessing and re-using existing ones. It consists of making available to users query components plus a strategy for re-using them. The approach developed here lies within the scope of re-use development environments. The model developed incorporates knowledge defining query components and ways to select, adapt or combine them to meet particular requirements.

In database or knowledge-base systems, query formulation languages are the means offered to users for accessing data or knowledge. Queries allow selection of data under particular, either simple or complex constraints, resulting from one or several structures. However, query formulation remains obstinately difficult for large classes of users. Indeed, with the exception of approaches facilitating syntax problems, there is a noticeable absence of models taking charge of the user through specification of their needs to formulation of their queries. In the case of object-oriented database systems, whose data models and concepts are more complex than those of relational databases, database users need assistance with several kinds of formulation problems. In this respect, we consider that the storage and reuse of former queries constitutes a promising avenue of investigation. We take a novel look at object-oriented queries, reifying the ones which users formulate as components then reusing them, by means of strategies for selecting, assembling and adapting them to help in the formulation of new complex queries.

Database applications which model aspects of the real world should be able to express as accurately as possible the different nuances of reality; that includes the need to evolve internally in response to signals of updates coming from the environment. These updates are not always supplied in an ideal and complete manner and are not always predefined or precisely defined. In practice, requirements for evolution generally occur during the manipulation of objects while running the database. It is frequently necessary to change individual objects, less frequently the database schema. Database systems need to have mechanisms capable, whenever and as well as possible, of assimilating this new information correctly and diagnosing and implementing the changes necessary.

We propose an approach facilitating query formulation for users sharing a common database. Our approach is based on two considerations. On the one hand, query formulation can be considered as a skill which can be shared entirely or partly between users. Accordingly we propose a model for storing and making available this skill to help users formulate their new queries. On the other hand we base our design on custom construction of a database adapted to each business group of users in question. In using it, the users of a given business cooperate transparently through their queries to design databases specific to their business. Thus, they take part co-operatively if indirectly in reducing the difficulty of query formulation.

This paper presents the CHIC (Constraints in Hierarchical Composite objects) model for expressing and maintaining constraints between objects in a part-whole hierarchy.This model is based essentially on the semantics of the part-whole relation both in representing and managing constraints.Its principal contribution involves integrating an explicit object-oriented constraint model in complex objects with contextual reactivity.

Multiple inheritance systems with exceptions in object-oriented languages are examined. Two types of exceptions may be identified: exceptions by cancellation of an inheritance link and exceptions by cancellation of property. For each type of exception, contradictions appear when there are simultaneously several paths of the inheritance graph, which allow inheritance from an object or from a property to take place or not. If certain contradictions are commonly solved by masking, there are contradictions for which no common method of resolution exists. A method for the management of the contradictions in object languages is proposed. This method is based on a computation of the complexity of inheritance paths which produce a contradiction.>