Lorenzo Bettini

Delta-oriented programming of software product lines

Feature-oriented programming (FOP) implements software product lines by composition of feature modules. It relies on the principles of stepwise development. Feature modules are intended to refer to exactly one product feature and can only extend existing implementations. To provide more flexibility for implementing software product lines, we propose delta-oriented programming (DOP) as a novel programming language approach. A product line is represented by a core module and a set of delta modules. The core module provides an implementation of a valid product that can be developed with well-established single application engineering techniques. Delta modules specify changes to be applied to the core module to implement further products by adding, modifying and removing code. Application conditions attached to delta modules allow handling combinations of features explicitly. A product implementation for a particular feature configuration is generated by applying incrementally all delta modules with valid application condition to the core module. In order to evaluate the potential of DOP, we compare it to FOP, both conceptually and empirically.

Global Progress in Dynamically Interleaved Multiparty Sessions

A multiparty session forms a unit of structured interactions among many participants which follow a prescribed scenario specified as a global type signature. This paper develops, besides a more traditional communicationtype system, a novel static interactiontype system for global progress in dynamically interleaved multiparty sessions.

Software diversity: state of the art and perspectives

Diversity is prevalent in modern software systems to facilitate adapting the software to customer requirements or the execution environment. Diversity has an impact on all phases of the software development process. Appropriate means and organizational structures are required to deal with the additional complexity introduced by software variability. This introductory article to the special section “Software Diversity—Modeling, Analysis and Evolution” provides an overview of the current state of the art in diverse systems development and discusses challenges and potential solutions. The article covers requirements analysis, design, implementation, verification and validation, maintenance and evolution as well as organizational aspects. It also provides an overview of the articles which are part of this special section and addresses particular issues of diverse systems development.

The Klaim Project: Theory and Practice

Klaim (Kernel Language for Agents Interaction and Mobility) is an experimental language specifically designed to program distributed systems consisting of several mobile components that interact through multiple distributed tuple spaces. Klaim primitives allow programmers to distribute and retrieve data and processes to and from the nodes of a net. Moreover, localities are first-class citizens that can be dynamically created and communicated over the network. Components, both stationary and mobile, can explicitly refer and control the spatial structures of the network. This paper reports the experiences in the design and development of Klaim. Its main purpose is to outline the theoretical foundations of the main features of Klaim and its programming model. We also present a modal logic that permits reasoning about behavioural properties of systems and various type systems that help in controlling agents movements and actions. Extensions of the language in the direction of object oriented programming are also discussed together with the description of the implementation efforts which have lead to the current prototypes.

KLAVA: a Java package for distributed and mobile applications

Highly distributed networks have now become a common infrastructure for wide‐area distributed applications whose key design principle is network awareness, namely the ability to deal with dynamic changes of the network environment. Network‐aware computing has called for new programming languages that exploit the mobility paradigm as a basic interaction mechanism. In this paper we present the architecture of KLAVA, an experimental Java package for distributed applications and code mobility. We describe how KLAVA permits code mobility by relying on Java and present a few distributed applications that exploit mobile code programmed in KLAVA. Copyright

Interactive mobile agents in X-KLAIM

Mobile agents are processes which can migrate and execute on new hosts. Mobility is a key concept for network programming; it has stimulated much research about new programming languages and paradigms. X-KLAIM is an experimental programming language, inspired by the Linda paradigm, where mobile agents and their interaction strategies can be naturally programmed. A prototype implementation of X-KLAIM is presented, together with a few examples introducing the new programming style.

Translating Strong Mobility into Weak Mobility

Mobile agents are software objects that can be transmitted over the net together with data and code, or can autonomously migrate to a remote computer and execute automatically on arrival.Ho wever many frameworks and languages for mobile agents only provide weak mobility: agents do not resume their execution from the instruction following the migration action, instead they are always restarted from a given point. In this paper we present a purely syntactic translation process for transforming programs that use strong mobility into programs that rely only on weak mobility, while preserving the original semantics.This transformation applies to programs written in a procedural language and can be adapted to other languages, like Java, that provide means to send data and code, but not the execution state.It has actually been exploited for implementing our language for mobile agents X-KLAIM, that has linguistic constructs for strong mobility.

Compositional type-checking for delta-oriented programming

Delta-oriented programming is a compositional approach to flexibly implementing software product lines. A product line is represented by a code base and a product line declaration. The code base consists of a set of delta modules specifying modifications to object-oriented programs. The product line declaration provides the connection of the delta modules with the product features. This separation increases the reusability of delta modules. In this paper, we provide a foundation for compositional type checking of delta-oriented product lines of Java programs by presenting a minimal core calculus for delta-oriented programming. The calculus is equipped with a constraint-based type system that allows analyzing each delta module in isolation, such that that also the results of the analysis can be reused. By combining the analysis results for the delta modules with the product line declaration it is possible to establish that all the products of the product line are well-typed according to the Java type system.

Software update via mobile agent based programming

We describe a system that permits maintaining the software installed on several heterogeneous computers distributed over a network by taking advantage of the mobile agent paradigm. The applications are installed and updated only on the central server. When a new release of an application is installed on the server, agents are scattered along the network to update the application on the clients.To build a prototype system we use X-KLAIM, a programming language specifically designed to program distributed systems composed of several components interacting through multiple tuple spaces and mobile code.

Compositional type checking of delta-oriented software product lines

Delta-oriented programming is a compositional approach to flexibly implementing software product lines. A product line is represented by a code base and a product line declaration. The code base consists of a set of delta modules specifying modifications to object-oriented programs. A particular product in a delta-oriented product line is generated by applying the modifications contained in the suitable delta modules to the empty program. The product-line declaration provides the connection of the delta modules with the product features. This separation increases the reusability of delta modules. In this paper, we provide a foundation for compositional type checking of delta-oriented product lines of Java programs by presenting a minimal core calculus for delta-oriented programming. The calculus is equipped with a constraint-based type system that allows analyzing each delta module in isolation, such that the results of the analysis can be reused. By relying only on the analysis results for the delta modules and on the product line declaration, it is possible to establish whether all the products of the product line are well typed according to the fragment of the Java type system modeled by the calculus.