Martina De Sanctis

Design for Adaptation of Distributed Service-Based Systems

Internet of Services applications need to cope with a continuously changing environment, both in terms of the context in which they operate, and of the services, users and providers involved. In this setting, adaptivity is to be considered an intrinsic characteristic of applications rather than an exception to be handled. In this paper we propose a design for adaptation approach that fully exploits the advantages of the service-oriented paradigm to support the development and operation of service-based applications operating in highly dynamic environments. The approach is based on dynamic and incremental service composition and re-configuration techniques and is evaluated on a real-world scenario in the Smart Cities domain.

Enabling Performance Antipatterns to Arise from an ADL-based Software Architecture

While the performance analysis of a software architecture is a quite well-assessed task nowadays, the issue of interpreting the performance results for providing feedback to software architects is still very critical. This is mostly due to the gap between results representation (i.e. mean values, variances, and/or probability distributions) and expected feedback (i.e. architectural alternatives). Performance antipatterns represent effective instruments to tackle this issue, because they document common mistakes leading to performance problems as well as their solutions. In this paper we present a model-driven approach that enables performance antipatterns to arise in the context of an ADL-based software architecture. Such approach automatically detects them in AEmilia, i.e. an ADL allowing the performance evaluation of software systems. The approach has been applied to a case study, and experimental results demonstrate its effectiveness.

Incremental Composition for Adaptive By-Design Service Based Systems

A key challenge posed by the Internet of Services is that applications need to cope with a continuously changing environment, both in terms of the context in which they operate and of the services, users and providers involved. Differently from applications where traditional change detection and adaptation mechanisms can be used, the Internet of Services requires systems that are adaptive by design. In this paper we present a design for adaptation framework supporting the modeling, development and operation of service based applications operating in highly dynamic environments. The approach exploits advanced techniques for dynamic and incremental service composition, allowing to effectively deal with changes occurring at different levels in the system. An implementation of the proposed solution is presented and evaluated on a real-world scenario from the Smart Urban Mobility domain.

Decentralized Dynamic Adaptation for Service-Based Collective Adaptive Systems

Modern service-based systems are progressively becoming more heterogeneous. They form a socio-technical system, composed of distributed entities, software and human participants, interacting with and within the environment. These systems operate under constant perturbations that are due to unexpected changes in the environment and to the unpredictable behavior of the participants. We argue that for a service-based system to be resilient, adaptation must be collective. Multiple participants must adapt their behavior in concert to respond to critical runtime impediments. In this work, we present a framework for the modeling and execution of large-scale service-based Collective Adaptive Systems, where adaptation needs are solved in a decentralized and collective manner.

DeMOCAS: Domain Objects for Service-Based Collective Adaptive Systems

DeMOCAS is a framework for the modeling and execution of service-based collective adaptive systems operating in dynamic environments. In this framework, we apply the Domain Object model and a Collective Adaptation algorithm to a case study from the mobility domain and we show its advantages in handling large-scale, decentralized and adaptive applications.

Domain Objects for Dynamic and Incremental Service Composition

A key feature of service-based applications (SBAs) is the capacity to dynamically define the composition of services independently available, which is required to achieve user goals. For this reason, to effectively deal with the obstacles due to continuous context changes, an incremental refinement of provided services is needed. We propose a new model that allows service functionalities to be defined partially, through the use of abstract activities. The refinement of these activities is postponed and performed incrementally at runtime, using the actual context as a guide. Our approach lets a service provider avoid the hard-coding of all service functionalities and their possible compositions at design time, delaying their refinement until the execution phase. Consequently the whole SBA’s design becomes modular and flexible to better meet the typical dynamism of SBA. We illustrate the approach through an example scenario from the urban mobility domain.

A model-driven approach to catch performance antipatterns in ADL specifications

Context: While the performance analysis of a software architecture is a quite well-assessed task nowadays, the issue of interpreting the performance results for providing feedback to software architects is still very critical. Performance antipatterns represent effective instruments to tackle this issue, because they document common mistakes leading to performance problems as well as their solutions.Objective: Up today performance antipatterns have been only studied in the context of software modeling languages like UML, whereas in this manuscript our objective is to catch them in the context of ADL-based software architectures to investigate their effectiveness.Method: We have implemented a model-driven approach that allows the automatic detection of four performance antipatterns in AEmilia, that is a stochastic process algebraic ADL for performance-aware component-oriented modeling of software systems.Results: We evaluate the approach by applying it to three case studies in different application domains. Experimental results demonstrate the effectiveness of our approach to support the performance improvement of ADL-based software architectures.Conclusion: We can conclude that the detection of performance antipatterns, from the earliest stages of software development, represents an effective instrument to tackle the issue of identifying flaws and improving system performance.

ATLAS: A World-Wide Travel Assistant Exploiting Service-Based Adaptive Technologies.

Nowadays, users can count on a large amount of mobility services offering disparate functionalities and providing all needed information. Yet, from a user perspective, properly exploiting the available mobility services to organize journeys meeting personal expectations, is becoming a complex task. Indeed, discover and select the appropriate services in an open and constantly expanding domain, is a challenging and time-consuming task. We claim that a uniform and easy way for exploiting these services while moving around, getting accurate and personalized information is still missing. In this paper we propose a platform for the definition of value-added mobility services by (i) enhancing interoperability among the existing services, (ii) supporting their execution via run-time adaptation, (iii) through the definition of multi-channel front-end applications. On top of the platform, we have implemented and evaluated a world-wide travel assistant.

Distributed Service Co-evolution Based on Domain Objects

Service evolution is a critical ingredient of the service life-cycle. The more our society depends on large-scale, complex service environments including cloud and mobile services, the more pressing becomes the question of how to evolve a service on the fly at runtime, without bringing whole systems to a halt, due to unintended percolation of evolution effects through service inter–dependency chains. Thus, there is an urgent need for coordinated service evolution (co-evolution). This paper contributes a conceptual solution for dynamic, on-the-fly co-evolution of services, as well as a framework that supports the engineering of such co-evolution support. Our solution is built on top of the Domain Objects architectural concept and service-oriented computing model. We also analyze the types of changes that might happen in a service and their potential impact on dependent clients and servers, and discuss the benefits of our approach on those service co-evolution scenarios.

CAStlE: A Tool for Collective Adaptive Systems Engineering

In this paper we propose CAStlE, a MDE approach to enhance Collective Adaptive System (CAS) specification. In particular, we introduce a domain-specific language (DSL) made-up of three main views: one devoted to adaptive systems design; one addressing ensembles definition; and one tackling the collective adaptation. These three separate aspects are woven seamlessly by the DSL to constitute a complete CAS design. Moreover, each of the defined views conveys the creation of a corresponding model editor, which allows for the three aspects of a CAS to be independently designed by CAStlE.