Guglielmo De Angelis

Model-Based Generation of Testbeds for Web Services

A Web Service is commonly not an independent software entity, but plays a role in some business process. Hence, it depends on the services provided by external Web Services, to provide its own service. While developing and testing a Web Service, such external services are not always available, or their usage comes along with unwanted side effects like, e.g., utilization fees or database modifications. We present a model-based approach to generate stubs for Web Services which respect both an extra-functional contract expressed via a Service Level Agreement (SLA), and a functional contract modeled via a state machine. These stubs allow a developer to set up a testbed over the target platform, in which the extra-functional and functional behavior of a Web Service under development can be tested before its publication.

The PLASTIC Framework and Tools for Testing Service-Oriented Applications

The emergence of the Service Oriented Architecture (SOA) is changing the way in which software applications are developed. A service-oriented application consists of the dynamic composition of autonomous services independently developed by different organizations and deployed on heterogenous networks. Therefore, validation of SOA poses several new challenges, without offering any discount for the more traditional testing problems. In this chapter we overview the PLASTIC validation framework in which different techniques can be combined for the verification of both functional and extra-functional properties, spanning over both off-line and on-line testing stages. The former stage concerns development time testing, at which services are exercised in a simulated environment. The latter foresees the monitoring of a service live usage, to dynamically reveal possible deviations from the expected behaviour. Some techniques and tools which fit within the outlined framework are presented.

A QoS test-bed generator for web services

In the last years both industry and academia have shown a great interest in ensuring consistent cooperation for business-critical services, with contractually agreed levels of Quality of Service. Service Level Agreement specifications as well as techniques for their evaluation are nowadays irremissible assets. This paper presents Puppet (Pick UP Performance Evaluation Test-bed), an approach and a tool for the automatic generation of test-beds to empirically evaluate the QoS features of a Web Service under development. Specifically, the generation exploits the information about the coordinating scenario (be it choreography or orchestration), the service description (WSDL) and the specification of the agreements (WS-Agreement).

An integrated development and runtime environment for the future internet

The Future Internet environments raise challenging issues for the Service-Oriented Architectures. Due to the scalability and heterogeneity issues new approaches are thought in order to leverage the SOA to support a wider range of services and users. The CHOReOS project is part of the European Community Initiative to sketch technological solutions for the future ultra large systems. In particular, CHOReOS explores the choreography of services paradigm. Within this project, a conceptual architecture combining both the development and runtime environments is realized. This chapter introduces the CHOReOS Integrated Development and Runtime Environment, aka IDRE.

Is my model right? Let me ask the expert

Abstract: Defining a domain model is a costly and error-prone process. It requires that the knowledge possessed by domain experts be suitably captured by modeling experts. Eliciting what is in the domain experts mind and expressing it using a modeling language involve substantial human effort. In the process, conceptual errors may be introduced that are hard to detect without a suitable validation methodology. This paper proposes an approach to support such validation, by reducing the knowledge gap that separates modeling experts and domain experts. While our methodology still requires the domain experts judgement, it partially automates the validation process by generating a set of yes/no questions from the model. Answers differing from expected ones point to elements in the model which require further consideration and can be used to guide the dialogue between domain experts and modeling experts. Our methodology was implemented as a tool and was applied to a real case study, within the IPERMOB project.

Scaling up SLA monitoring in pervasive environments

Service level agreements (SLA) are contracts defining the obligations and rights between the provider of a web service and a client with respect to the services quality. An essential component of SLA management is the run-time checking of relevant quality parameters. SLA checking must be precise and continuous to timely detect any possible SLA violations. Available techniques and mechanisms to check SLAs, however, are unlikely to scale to more complex families of SLAs tailored to fit diverse and very large groups of clients whose devices have limited storage and bandwidth capabilities. This challenge results not only in the commitment of valuable resources to SLA checking (reducing the service provider capacity), but it can also trigger additional violations and cause disagreements between client and server due to perceived violations. In this paper we focus on the elaboration of this challenge and on identifying opportunities that arise from the inherent diversity present in scenarios rendering web services in pervasive environments.

Monitoring service choreographies from multiple sources

Modern software applications are more and more conceived as distributed service compositions deployed over Grid and Cloud technologies. Choreographies provide abstract specifications of such compositions, by modeling message-based multi-party interactions without assuming any central coordination. To enable the management and dynamic adaptation of choreographies, it is essential to keep track of events and exchanged messages and to monitor the status of the underlying platform, and combine these different levels of information into complex events meaningful at the application level. Towards this goal, we propose a Multi-source Monitoring Framework that we are developing within the EU Project CHOReOS, which can correlate the messages passed at business-service level with observations relative to the infrastructure resources. We present the monitor architecture and illustrate it on a use-case excerpted from the CHOReOS project.

Automatic generation of test-beds for pre-deployment QoS evaluation of web services

This paper presents Puppet (Pick UP Performance Evaluation Test-bed), an approach for the automatic generation of test-beds to empirically evaluate different QoS features of a Web Service under development. Specifically, the generation exploits the information about the coordinating scenario, the service description and the specification of the agreements that the roles will abide. The approach is supported by a proof-of-concept tool to validate the feasibility of the idea.

Non-functional analysis of service choreographies

A highly important aspect in service compositions is to guarantee the established Quality-of-Service (QoS). However, the modeling of non-functional properties of service choreographies is neglected in the OMG standard BPMN notation, so that other, separate languages should be used to specify QoS constraints and then traced back to the functional BPMN model. We introduced an approach called Q4BPMN by which non-functional requirements can be directly expressed within the BPMN model. This paper leverages Model Driven Engineering (MDE) techniques to automatically handle non-functional properties expressed with Q4BPMN in order to obtain information useful both to highlight intrinsic features of the service choreography and to detect possible model criticalities. Specifically, we transform a Q4BPMN model into the pivot KLAPER notation, on which we can directly exploit the analysis tools within the KLAPERSUITE environment. Hence this paper provides the first step towards automated non-functional analysis of service choreographies.

A Framework for Analyzing and Testing the Performance of Software Services

Networks “Beyond the 3rd Generation” (B3G) are characterized by mobile and resource-limited devices that communicate through different kinds of network interfaces. Software services deployed in such networks shall adapt themselves according to possible execution contexts and requirement changes. At the same time, software services have to be competitive in terms of the Quality of Service (QoS) provided, or perceived by the end user.