Andrea Polini

WS-TAXI: A WSDL-based Testing Tool for Web Services

Web Services (WSs) are the W3C-endorsed realization of the Service-Oriented Architecture (SOA). Since they are supposed to be implementation-neutral, WSs are typically tested black-box at their interface. Such an interface is generally specified in an XML-based notation called the WS Description Language (WSDL). Conceptually, these WSDL documents are eligible for fully automated WS test generation using syntax-based testing approaches. Towards such goal, we introduce the WS-TAXI framework, in which we combine the coverage of WS operations with data-driven test generation. In this paper we present an early-stage implementation of WS-TAXI, obtained by the integration of two existing softwares: soapUI, a popular tool for WS testing, and TAXI, an application we have previously developed for the automated derivation of XML instances from a XML schema. WS-TAXI delivers a complete suite of test messages ready for execution. Test generation is driven by basic coverage criteria and by the application of some heuristics. The application of WS-TAXI to a real case study gave encouraging results.

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.

Audition of web services for testing conformance to open specified protocols

A Web Service (WS) is a type of component specifically conceived for distributed machine-to-machine interaction. Interoperability between WSs involves both data and messages exchanged and protocols of usage, and is pursued via the establishment of standard specifications to which service providers must conform. In previous work we have envisaged a framework for WS testing. Within this framework, this paper focuses on how the intended protocol of access for a standard service could be specified, and especially on how the conformance of a service instance to this specified protocol can then be tested. We propose to augment the WSDL description with a UML2.0 Protocol State Machine (PSM) diagram. The PSM is intended to express how, and under which conditions, the service provided by a component through its ports and interfaces can be accessed by a client. We then propose to translate the PSM to a Symbolic Transition System, to which existing formal testing theory and tools can be readily applied for conformance evaluation. A simple example illustrates the approach and highlights the peculiar challenges raised by WS conformance testing.

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.

Enhancing Service Federation Trustworthiness through Online Testing

Security, data protection, trust management, authentication, and authorization are crucial assets in the Internet of Services. Online testing enhances trustworthiness among federated services that are often independently developed, deployed, and maintained.

Business Processes Verification for e-Government Service Delivery

Domain experts knowledge represents a major source of information in the design and the development of user-centric and distributed service-based applications, such as those of e-government. Issues related both to the communication among domain and IT experts, and to the implementation of domain dependent requirements in service-based applications, have to be carefully considered to support both Public Administrations efficiency and citizen satisfaction. In this article, we provide as user-friendly approach toward business process assessment via formal verification. Starting from a semi-formal notation, well understood and largely used by domain experts, we provide a mapping to a formal specification in the form of a process algebra. This transformation makes possible formal and automatic verification of desired quality requirements. The approach has been already applied, with encouraging results, in the e-government domain to verify the quality of business processes related to the delivery of e-government digital services to citizens. Moreover, the approach is supported by a plug-in for the Eclipse platform permitting to have an integrated environment in which to design the process model and to assess its quality.

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.

An Operational Semantics of BPMN Collaboration

In the last years we are observing a growing interest in formalising the execution semantics of business process modelling languages that, despite their lack of formal characterisation, are widely adopted in industry and academia. In this paper, we focus on the OMG standard BPMN 2.0. Specifically, we provide a direct formalisation of its operational semantics in terms of Labelled Transition Systems LTS. This approach permits both to avoid possible miss-interpretations due to the usage of the natural language in the specification of the standard, and to overcome issues due to the mapping of BPMN to other formal languages, which are equipped with their own semantics. In addition, it paves the way for the use of consolidated formal reasoning techniques based on LTS e.g., model checking. Our operational semantics is given for a relevant subset of BPMN elements focusing on the capability to model collaborations among organisations via message exchange. Moreover, one of its distinctive aspects is the suitability to model business processes with arbitrary topology. This allows designers to freely specify their processes according to the reality without the need of defining well-structured models. We illustrate our approach through a simple, yet realistic, running example about commercial transactions.

Direct Verification of BPMN Processes through an Optimized Unfolding Technique

Business process analysis is one of the most important and complex activities of Business Process Management. Business processes are typically defined by business experts which ask for graphical and user-friendly notations. Nevertheless most notations used typically lack precisely defined semantics limiting the possibility of analysis to informal approaches such as observation techniques. To support formal verification techniques it is necessary to define a precise mapping between the adopted user-friendly notation and a formal language. In this paper we propose a Java based verification approach for Business Processes modeled using the BPMN 2.0 standard. In particular, we defined a precise Java mapping for the main elements of the BPMN 2.0 notation. The relations among the different elements of a BPMN 2.0 specification are supported by the inclusion of specific attributes and methods in the created Java objects. The behavior of a set of interrelated objects, corresponding to a BPMN 2.0 specification, can be explored using an algorithm we defined for the purpose. Such an algorithm permits to avoid the state explosion phenomenon using an ad-hoc unfolding technique. A plug-in for the Eclipse IDE platform has been developed. It permits to have an integrated environment in which to design a business process, to verify it, and to check the result of the verification in order to improve the business process itself. This iterative approach can continue until all the issues highlighted by the verifier are solved. The approach and the prototype have been successfully applied to real scenarios within the Public Administration domain, with encouraging results.

Architectural verification of black-box component-based systems

We introduce an original approach, which combines monitoring and model checking techniques into a comprehensive methodology for the architectural verification of Component-based systems. The approach works by first capturing the traces of execution via the instrumented middleware; then, the observed traces are reverse engineered into Message Sequence Charts, which are then checked for compliance to the Component-based Software Architecture, using a model checker. The methodology has been conceived for being applied indifferently for validating the system in house before deployment and for continuous validation in the field following evolution. A case study for the first case is here illustrated.