Marco Pistore

NuSMV 2: An OpenSource Tool for Symbolic Model Checking

This paper describes version 2 of the NuSMV tool. NuSMV is a symbolic model checker originated from the reengineering, reimplementation and extension of SMV, the original BDD-based model checker developed at CMU [15]. The NuSMV project aims at the development of a state-of-the-art symbolic model checker, designed to be applicable in technology transfer projects: it is a well structured, open, flexible and documented platform for model checking, and is robust and close to industrial systems standards [6].

Automated composition of semantic web services into executable processes

Different planning techniques have been applied to the problem of automated composition of web services. However, in realistic cases, this planning problem is far from trivial: the planner needs to deal with the nondeterministic behavior of web services, the partial observability of their internal status, and with complex goals expressing temporal conditions and preference requirements. We propose a planning technique for the automated composition of web services described in OWLS process models, which can deal effectively with nondeterminism, partial observability, and complex goals. The technique allows for the synthesis of plans that encode compositions of web services with the usual programming constructs, like conditionals and iterations. The generated plans can thus be translated into executable processes, e.g., BPEL4WS programs. We implement our solution in a planner and do some preliminary experimental evaluations that show the potentialities of our approach, and the gain in performance of automating the composition at the semantic level w.r.t. the automated composition at the level of executable processes.

Automated composition of Web services via planning in asynchronous domains

We propose a novel planning framework for the automated composition of web services. We consider services that are specified and implemented in industrial standard languages for business processes modeling and execution, like BPEL4WS. These languages describe web services whose behavior is intrinsically asynchronous. For this reason, the key aspect of our framework is the modeling of asynchronous planning problems. In the paper we describe the framework and propose a planning approach that is based on state of the art techniques for planning under uncertainty. Our experiments show that this approach can scale up to significant cases, i.e., to cases in which the manual development of BPEL4WS composed services is not trivial and is time consuming.

Planning and Monitoring Web Service Composition

The ability to automatically compose web services, and to monitor their execution, is an essential step to substantially decrease time and costs in the development, integration, and maintenance of complex services. In this paper, we exploit techniques based on the “Planning as Model Checking” approach to automatically compose web services and synthesize monitoring components. By relying on such a flexible technology, we are able to deal with the difficulties stemming from the unpredictability of external partner services, the opaqueness of their internal status, and the presence of complex behavioral requirements. We test our approach on a simple, yet realistic example; the results provide a witness to the potentiality of this approach.

Specifying and analyzing early requirements in Tropos

We present a framework that supports the formal verification of early requirements specifications. The framework is based on Formal Tropos, a specification language that adopts primitive concepts for modeling early requirements (such as actor, goal, and strategic dependency), along with a rich temporal specification language. We show how existing formal analysis techniques, and in particular model checking, can be adapted for the automatic verification of Formal Tropos specifications. These techniques have been implemented in a tool, called the T-Tool, that maps Formal Tropos specifications into a language that can be handled by the NuSMV model checker. Finally, we evaluate our methodology on a course-exam management case study. Our experiments show that formal analysis reveals gaps and inconsistencies in early requirements specifications that are by no means trivial to discover without the help of formal analysis tools.

Model checking early requirements specifications in Tropos

We describe an attempt to bridge the gap between early requirements specification and formal methods. In particular, we propose a new specification language, called Formal Tropos, that is founded on the primitive concepts of early requirements frameworks (actor, goal, strategic dependency) (Yu, 1997), but supplements them with a rich temporal specification language. We also extend existing formal analysis techniques, in particular model checking, to allow for an automatic verification of relevant properties for an early requirements specification. Our preliminary experiments demonstrate that formal analysis reveals gaps and inconsistencies in early requirements that are by no means trivial to discover without the help of formal analysis tools.

Automated synthesis of composite BPEL4WS Web services

In this paper we propose a technique for the automated synthesis of new composite Web services. Given a set of abstract BPEL4WS descriptions of component services, and a composition requirement, we automatically generate an executable BPEL4WS process that, once deployed, is able to interact with the components to satisfy the requirement. We implement the proposed approach exploiting efficient synthesis techniques, and experiment with some case studies taken from real world applications and with a parameterized domain. We show that the technique can scale up to cases in, which the manual development of BPEL4WS composite services is not trivial and is time consuming.

Analysis of communication models in web service compositions

In this paper we describe an approach for the verification of Web service compositions defined by sets of BPEL processes. The key aspect of such a verification is the model adopted for representing the communications among the services participating in the composition. Indeed, these communications are asynchronous and buffered in the existing execution frameworks, while most verification approaches assume a synchronous communication model for efficiency reasons. In our approach, we develop a parametric model for describing Web service compositions, which allows us to capture a hierarchy of communication models, ranging from synchronous communications to asynchronous communications with complex buffer structures. Moreover, we develop a technique to associate with a Web service composition the most adequate communication model, i.e., the simplest model that is sufficient to capture all the behaviors of the composition. This way, we can provide an accurate model of a wider class of service composition scenarios, while preserving as much as possible an efficient performance in verification.

A Request Language for Web-Services Based on Planning and Constraint Satisfaction

One of the most challenging problems that web-service enabled e-marketplaces face is the lack of support for appropriate service request languages that retrieve and aggregate services relevant to a business problem. We present an architectural framework for web-service interaction based on planning and constraint satisfaction, and a webservice request language (WSRL) developed on the basis of this framework. This framework is capable of performing planning under uncertainty on the basis of refinement and revision as new service-related information is accumulated (via interaction withth e user or UDDI) and as execution circumstances necessitate change.

A framework for integrating business processes and business requirements

Service-oriented architectures and Web service infrastructure provide the ideal framework for interconnecting organizations and for defining distributed business applications. The possibility to exploit business process definition and execution languages is particularly relevant for capturing the process-oriented nature of these applications. However, business processes by themselves are not enough to manage the changes and to allow an organization to continuously adapt its business model to the typical needs of distributed applications. To achieve this flexibility, it is of uttermost importance to link the business processes to the organizational strategy and to the business goals that motivate the need of these processes. We propose a framework for representing strategies and goals of an organization in terms of business requirements. The framework allows to describe how an organizational strategy is operationalized into activities and implemented by business processes. It also allows to represent the assumptions on the interactions between the different business applications. Finally, this framework allows for the usage of formal analysis techniques, in particular model checking, to pinpoint problems and to identify possible solutions in this domain.