José Antonio Mateo

A centralized and a decentralized method to automatically derive choreography-conforming web service systems☆

Abstract We present a formal model to represent orchestrations and choreographies and we define several conformance semantic relations allowing to detect whether a set of orchestration models, representing some web services, leads to the overall communications described in a choreography. Given this formal model, we develop automatic methods to derive a set of web services from a given choreography, in such a way that the system consisting of these services necessarily conforms to the choreography. These methods enable the construction of conforming systems of services even in cases where projecting the choreography into each service would lead to a non-conforming system. This issue is addressed by adding some control messages that make services interact as required by the choreography. Two different derivation methods are presented. In the centralized method, a new service is responsible of managing these additional control messages. In the decentralized method, the responsibility of handling these messages is distributed among all services.

Petri nets-based model for the analysis of NORIA protocol

Network rOle‐based Routing Intelligent Algorithm is a novel routing algorithm for wireless sensor networks, which combine various effective techniques in order to reduce energy consumption and improve data routes. This algorithm uses role assignment for distributing tasks over the network nodes and fuzzy logic for making decisions. There is a clear need for the use of formal methods to validate the correctness of the protocols as well as performance and functionality prior to the deployment of such algorithms in a real environment. This paper presents a formal and rigorous study of Network rOle‐based Routing Intelligent Algorithm. Prioritised‐timed coloured petri nets (PTCPNs) have been chosen as an appropriate modelling language. In this way, PTCPNs have been used to describe complete and unambiguous specifications of system behaviour, whereas CPNTools is used to evaluate the correctness of the protocol using state space exploration and for performance evaluation using simulation. Copyright

A Coloured Petri Net Approach to Model and Analyse Stateful Workflows Based on WS-BPEL and WSRF

Composite Web services technologies are widely used due to their ability to provide interoperability among services from different companies. Web services are usually stateless, which means that no state is stored from the clients viewpoint. However, some new applications and services require to capture the state of some resources after each computation. Thus, new standards to model Web services states have emerged e.g. Web Services Resource Framework (WSRF). In this paper, we present a formal model based on WS-BPEL and WSRF, and we provide a prioritised-timed coloured Petri net semantics for it. This semantics captures the main activities of WS-BPEL, but we also consider other important aspects, both from WS-BPEL and WSRF, such as fault handling, resource management, time-outs and a publish-subscribe system.

An operational semantics of BPEL orchestrations integrating web services resource framework

Web service compositions are gaining increasingly attention for the development of complex web systems by combination of existing ones. In this paper, we present a formal framework that integrates a well-known business process language (BPEL) with a recent technology for describing distributed resources throughout the Internet (WSRF). We define an operational semantics for a language that integrates both approaches taking into account the main features of them, such as notifications, event handling, fault handling and timed constraints.

DIEGO: A Tool for DerIving chorEoGraphy-cOnforming Web Service Systems

We present a tool to automatically derive choreography-conforming web services systems. The user provides a specification that describes peer-to-peer collaborations of the observable behavior of parties from a global viewpoint, in our case WS-CDL documents, and the tool automatically extracts the particular behavior of each participant, more concretely, WS-BPEL documents defining the behavior from a local viewpoint. We implement two automatic methods(centralized and decentralized) that derive conforming systems even in cases where projecting the choreography into each service would lead to a non-conforming system. This issue is addressed by adding some control messages that make services interact as required by the choreography. Experiments where the number of exchanged messages is measured are presented, and strategies to reduce the number of these messages are discussed.

Probabilistic model checking: one step forward in wireless sensor networks simulation

A novel collision resolution algorithm for wireless sensor networks is formally analysed via probabilistic model checking. The algorithm called 2CS-WSN is specifically designed to be used during the contention phase of IEEE 802.15.4. Discrete time Markov chains (DTMCs) have been proposed as modelling formalism and the well-known probabilistic symbolic model checker PRISM is used to check some correctness properties and different operating modes and, furthermore, to collect some performance measures. Thus, all the benefits of formal verification and simulation are gathered. These correctness properties as well as practical and relevant scenarios for the real world have agreed with the algorithm designers.

Formal Study of a Novel Network Role-based Routing Intelligent Algorithm☆☆☆

Abstract NORIA (Network rOle-based Routing Intelligent Algorithm) is a novel routing algorithm for Wireless Sensor Networks (WSNs) which combines various effective techniques in order to reduce energy consumption and improve data routes. This paper presents a formal and rigorous study of NORIA. Prioritised-Timed Coloured Petri Nets (PTCPNs) have been used to describe complete and unambiguous specifications of system behaviour, whereas CPNTools is used to evaluate the correctness of the protocol using state space exploration.

Improving the Automatic Derivation of Choreography-conforming Web Services Systems

Abstract We present DIEGO 2.0, a new version of our tool DIEGO. Given a WS-CDL choreography, it automatically ex-tracts a set of WS-BPEL web services such that, if these services interact with each other, they necessarily produce the behavior defined in the choreography even if the natural projection does not work. This is achieved by introducing some control messages which make services coordinate as expected. The main improvement with respect to the pre-vious version of the tool is that the number of these messages has been dramatically reduced. We formally define the new derivation, prove its correctness, and empirically compare the efficiency of new and former derivation algorithms. We also introduce other improvements of the new tool version, such as the testing engine.

Formal Analysis of an Energy-aware Collision Resolution Protocol for Wireless Sensor Networks

Abstract This paper provides a comprehensive and rigorous study of a novel collision resolution algorithm for wireless sensor networks: 2CS-WSN. It is specifically designed to be used during the contention phase of IEEE 802.15.4. This algorithm has been modelled in terms of discrete time Markov chains (DTMCs) and, using the probabilistic symbolic model checker PRISM, correctness properties and different operation modes of the algorithm have been studied. Moreover, different model abstractions have been used in order to identify any inconsistencies or ambiguities, and to prove interesting properties for non-trivial, practical and relevant scenarios. Finally, since the biggest source of energy waste is the collision, this paper conducts a wide study of energy saving in this algorithm.

Conformance Verification of Normative Specifications using C-O Diagrams

C-O Diagrams have been introduced as a means to have a visual representation of normative texts and electronic contracts, where it is possible to represent the obligations, permissions and prohibitions of the different signatories, as well as what are the penalties in case of not fulfillment of their obligations and prohibitions. In such diagrams we are also able to represent absolute and relative timing constrains. In this paper we consider a formal semantics for C-O Diagrams based on a network of timed automata and we present several relations to check the consistency of a contract in terms of realizability, to analyze whether an implementation satisfies the requirements defined on its contract, and to compare several implementations using the executed permissions as criteria.