Section: Application Domains

Software components monitoring

Web-services, i.e., services that are provided, controlled and managed through Internet, cover nowadays more and more application areas, from travel booking to goods supplying in supermarkets or the management of an e-learning platform. Such applications need to process requests from users and other services on line, and respond accurately in real time. Anyway, errors may occur, which need to be addressed in order to still be able to provide the correct response with a satisfactory quality of service (QoS): on-line monitoring, especially diagnosis and repair capabilities, become then a crucial concern.

We have been working on this problem within the WS-DIAMOND project [63] , a large European funded project involving eight partners in Italy, France, Austria and Netherlands http://wsdiamond.di.unito.it/ . Our own work consisted in two distinct contributions:

The first contribution has been to extend the decentralized component-oriented approach, initially developed for monitoring telecommunication networks [3] to this new domain. To this end we have proposed the concept of distributed chronicles, with synchronization events, and the design of an architecture consisting of distributed CRSs (Chronicle Recognition Systems) communicating their local diagnoses to a broker agent which is in charge of merging them to compute a global diagnosis. During his thesis, X. Le Guillou developped two approaches for solving this problem [46] , [47] , [48] .

The second one was in formally characterizing the intended system properties such as the diagnosability (i.e. the capability to detect and explain an error in due time) and repairability (i.e. the capability to get the system back to correctness, in due time), managing to relate them in order to define a so-called 'self-healability' property which will ensure the system is self-healing, i.e. it can always match a set of observations to an adequate repair procedure, which will resolve any of the faults which are consistent with the observations [31] .

Our current work aims at coupling diagnosing and repair, in order to get adaptive web services. We started this study by proposing an architecture inspired from the one developed during the WS-DIAMOND project and dedicated to the adaptive process of a request event when faults occur and propagate through the orchestration.