'Crowdsourcing' is a relatively recent concept that encompasses many practices. This diversity leads to the blurring of the limits of crowdsourcing that may be identified virtually with any type of internet-based collaborative activity, such as co-creation or user innovation. Varying definitions of crowdsourcing exist, and therefore some authors present certain specific examples of crowdsourcing as paradigmatic, while others present the same examples as the opposite. In this article, existing definitions of crowdsourcing are analysed to extract common elements and to establish the basic characteristics of any crowdsourcing initiative. Based on these existing definitions, an exhaustive and consistent definition for crowdsourcing is presented and contrasted in 11 cases.

/pdf/towards-an-integrated-crowdsourcing-definition-3qoy6yinnl.pdf

Towards an integrated crowdsourcing definition

The Grid 2: Blueprint for a New Computing Infrastructure

We introduce COWS (Calculus for Orchestration of Web Services), a new foundational language for SOC whose design has been influenced by WS-BPEL, the de facto standard language for orchestration of web services. COWS combines in an original way a number of ingredients borrowed from well-known process calculi, e.g. asynchronous communication, polyadic synchronization, pattern matching, protection, delimited receiving and killing activities, while resulting different fromany of them. Several examples illustrates COWS peculiarities and show its expressiveness both for modelling imperative and orchestration constructs, e.g. web services, flow graphs, fault and compensation handlers, and for encoding other process and orchestration languages.

/pdf/a-calculus-for-orchestration-of-web-services-2n5nfwed6v.pdf

A calculus for orchestration of web services

Aligning Observed and Modeled Behavior The availability of process models and event logs is rapidly increasing as more and more business processes are supported by IT. On the one hand, most organizations make substantial efforts to document their processes, while on the other hand, these processes leave footprints in their information systems. Although it is possible to extract event logs from today’s systems, the relation between event logs and process models is often identified using heuristics that may yield misleading insights. In this thesis, techniques to align event logs and process models are explored. Based on the obtained alignments, various analysis techniques are developed. The techniques are evaluated against both artificial and real-life process models and event logs. A memory-efficient technique to compute alignments between event logs and process models has been developed. Given an event log and a process model, low-level deviations, i.e., observed activities that are not allowed according to the model and the other way around, are explicitly identified. The technique can also be used to identify high-level deviations such as swapped and replaced activities. Our technique is applied to problems occurring in different domains. Unlike earlier approaches, alignment-based conformance checking techniques are shown to be robust against peculiarities of process models, such as duplicate and invisible tasks. Alignmentbased conformance metrics, such as fitness and precision, are shown to be more intuitive and can deal with multiple level of noise in event logs. Various visualizations of alignments provide powerful diagnostics to identify the context of frequently occurring deviations between process executions and prescribed process models. Applying data mining techniques to alignments yields root causes of deviations between the observed behavior in an event log and the modeled behavior in a process model. Alignments also improve the robustness of performance measurements based on event logs and process models, even if the logs are deviating from the models. From a computational point of view, computing alignments is extremely expensive. However, the obtained results indicate that alignments not only provide a theoretically solid basis for analysis based on both models and process executions, but are also able to handle problems of real-life complexity.

Aligning observed and modeled behavior

The IST-FET Integrated Project SENSORIA aims at developing a novel comprehensive approach to the engineering of service-oriented software systems where foundational theories, techniques and methods are fully integrated in a pragmatic software engineering approach. Process calculi and logical methods serve as the main mathematical basis of the SENSORIA approach.

In this paper we give first a short overview of SENSORIA and then focus on process calculi for service-oriented computing. The Service Centered Calculus SCC is a general purpose calculus which enriches traditional process calculi with an explicit notion of session; the Service Oriented Computing Kernel SOCK is inspired by the Web services protocol stack and consists of three layers for service description, service engines, and the service network; Performance Evaluation Process Algebra (PEPA) is an expressive formal language for modelling distributed systems which we use for quantitative analysis of services. The calculi and the analysis techniques are illustrated by a case study in the area of distributed e-learning systems.

/pdf/sensoria-process-calculi-for-service-oriented-computing-21dmby4amr.pdf

SENSORIA process calculi for service-oriented computing

/pdf/leveraging-applications-of-formal-methods-verification-and-2jz05aj0gt.pdf

Leveraging Applications of Formal Methods, Verification and Validation

We introduce a logical verification framework for checking functional properties of service-oriented applications formally specified using the service specification language COWS. The properties are described by means of SocL, a logic specifically designed to capture peculiar aspects of services. Service behaviours are abstracted in terms of Doubly Labelled Transition Systems, which are used as the interpretation domain for SocL formulae. We also illustrate the SocL model checker at work on a bank service scenario specified in COWS.

/pdf/a-model-checking-approach-for-verifying-cows-specifications-48e8xiihvx.pdf

A model checking approach for verifying COWS specifications

We introduce a logical verification methodology for checking behavioral properties of service-oriented computing systems. Service properties are described by means of SocL, a branching-time temporal logic that we have specifically designed for expressing in an effective way distinctive aspects of services, such as, acceptance of a request, provision of a response, correlation among service requests and responses, etc. Our approach allows service properties to be expressed in such a way that they can be independent of service domains and specifications. We show an instantiation of our general methodology that uses the formal language COWS to conveniently specify services and the expressly developed software tool CMC to assist the user in the task of verifying SocL formulas over service specifications. We demonstrate the feasibility and effectiveness of our methodology by means of the specification and analysis of a case study in the automotive domain.

/pdf/a-logical-verification-methodology-for-service-oriented-2ps4607fe7.pdf

A logical verification methodology for service-oriented computing

We introduce Blite, a lightweight language for web services orchestration designed around some of WS-BPEL peculiar features like partner links, process termination, message correlation, long-running business transactions and compensation handlers. Blite formal presentation helps clarifying some ambiguous aspects of the WS-BPEL specification, which have led to engines implementing different semantics and, thus, have undermined portability of WS-BPEL programs over different platforms. We illustrate the main features of Blite by means of many examples, some of which are also exploited to test and compare the behaviour of three of the most known free WS-BPEL engines.

/pdf/a-formal-account-of-ws-bpel-1ra2bgfwex.pdf

Alessandro Lapadula

Papers

A calculus for orchestration of web services

Leveraging Applications of Formal Methods, Verification and Validation

A model checking approach for verifying COWS specifications

A logical verification methodology for service-oriented computing

A formal account of WS-BPEL