Web services technologies are mainly dealing with programmatic access and interactions between software services. On the other hand, we witness the so-called Web 2.0 content- and people-oriented approaches increasingly gaining momentum on the Internet. Such interactions span both, humans and software services, thus viable solutions need to cater for highly dynamic and complex interactions. This makes the development and management of (service) interactions challenging as current tools do not sufficiently address those dynamic aspects in coordination and communications, including QoS and mobility issues. In this keynote talk the main challenges towards building the required novel conceptual abstractions as well as needed technological implementations are presented and discussed.

The greater and greater quantity of services that are available over the web causes a growing attention to techniques that facilitate their reuse. A web service specification can be quite complex, including various operations and message exchange patterns. In this work, we focus on the problem of retrieving a web service, which can play a given choreography role, preserving at the same time a condition of interest (the goal to satisfy which the service is sought). We show that current semantic matchmaking techniques do not guarantee goal preservation. We also show an approach for overcoming these limits, which exploits the choreography definition. This work is based on an action-based representation of the operations of a service: each operation is described in terms of its preconditions and effects, without taking into account the ontology layer which is not functional to the aims of the work.

Using Web services for business process automation is an accepted approach in context of service-oriented architectures (SOA). Business process models are created by business experts usually not having an IT background and who are therefore not able to use the technical descriptions available for web services. In this paper, we show how we extended the market leading business process management suite ARIS to enable business experts to discover, assess, and select Web services for business process automation. We developed a structural and a semantic matching algorithm as well as a graphical user interface for Web service assessment. We use a schema to classify Web service discovery literature and we relate our work to it. Our completely integrated discovery tool helps bridging the gap between business and IT, because business experts can now discover Web services needed for business process automation on their own.

In recent years a huge amount of effort and money has been invested in the area of semantic service discovery and presented ap- proaches have become more sophisticated and mature. Nevertheless sur- prisingly little effort is being put into the evaluation of these approaches. We argue that the lack of established and theoretically well-founded methodologies and test beds for comparative evaluation of semantic ser- vice discovery is a major blocker of the advancement of the ¯eld. To lay the ground for a comprehensive treatment of this problem we discuss the applicability of well-known evaluation methodologies from informa- tion retrieval and provide an exhaustive survey of the current evaluation approaches.

Dynamic composition of web services is a promising approach and at the same time a challenging research areas for the dissemination of serviceoriented applications. It is widely recognised that service semantics is a key element for the dynamic composition of Web services since it allows the unambiguous descriptions of a service’s capabilities and parameters. This paper introduces a framework for performing dynamic service composition by exploiting the semantic matchmaking between service parameters (i.e., outputs and inputs) to enable their interconnection and interaction. The basic assumption of the framework is that matchmaking enables finding semantic compatibilities among independently defined service descriptions. We also developed a composition algorithm that follows a semantic graph-based approach, in which a graph represents service compositions and the nodes of this graph represent semantic connections between services. Moreover, functional and non-functional properties of services are considered to ensure the computation of relevant and best service compositions for some service request. The suggested end-to-end functional level service composition framework is illustrated with a realistic application scenario from the IST-SPICE project.

Currently, composition of web services is done by orchestration. An orchestration is a workflow that combines invocations of individual operations of the web services involved. It is therefore a composition of individual operations, rather than a composition of entire web services. In this paper we propose a different approach to web service composition, whereby entire services are composed into composite services. The latter are again entire web services, that is, they can be further composed using our composition, or they can be used in an orchestration. We show how these composite services can be constructed hierarchically and used in practice.

Aside from business processes, the service-oriented approach currently realized with Web services and BPEL should be utilizable for data-intensive applications as well. Fundamentally, data-intensive applications are characterized by (i) a sequence of functional operations processing large amounts of data and (ii) the delivery and transformation of huge data sets between those functional activities. However, for the efficient handling of massive data sets, a significant amount of data infrastructure is required and the predefined 'by value' data semantic within the invocation of Web services and BPEL is not well suited for this context. To tackle this problem on the BPEL level, we developed a seamless extension to BPEL - the 'BPEL data transitions.

Service orientation is the de-facto architectural style, today. But, what actually is a service and how should service boundaries be chosen? Resource orientation, once seen as a ”light-weight” approach to web services, is reshaping itself as a modeling strategy to service orientation. Along comes the realization that resources are in-fact complex state machines. Currently, there is no accepted standard for modeling the internal state of resources. In this paper, BPEL is proposed as a modeling language for resources and necessary extensions to BPEL are outlined.

Key establishment is essential for many applications of cryptography. Its purpose is to negotiate keys for other cryptographic schemes, usually for encryption and authentication. In a web services context, WS-SecureConversation has been specified to make use of negotiated keys. The most popular key establishment scheme in the Internet is the (handshake protocol of the) Secure Socket Layer or Transport Layer Security protocol (SSL/TLS). However, SSL/TLS has primarily been designed to secure HTTP, by encrypting and authenticating TCP connections. It is thus not usable to negotiate keys in SOAP connections with intermediaries. We propose SSL-over-SOAP, a family of key establishment protocols for Web services. It is based the design of the SSL handshake, so security analysis results for standard SSL/TLS apply to our new proposal. We have implemented this protocol in the framework ofWS-Trust and WS-SecureConversation.

The effective and efficient exploitation of Grid computing facilities require advanced resource management systems to automatically and transparently ensure the fulfillment not only of functional requirements but also of non-functional ones. This paper presents a framework for brokering of Grid resources, virtualized through Web Services, which can be dynamically configured with respect to multiple syntactic and semantic description languages and related matching strategies. Hence, it discovers and selects resources and automatically allocates application tasks to them on the basis of both functional and quality of service (QoS) requirements. In particular the paper presents the framework specialization which aims to select a pool of resources whose overall performance allows for satisfying time and cost constraints for the execution of an application partitioned in concurrent tasks according to the data parallelism pattern.

Service engineering and service-oriented architecture as an integration and platform technology is a recent approach to software systems integration. Software quality aspects such as performance are of central importance for the integration of heterogeneous, distributed service-based systems. Empirical performance evaluation is a process of measuring and calculating performance metrics of the implemented software. We present an approach for the empirical, model-based performance evaluation of services and service compositions in the context of model-driven service engineering. Temporal databases theory is utilised for the empirical performance evaluation of model-driven developed service systems.