Eduardo Goncalves da Silva

A Framework for Dynamic Web Services Composition

Dynamic composition of web services is a promising approach and at the same time a challenging research area for the dissemination of service-oriented 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 enable the computation of relevant and most suitable 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.

Towards runtime discovery, selection and composition of semantic services

Service-orientation is gaining momentum in distributed software applications, mainly because it facilitates interoperability and allows application designers to abstract from underlying implementation technologies. Service composition has been acknowledged as a promising approach to create composite services that are capable of supporting service user needs, possibly by personalising the service delivery through the use of context information or user preferences. In this paper we discuss the challenges of automatic service composition, and present DynamiCoS, which is a novel framework that aims at supporting service composition on-demand and at runtime for the benefit of service end-users. We define the DynamiCoS framework based on a service composition life-cycle. Framework mechanisms are introduced to tackle each of the phases and requirements of this life-cycle. Semantic services are used in our framework to enable reasoning on the service requests issued by end-users, making it possible to automate service discovery, selection and composition. We validate our framework with a prototype that we have built in order to experiment with the mechanisms we have designed. The prototype was evaluated in a testing environment using some use case scenarios. The results of our evaluation give evidences of the feasibility of our approach to support runtime service composition. We also show the benefits of semantic-based frameworks for service composition, particularly for end-users who will be able to have more control on the service composition process.

Enterprise interoperability with SOA: a survey of service composition approaches

Service-oriented architecture (SOA) claims to facilitate the construction of flexible and loosely coupled business applications, and therefore is seen as an enabling factor for enterprise interoperability. The concept of service, which is central to SOA, is very convenient to address the matching of needs and capabilities in enterprise collaborations. In order to satisfy more demanding needs or to rapidly adapt to changing needs it is possible to perform service composition in order to combine the capabilities provided through several available services. This paper presents a survey on recent approaches for service composition. To perform this study a conceptual framework for service composition is proposed. This framework allows studying how different approaches deal with the service composition life-cycle and provides basic guidelines for their analysis, evaluation and comparison. The proposed framework is used to analyse five representative service composition approaches.

Towards a Goal-Based Service Framework for Dynamic Service Discovery and Composition

Service-Oriented Computing allows new applications to be developed by using and/or combining services offered by different providers. Service discovery and composition are performed aiming to comply with the client’s request in terms of functionality and expected outcome. In this paper we present a framework for dynamic service discovery and composition. This framework is based on goals and tasks as the means to represent the client’s expected outcome and functionality, respectively. The framework encompasses a goal-based service ontology, a set of domain and task ontologies and a supporting service platform with a service matching and composition algorithm. The client informs the platform about the goal to be fulfilled. The platform’s matching algorithm searches in the repository for services that can fulfill the client’s goal. Moreover, the platform gathers client’s contextual information to use as inputs for the services and thus, reduce the need for client interaction. If no single service is able to fulfill the user’s goal, a service composition is then performed.

GSO: Designing a well-founded service ontology to support dynamic service discovery and composition

A pragmatic and straightforward approach to semantic service discovery is to match inputs and outputs of user requests with the input and output requirements of registered service descriptions. This approach can be extended by using pre-conditions, effects and semantic annotations (meta-data) in an attempt to increase discovery accuracy. While on one hand these additions help improve discovery accuracy, on the other hand complexity is added as service users need to add more information elements to their service requests. In this paper we present an approach that aims at facilitating the representation of service requests by service users, without loss of accuracy. We introduce a Goal-Based Service Framework (GSF) that uses the concept of goal as an abstraction to represent service requests. This paper presents the core concepts and relations of the Goal-Based Service Ontology (GSO), which is a fundamental component of the GSF, and discusses how the framework supports semantic service discovery and composition. GSO provides a set of primitives and relations between goals, tasks and services. These primitives allow a user to represent its goals, and a supporting platform to discover or compose services that fulfil them.

On the support of dynamic service composition at runtime

Network-based software application services are receiving a lot of attention in recent years, as observed in developments as Internet of Services, Software as a Service and Cloud Computing. Aservice-oriented computing ecosystem is being created where the end-user is having an increasingly more active role in the service creation process. However, supporting end-users in the creation of a service, at runtime, is a difficult undertaking. Users are heterogeneous, have different requirements, preferences and knowledge. Furthermore, and since we cannot assume that all users are technical experts, we conclude that highly abstract mechanisms should be available to support the service creation process. To tackle these issues and provide end-users with personalised service delivery, we claim that runtime automated service composition mechanisms are required. In this paper we present the DynamiCoS framework, which aims at supporting the different phases required to provide users with automatic service discovery, selection and composition process. In this paper we also present the developed prototype and its evaluation.

A Framework for the Evaluation of Semantics-Based Service Composition Approaches

The benefits of service composition are being largely acknowledged in the literature nowadays. However, as the amount of available services increases, it becomes difficult to manage, discover, select and compose them, so that automation is required in these processes. This can be achieved by using semantic information represented in ontologies. Currently there are many different approaches that support semantics-based service composition. However, still little effort has been spent on creating a common methodology to evaluate and compare such approaches. In this paper we present our initial ideas to create an evaluation framework for semantics-based service composition approaches. We use a collection of existing services, and define a set of evaluation metrics, confusion matrix-based and time-based. Furthermore, we present how composition evaluation scenarios are generated from the collection of services and specify the strategy to be used in the evaluation process. We demonstrate the proposed framework through an example. Currently there are mechanisms and initiatives to address the evaluation of the semantics-based service discovery and matchmaking approaches. However, still few efforts have been spent on the creation of comprehensive evaluation mechanisms for semantics-based service composition approaches.

A-DynamiCoS: A Flexible Framework for User-centric Service Composition

Service composition has been acknowledged as a promising approach to create new (composite) services that are capable of supporting multiple needs of service users. Service composition has been used quite extensively to support complex but relatively stable enterprise processes. More recently, service composition is also being applied to support the personalization of services delivered to human end-users. In these situations, the aim is to create service compositions on demand, at runtime, that match the specific requirements of each individual end-user, characterizing user-centric dynamic service composition processes. The most common approach to dynamic service composition aims at creating service compositions that once obtained must be deployed and executed by some sort of orchestration engine. In this approach, the service composition life-cycle is fixed, with serious limitations to its applicability in more realistic situations. This paper presents the A-DynamiCoS framework, which applies a novel approach to user-centric service composition by providing flexible support to the different activities of the service composition life-cycle. In this approach, components that perform service discovery, composition and execution activities are orchestrated, breaking the traditional rigid life-cycle (discover, then compose, then deploy and finally execute). We claim that dynamic orchestration of service composition activities enables true user-centric service delivery. This paper motivates and justifies the development of A-DynamiCoS, and presents use cases that demonstrate our claims.

Model for Trans-sector Digital Interoperability

Interoperability refers to the ability of two or more systems or components to exchange information and to use the information that has been exchanged. The importance of interoperability has grown together with the adoption of Digital Information Networks (DINs). DINs refer to information networks supported by telecommunication infrastructures and terminated by microprocessors. With an upcoming interest in services science and transsector business models, a stronger driver arises to further break the interoperability barriers across sectors. In this paper, we propose a novel model to address trans-sector digital interoperability, which by definition involves interoperability across different economic sectors connected by DINs. Particularly, we specify how a well known interoperability framework, the ATHENA framework, should be adapted for the economic sector plane. Based on data from the Eurostat survey on ICT usage and e-Commerce in enterprises, we illustrate how conclusions about trans-sector interoperability can be extracted and technological implications can be derived.

On the Design of User-Centric Supporting Service Composition Environments

In a user-centric service creation process, users should drive the service creation, in which services can be composed out of existing services. However, the creation is expected to take place also at runtime and possibly be performed by non-technical users. These users require support in the composition process, since they cannot deal with all the technical details of service composition. Furthermore, users have different characteristics and properties. In this paper we propose a classification of users in terms of their application domain and technical knowledge in order to identify different types of users and their requirements in the service composition process. These requirements can be used to design and build suitable supporting composition environments. Although our classification of users may seem trivial at first sight, it is quite essential for identifying users requirements and derive the appropriate supporting environment. Nowadays most of the approaches are technology-driven rather than user-oriented. We argue that only by taking the user into account a truly user-centric service creation and delivery can be achieved.