Marco Comerio

A Meta-model for Non-functional Property Descriptions of Web Services

In this paper we propose a meta-model for nonfunctional property descriptions targeted to support the selection of Web Services. The approach is based on the explicit distinction between NFP offered by providers and requested by users, on the concept of policy that aggregates NFP descriptions into single entities with an applicability condition, and finally on a set of constraint operators, which is particularly relevant for NFP requests. The semantic meta-model embracing the above perspective is defined by a BNF syntax whose semantics is formalized by an ontology. The ontology has been formalized in OWL-DL and WSML to provide for logical syntax. The logic upon which the meta-model supports NFP-based selection is discussed in the paper.

Effective and Flexible NFP-Based Ranking of Web Services

Service discovery is a key activity to actually identify the Web services (WSs) to be invoked and composed. Since it is likely that more than one service fulfill a set of user requirements, some ranking mechanisms based on non-functional properties (NFPs) are needed to support automatic or semi-automatic selection. This paper introduces an approach to NFP-based ranking of WSs providing support for semantic mediation, consideration of expressive NFP descriptions both on provider and client side, and novel matching functions for handling either quantitative or qualitative NFPs. The approach has been implemented in a ranker that integrates reasoning techniques with algorithmic ones in order to overcome current and intrinsic limitations of semantic Web technologies and to provide algorithmic techniques with more flexibility. Moreover, to the best of our knowledge, this paper presents the first experimental results related to NFP-based ranking of WSs considering a significant number of expressive NFP descriptions, showing the effectiveness of the approach.

Evaluating Contract Compatibility for Service Composition in the SeCO2 Framework

Recently, the Software-as-a-Service (SaaS) model has been increasingly supported, becoming a major part of the new emerging cloud computing paradigms. Although SaaS exists in different forms, supporting and providing SaaS developed based Web services has attracted a large effort from industries and academics because this form of SaaS allows software to be easily composed and integrated to offer new services for customers. Even though various service composition techniques, based on functional and non-functional parameters, have been proposed, the issue of service contract compatibility has been neglected. This issue is of paramount importance in the Web services-based SaaS model because services are provided by different providers, associated with different contracts which are defined by different specifications. This paper proposes techniques for supporting service composers to deal with the heterogeneity of service contracts in service composition. We describe a novel approach for modeling and mapping different service contract specifications, and a set of techniques for evaluating service contract compatibility. Our techniques consider contract terms associated with data and control flows, as well as composition patterns. Illustrating scenarios are proposed to demonstrate the efficiency of our techniques.

GLUE2: A Web Service Discovery Engine with Non-Functional Properties

The increasing availability of Web services asked for investigating ways to automate the discovery process. Discovery processes enhanced with semantics can be recognize to be general, but often they lack the flexibility needed in specific domains. In this paper, we propose the flexible architecture of the discovery engine Glue2, which comes with a powerful set of discovery components (for functional matching, non-functional matching, data fetching, etc.) that can be executed in different order as required by specific execution workflows.

NFP-aware Semantic Web Services Selection

The discovery of a semantic web service (SWS) is the act of locating a machine-processable description of a SWS-related resource that may have been previously unknown and that meets certain functional criteria. The increasing availability of services that offer similar functionalities requires the discovery process to be enhanced with a selection phase that considers non-functional properties (NFPs) of services. This paper proposes a model to describe these properties and a novel approach to service selection. Our approach is based on the design of matching rules by means of mediators defined by sets of rules stating the condition for successful matches. These rules are based on the ontological description of objects representing NFPs that are required and offered. In particular, we define a set of rule schemas to support mediation and matching for a class of user-defined NFP-constraints clustered according to specified constraint operators. Rules support matching for both qualitative and quantitative non-functional properties.

Data contracts for cloud-based data marketplaces

Currently, rich and diverse data types have been increasingly provided using the data-as-a-service (DaaS) model, a form of cloud computing services and the core element of data marketplaces. This facilitates the on-the-fly data composition and utilisation for several dataintensive applications in e-science and business domains. However, data offered by DaaS are constrained by several data concerns that, if not automatically being reasoned properly, will lead to a wrong way of using them. In this paper, we support the view that data concerns should be explicitly modelled and specified in data contracts to support concern-aware data selection and utilisation. We perform a detailed analysis of current techniques for data contracts in the cloud. Instead of relying on a specific representation of data contracts, we introduce an abstract model for data contracts that can be used to build different types of data contracts for specific types of data. Based on the abstract model, we propose several techniques for evaluating data contracts that can be integrated into data service selection and composition frameworks. We also illustrate our approach with some real-world scenarios and show how data contracts can be integrated into data agreement exchange services in the cloud.

On Analyzing and Developing Data Contracts in Cloud-Based Data Marketplaces

Currently, rich and diverse data types have been increasingly provided using the Data-as-a-Service (DaaS) model, a form of cloud computing services. However, data offered by DaaS are constrained by several data concerns that, if not automatically being reasoned properly, will lead to a wrong way of using them. In this paper, we support the assumption that data concerns should be explicitly modeled and specified in data contracts to support concern-aware data selection and utilization. Instead of relying on a specific definition of data contracts, we analyze contemporary data contracts and we present an abstract model for data contracts. Based on the abstract model, we propose several techniques for evaluating data contracts that can be integrated into data service selection and composition frameworks. We also illustrate our approach with some real world scenarios.

Distributed matchmaking and ranking of Web APIs exploiting descriptions from Web sources

Semantic Web service (SWS) technology promotes the definition of Web service descriptions with semantic annotations to better support Web service selection. Unfortunately, SWS descriptions tend to be huge and complex and their evaluation is characterized by limited scalability. The result is that very few descriptions exist in reality. Web service providers prefer to publish functional and non-functional properties (NFPs) of their RESTful services, also called Web APIs, by means of structured data (e.g., XML, JSON) or textual descriptions. In this paper we define an effective and efficient distributed matchmaking for Web API ranking based on: (i) techniques for the extraction of property descriptions from heterogeneous, dynamic and distributed information on the Web and (ii) a distributed architecture to improve the performance of the Web API matchmaking processes.

WSMoD: A Methodology for QoS-Based Web Services Design

Web services are increasingly used as an effective means to create and streamline processes and collaborations among governments, businesses, and citizens. As the number of available Web services is steadily increasing, there is a growing interest in providing methodologies that address the design of Web services according to specific qualities of service (QoS) rather than functional descriptions only. In this paper, we present WSMoD (Web Services MOdeling Design), a methodology that explicitly addresses this issue. Furthermore, we exploit general knowledge available on services, expressed by ontologies describing services, their qualities, and the context of use, to help the designer in expressing service requirements. Ontologies are used to acquire knowledge among the entities involved in service design and to check the consistency of the Web service. The discussion of a QoS-based Web service design within a real case study bears evidence of the potentials of WSMoD.

An Approach to Non-functional Property Evaluation of Web Services

Web service evaluation is a phase of the Web service selection in which discovered Web services are evaluated with respect to user request, which means that the non functional properties (NFPs) offered by Web services are compared with the non functional properties requested by users. The fact that users and providers can express their NFPs in very flexible ways makes the management of NFPs a very complex task. In this paper we propose a computing-oriented description of NFPs and a novel approach to NFP-based service evaluation based on Hierarchical Constraint Logic Programming. This proposal extends our previous work on Policy Centered Meta-model (PCM).