Flavio De Paoli

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.

A support system to COTS-based software development for business services

The work described in this paper deals with the problem of selecting, configuring, integrating and deploying COTS components to deliver tailored software systems. Since formal and precise description of components is not usually available, a reasonable approach is to augment the available documentation with the informal knowledge derived by practices and experience of experts. The development of a knowledge-based system is a way to organize this empirical knowledge and deliver a tool that can support software designers in the tough goal of COTS-based development.

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.

A framework for self-descriptive RESTful services

REST principles define services as resources that can be manipulated by a set of well-known methods. The same approach is suitable to define service descriptions as resources. In this paper, we try to unify the two concepts (services and their descriptions) by proposing a set of best practices to build self-descriptive RESTful services accessible by both humans and machines. Moreover, to make those practices usable with little manual effort, we provide a software framework that extracts compliant descriptions from documents published on the Web, and makes them available to clients as resources.

Weakly augmented reality: observing and designing the work-place of creative designers

In this paper we distinguish between two spatially oriented system design paradigms: weak and strong augmented reality. The weak augmented reality paradigm is then applied in the design of a system supporting co-operation and knowledge creation within a design centre. The system has been designed on the hints we got from two subsequent ethnographies of the work practice of creative designers. Since the design centre moved to a new location between our two sets of observations, we clearly focused our attention on the impact that space arrangements had on the practice of its members. The comparison between the two settings in terms of layout, ICT equipment, changes occurred in the practices and attitudes of the designers throughout these years, lead us to design a collaborative environment weakly augmenting the place where designers are working.

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.

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).

Advanced Non-functional Property Evaluation of Web Services

Web service evaluation is a phase in Web service selection where discovered Web services are evaluated with respect to user requests, which means that the non functional properties (NFPs) offered by Web services are compared with the non functional properties requested by users. NFPs cover Quality of Service (QoS) aspects, but also other business-related properties, such as pricing, and properties not directly related to the service functionalities. The fact that users and providers can express their NFPs in very flexible ways makes the management of NFP a very complex task. The Policy Centered Meta-model (PCM) is a semantic-oriented model for sophisticated NFP descriptions that can be exploited to support Web service evaluation. In this paper, we propose a novel approach based on Hierarchical Constraint Logic Programming to handle PCM-based NFP descriptions along the Web service evaluation phase.