F. De Paoli

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.

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.

Design of quality-based composite web services

One of the key factors for successful SOC-based systems is the ability to assure the achievement of Quality of Services. The knowledge and the enforcement of the Quality of Services allows for the definition of agreements that are the basis for any business process. In this paper we discuss a method for the evaluation of qualities associated with services. This method is based on a set of quality evaluation rules that state the relations between Web services quality dimensions and process structure. The method is part of a design methodology that addresses quality issues along the service life-cycle. A case study in the e-placement field is presented to illustrate a practical use of the approach.

On the complementary nature of event-driven and time-driven models

Abstract Event-driven and time-driven models exhibit a complementary nature, in the sense that they reflect the nature of the contrasting requirements that any real-time system must meet - i.e., performing actions “as soon as possible” or “at the right time”. Even if each of the models is sufficient to model a system, they should be intermixed to improve the expressiveness. This can be achieved by assuming one model as the primitive, and implementing the other on top of it. The paper introduces the rationale for choosing the time-driven model as the primitive, and discusses why this approach is possibly the most suitable for a wide range of control applications. In conclusion, a unifying model, based on the distinction between the atomic actions performed by reactive agents, the control performed by a time-driven control machine, and the planning performed by an event-driven planning machine, is introduced.

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.

Requirements for a layered software architecture supporting cooperative multi-user interaction

Layered interactive systems lend themselves to be adapted for cooperation if inter-layer communication is charged to separated connectors. Point-to-point connectors can be replaced with cooperative connectors multiplexing and demultiplexing I/O between a particular layer and multiple instances of the next lower one. For this technique to be most effective, some general guidelines should be followed that support the design of good quality software where discrimination between heterogeneous functionality at the architectural level allows multiple interacting users to exploit different system features based on their role in the cooperation. This provides a sound basis for augmenting collaboration-transparent layered systems with powerful collaboration support (e.g. complex coordination policies) yet preserving separation of concerns between applicative and cooperative functionality. The paper discusses these issues both in general and with reference to their application within the CSDL framework for cooperative systems design.

Architectural abstractions and time modelling in HyperReal

This paper describes the foundation of the HyperReal project. It is centred on the definition of architectural abstractions that permit designing modular RT systems. Basic components are reactive agents manipulating data and connectors supporting interactions among agents. Such components are not aware of the system configuration nor of the control strategy, which are managed by a configurator and by a controller respectively. The controller relies on a time-driven model of control, and separates the definition of plans from the dispatching of the actions they define. Plans are associated with virtual clocks which support the explicit management of time. The architectural abstractions allow a designer to fully control the temporal behaviour of the system and to reuse components under different application-oriented control models.

An adaptive middleware to support context-aware knowledge sharing

Due to the diffusion of ubiquitous computing environments, the need for adaptive applications to effectively support knowledge sharing, and improve context awareness without interfering with habitual work practices has gained importance. This paper presents the design of an application architecture that exploits an ontology-based knowledge management framework and a reflective middleware to support multi-channel applications. The development of the middleware is carried on in parallel with the development of a real application, SWIRLS, that aims to support the work in a hospital setting. SWIRLS is a case study with real technology and organizational problems that involves innovative devices, seamless interaction via different channels and domain-dependent knowledge management issues.

A service re-design methodology for multi-channel adaptation

Many available services have been designed for a single-channel world, Web and Internet typically. In a real world scenario, an ever-growing number of users take advantage of different kinds of communication channels and devices. In this paper, we propose a methodology to formalize the re-design process of these services to support multi-channel access in different contexts. The methodology considers the channel characteristics, the location of users and the context of use to characterize the new services. It has been tested in a case study: the Italian National Project of Identification and Registration of Bovine Animals.