Babak Esfandiari

Management applications of the web service offerings language (WSOL)

We discuss Web Service Management (WSM) and Web Service Composition Management (WSCM) applications of the Web Service Offerings Language (WSOL) and how the language supports these applications. WSOL is a language for the formal specification of classes of service, various constraints (functional constraints, Quality of Service QoS, and access rights), and management statements (prices, monetary penalties, and management responsibilities) for Web Services. Describing a Web Service in WSOL, in addition to the Web Services Description Language, enables monitoring, metering, accounting, and management of Web Services. Metering of QoS metrics and evaluation of constraints can be the responsibility of the provider Web Service, the consumer, and/or one or more mutually trusted third parties (SOAP intermediaries or probes). Further, manipulation (switching, deactivation, reactivation, deletion, or creation) of classes of service can be used for dynamic (run-time) adaptation and management of Web Service compositions. To demonstrate the usefulness of WSOL for WSM and WSCM, we have developed a corresponding management infrastructure, the Web Service Offerings Infrastructure (WSOI). WSOI enables monitoring of WSOL-enabled Web Services and dynamic manipulation of their classes of service.

On Requirements for Ontologies in Management of Web Services

Formal specification of various constraints, including quality of service (QoS) and price, is very important for successful dynamic (i.e., runtime) composition of Web Services. For specification of these constraints, it is important to formally define QoS metrics, measurement units, and currency units used. Ontologies provide a mechanism for such formal definition. In this paper we discuss some requirements for ontologies that can be used in representing QoS constraints and in management of Web Services, with special focus on QoS metrics, measurement units, and currency units. Particularly, we emphasize the need for the formal representation of dependencies and relationships between QoS metrics, even when such information seems redundant. Our study of existing ontologies showed that they need further work to satisfy our requirements. We also state the need for independent, third-party Web Services for ontological translations between different QoS metrics, measurement units, and currencies.

Web Service Offerings Infrastructure (WSOI) - a management infrastructure for XML Web services

Our Web Service Offerings Language (WSOL) enables formal specification of important management information - classes of service (modeled as service offerings), various types of constraint (functional, QoS, access rights), and management statements (e.g., prices, penalties, and management responsibilities) - for XML (Extensible Markup Language) Web services. To demonstrate the usefulness of WSOL for the management of Web services and their compositions, we have developed a corresponding management infrastructure, the Web Service Offerings Infrastructure (WSOI). WSOI enables monitoring and accounting of WSOL service offerings and their dynamic manipulation. To support monitoring of WSOL service offerings, we have extended the Apache Axis open-source SOAP engine with WSOI-specific modules, data structures, and management ports. To support dynamic manipulation of WSOL service offerings, we have developed appropriate algorithms, protocols, and management port types and built into WSOI modules and data structures for their implementation. Apart from provisioning of WSOL-enabled Web services, we are using WSOI to perform experiments comparing dynamic manipulation of WSOL service offerings and alternatives.

Towards a classification of web service feature interactions

The rapid introduction of new web services into a dynamic business environment can lead to undesirable interactions that negatively affect service quality and user satisfaction. In previous work, we have demonstrated how such interactions between web services can be modeled as feature interactions. In this paper, we outline a classification of web service feature interactions. The goals of this classification are to understand the scope of the feature interaction problem in the web services domain, and to propose a benchmark against which to assess the coverage of solutions to this problem. As there is no standard set of web services that one could use as examples, we illustrate the interactions using a fictitious e-commerce scenario.

On Feature Interactions Among Web Services

Web Services promise to allow businesses to adapt rapidly to changes in the business environment and to the needs of customers. However, the rapid introduction of new services paired with the dynamicity of the business environment also leads to undesirable interactions that negatively impact service quality and user satisfaction. In this paper, we propose an approach for modeling such undesirable interactions as feature interactions. As each functional feature ultimately is motivated by non-functional requirements, we make an explicit distinction between functional and non-functional features. We then describe our approach for detecting and resolving feature interactions among Web Services. The approach is based on goal-oriented analysis and scenario modeling. It allows us to reason about feature interactions in terms of goal conflicts and feature deployment. Three case studies illustrate the approach. The paper concludes with a discussion of our findings and an outlook on future research.

A Hybrid Approach to Operating System Discovery using Answer Set Programming

The goal of operating system (OS) discovery is to learn which OS is running on a distant computer. There are two main strategies for OS discovery: active and passive. Each of them has advantages as well as drawbacks. This paper discusses how answer set programming, a new logic programming paradigm, can be used to address, in a simple and elegant way, the problem of operating system discovery in computer networks by logically specifying the problem and providing solutions through automated reasoning. As a result of using such a knowledge representation framework, it is possible to unify the active and the passive methods to OS discovery in a single hybrid approach that has the advantages of both strategies while being much more versatile. Moreover, this paper presents a proof of concept prototype for hybrid operating system discovery.

Towards a Web service composition management framework

We suggest that the composition of Web services is an activity that needs to be managed, and that Web service composition management is distinct from the management of individual Web services. We describe a set of requirements to help make this distinction. The four main groups of these requirements are: service discovery, service selection and contract formation, composition verification, composition management. Then, we discuss architectural alternatives (centralized, federated, and peer-to-peer) for a Web service composition management framework.

On feature interactions among Web services

Web services promise to allow businesses to adapt rapidly to changes in the business environment, and the needs of different customers. However, the rapid introduction of new services paired with the dynamicity of the business environment also leads to undesirable interactions that negatively impact service quality and user satisfaction. In this paper, we propose an approach for modeling such undesirable interactions as feature interactions. Our approach for detecting interactions is based on goal-oriented analysis and scenario modeling. It allows us to reason about feature interactions in terms of goal conflicts, and feature deployment. Two case studies illustrate the approach. The paper concludes with a discussion, and an outlook on future research.

Defining and investigating device comfort

Device Comfort is a concept that uses an enhanced notion of trust to allow a personal (likely mobile) device to better reason about the state of interactions and actions between it, its owner, and the environment. This includes allowing a better understanding of how to manage information in fine-grained context as well as addressing the personal security of the user. To do this, it forms a unique relationship with the user, focusing on the devices judgment of user in context. This paper introduces and defines Device Comfort, including an examination of what makes up the comfort of a device in terms of trust and other considerations, and discusses the uses of such an approach. It also presents some ongoing developmental work in the concept, and an initial formal model of Device Comfort, its makeup and behaviour.

Management of compositions of e- and m-business Web services with multiple classes of service

The concept of a Web service, as defined by W3C (World Wide Web Consortium), represents a distributed component using XML messaging. Compositions of Web services are increasingly used to create new IT capabilities fast and flexibly, in an ad hoc manner. This work extends the W3C concept of a Web service in two ways. First, we enable a Web service to offer several variations of service and QoS. In other words, we add the concept of classes of service for Web services. This widens the usability of a particular Web service. Second, we explore dynamic (i.e., run-time) adaptation and management based on the manipulation of classes of service. Our dynamic adaptation mechanisms include switching, deactivation/reactivation, and creation of classes of service. Management and dynamic adaptation of Web service compositions further improve the overall flexibility and adaptability of IT systems using Web services.