George N. Prezerakos

Context-aware service engineering: A survey

Context constitutes an essential part of service behaviour, especially when interaction with end-users is involved. As observed from the literature, context handling in service engineering has been during recent years a field of intense research, which has produced several interesting approaches. In this paper, we present research efforts that attempt mainly to decouple context handling from the service logic. We enumerate all context management categories, but focus on the most appropriate for service engineering, namely source code level, model-driven and message interception, taking also into account the fact that these have not been dealt with in detail in other surveys. A representative example is used to illustrate more precisely how these approaches can be used. Finally, all three categories are compared based on a number of criteria.

Model-driven development of composite context-aware web applications

Context-awareness constitutes an essential aspect of services, especially when interaction with end-users is involved. In this paper a solution for the context-aware development of web applications consisting of web services is presented. The methodology proposes a model based approach and advocates in favour of a complete separation of the web application functionality from the context adaptation at all development phases (analysis, design, implementation). In essence, context adaptation takes place on top of and is transparent to the web application business functionality. Starting from UML diagrams of independent web services and respective UML context models, our approach can produce a functional composite context-aware application. At execution level this independence is maintained through an adaptation framework based on message interception.

Model-driven Composition of Context-aware Web Services Using ContextUML and Aspects

Service oriented architectures (SOAs) are constantly gaining ground for the provision of business to business as well as user-centric services, mainly in the form of Web services technology. SOAs enable service providers to design and deploy new,composite service offerings out of existing component services. In order to match end-user expectations with respect to personalization and ease of use, these services should be designed in a manner that allows them to exhibit a certain level of context-awareness which is a basic element towards a richer end-user experience. However, in the majority of such services, context-handling is still tightly coupled with the core functionality of the service, resulting in a design which is difficult to implement and maintain. The paper proposes the decoupling of core service logic from context-related functionality by adopting a model-driven approach based on a modified version of the ContextUML metamodel. Core service logic and context handling are treated as separate concerns at the modeling level as well as in the resulting source code where aspect oriented programming (AOP) encapsulates context-dependent behavior in discrete code modules. The design of a restaurant finder service is used to portray the modified ContextUML metamodel and the service modeling process which is covered in full. Respective code snippets belonging to the executable version of the service (part of work in progress) are also provided, illustrating the transition from model to code and the resulting separation of concerns.

Service Composition: State of the art and future challenges

Service discovery and service composition constitute challenging tasks of service provisioning. Service composition is especially gaining on importance, as it can produce new composite services with features not present in the individual services. Many methods have been proposed over the years to address these issues. Simple Mobile Services (SMS) is a project aiming at creating innovative tools that will introduce a new class of mobile services enabling individuals and small businesses to become service providers. In this paper an attempt is made to present an overview of all existing techniques on service composition and examine them in the context of SMS. The enumeration of the techniques is complete and focuses mostly on recent approaches. Moreover, service composition is discussed under the prism of mass service provisioning by mobile operators where some techniques currently seem to be more suitable than others.

INSIGNIA: a pan European trial for the intelligent broadband network architecture

This article summarizes the work carried out within the ACTS project INSIGNIA, which is targeted at the provision of interactive multimedia services through IN and B-ISDN integration. The basic concepts regarding the integrated approach are discussed with emphasis on the functional architecture. This discussion is followed by a presentation of IN multimedia services which were created based on these principles. An overview of the real-life trials which were conducted on a pan-European basis in order to evaluate the INSIGNIA services is also given. The results of this evaluation are examined from a variety of viewpoints, including functional architecture, user and network equipment, service logic programs and applications, as well as user acceptance and network performance.

SMS: Simplifying Mobile Services - for Users and Service Providers

To date, mobile services have failed to match the explosive growth of the World Wide Web. This, we argue, is because current services are difficult to use, design and deploy. In this paper we describe a concept for a new class of services, addressing these issues. We call these services Simple Mobile Services (SMS). SMS will be simple for users to find, use, and trust; similarly they will be simple for providers to develop and deploy. Like the Web, they will provide technology and operator-independent end-to-end connectivity. But unlike conventional Web-based services they will target specific locations of interest to specific classes of mobile user with specific needs. We propose a design methodology and a set of related tools for the creation of SMS - based on the Model Driven Architecture (MDA) approach. We show how this methodology can support the design and deployment of SMS by service providers with limited technical expertise.

A Proxy for Privacy: the Discreet Box

The issue of user privacy is constantly brought to the spotlight since an ever increasing number of online services collects and processes personal information from users, in the context of personalized service provision. Although technology makes the collection of data easy, their protection against abuse is left to data protection legislation. However, the privacy requirements, other than being general and abstract terms to be regarded as legislature issues, should be brought down in the technological reality and carefully accounted for in devising technical solutions. In order to limit the disclosure and avoid the misuse of personal data, this paper discusses an architectural proposal for a middleware system that will enforce protection of user privacy through technical means. This goal is facilitated by a combination of a policy framework, a sensible interpretation of regulations into policies and the introduction of a privacy broker, named the discreet box.

Modeling Context Information for Realizing Simple Mobile Services

The emerging technology of mobile services is gaining on importance nowadays and various applications are being developed. Context-awareness constitutes an essential part of mobile services, as it can boost the provision of new personalized services (e.g. location based services). In this paper, the concept of a UML-based context model for the simple mobile services (SMS) project is presented. The SMS context model focuses on modeling context information in a structured and comprehensible way in order to facilitate the development, provision and operation of context-aware mobile services. Its three-level approach (meta, model and instance) offers different levels of abstraction and can be used as a basis for transforming the resulting model to various implementation languages.

Wholesale provision of broadband services: alternative pricing strategies and associated policies

Purpose – The paper aims to explore the “build or lease” dilemma that a new operator faces when it plans to enter a liberalized telecom market. The “build” decision requires the operator to invest in new network infrastructure. The “lease” part involves obtaining access to the subscriber by leasing the access part of the network via local loop unbundling (LLU) and/or by implementing wholesale broadband access (WBA) (also known as bitstream access). Which are the factors that an operator should take into account when it designs a broadband strategy based on LLU and/or WBA? Are there regulatory measures that can affect the outcome of such a strategy? The paper aims to provide specific answers to both questions.Design/methodology/approach – Initially the paper establishes the case that LLU as well as WBA can indeed be considered as a useful instrument during the initial stages of broadband development. Consequently, the paper explores the “build or lease” dilemma by using a cost model created from actual mar...

Efficient resource allocation with service guarantees in passive optical networks

Feature Issue on Passive Optical Network Architectures and TechnologiesWe propose and evaluate a resource allocation scheme for time-division multiplexing passive optical networks (PONs), which supports multiple service classes; dynamic bandwidth allocation for services with varying (in time) capacity demand; and bounded quality of service parameters for services with real-time requirements. Although several algorithms have been proposed in the literature considering several of the above objectives in isolation, our work focuses on the fundamental problem of trading-off between PON upstream channel utilization and strict delay and jitter bounds when supporting a dynamically changing mix of services with different requirements.