Philipp Bostan

A Practical Approach to Web Service Discovery and Retrieval

One of the fundamental pillars of the Web service vision is a brokerage system that enables services to be published to a searchable repository and later retrieved by potential users. This is the basic motivation for the UDDI standard, one of the three standards underpinning current Web service technology. However, this aspect of the technology has been the least successful, and the few Web sites that today attempt to provide a Web service brokerage facility do so using a simple cataloguing approach rather than UDDI. In this paper we analyze why the brokerage aspect of the Web service vision has proven so difficult to realize in practice and outline the technical difficulties involved in setting up and maintaining useful repositories of Web services. We then describe a pragmatic approach to web service brokerage based on automated indexing and discuss the required technological foundations. We also suggest some ideas for improving the existing standards to better support this approach and Web service searching in general.

Orthographic Software Modeling: A Practical Approach to View-Based Development

Although they are significantly different in how they decompose and conceptualize software systems, one thing that all advanced software engineering paradigms have in common is that they increase the number of different views involved in visualizing a system. Managing these different views can be challenging even when a paradigm is used independently, but when they are used together the number of views and inter-dependencies quickly becomes overwhelming. In this paper we present a novel approach for organizing and generating the different views used in advanced software engineering methods that we call Orthographic Software Modeling (OSM). This provides a simple metaphor for integrating different development paradigms and for leveraging domain specific languages in software engineering. Development environments that support OSM essentially raise the level of abstraction at which developers interact with their tools by hiding the idiosyncrasies of specific editors, storage choices and artifact organization policies. The overall benefit is to significantly simplify the use of advanced software engineering methods.

Context-aware User Interface Framework for Mobile Applications

Mobile devices available today are very heterogenous with regard to their display and input capabilities and used software platform configurations. This leads to a complex development process for applications which have to target a wide range of devices. Adapting the interface of an application to the current context of the user adds another burden to developers, while improving the user experience. Therefore we developed an XUL-based User Interface Framework which eases the development of mobile applications by separating the UI adaption from the application logic and offering portability to different Java ME platform configurations. Using this framework the user interface (UI) adapts itself automatically on context-changes and changes to different screen resolutions or orientations without increasing code complexity for the developers.

Towards a Client-Oriented Model of Types and States in Service-Oriented Development

As its success has demonstrated, the principles of service-oriented architectures yield significant benefits for the integration, maintenance and administration of complex enterprise computing systems. However, they are primarily oriented towards the needs of server-side system integrators rather than the developers of client applications and business processes. In particular, the absence of the notion of types, in the sense of abstract data types and object-oriented programming, limits the way in which client and process developers can access resources in a service-oriented architecture and leverage reusable assets. This is additionally aggravated by the confusion surrounding the notion of state and the question of whether services should in general be stateful or stateless. In this paper we address these problems by introducing a client-oriented model of Web services in service-oriented development that provides a flexible notion of types and instances, and distinguishes between client-oriented and implementation-oriented notions of service state. We also introduce the concept of congregation as a new role in service-oriented development designed to support the new type model and discuss how it can be implemented in the light of the proposed state model using Web services as the underlying technology.

Interaction Styles for Service Discovery in Mobile Business Applications

As the power of mobile devices continues to grow, and the range of resources accessible via wireless networks expands, there is an increasing need to offer services to users in a customized way, based on their immediate desires and context. At the same time, to construct such applications in a cost-effective and reusable way, there is also a growing pressure on mobile application developers to structure their systems in terms of a service-oriented architecture. However, these two goals are not always compatible. In this paper we present a new set of architectural components and principles which allow context-sensitive, mobile business applications to be assembled in highly flexible and reuse-oriented way based on the principles of SOA. We present the four main configuration patterns and interaction styles which this architecture supports and evaluate their pros and cons from the perspective of different infrastructure and usability issues such as bandwidth usage, latency needs, pricing and, privacy. Finally, we discuss which configuration to use in which circumstances

Foundational MDA Patterns for Service-Oriented Computing

As the foundation of EDI, B2C and B2B, distributed comput- ing is a key enabler for todays enterprises and will become even more important with the advent of cloud computing on the one hand and an ever more agile work organization on the other hand. Whilst the rapid evolution of distributed computing technologies in the last three decades has delivered a rich set of platforms and paradigms for building robust enterprise systems, it has also left a legacy of unresolved problems includ- ing fundamental inconsistencies between the concepts of the two leading distributed computing paradigms, i.e., distributed object computing and service-oriented architecture. Equally important, there is a growing need to lower the complexities and barriers involved in developing client appli- cations, which range from large scale business applications and business processes to laptop programs and small apps on mobile devices. In this article, we present a unified conceptual framework for service-oriented computing based on the proven MDA (Model Driven Architecture) ter- minology stack. With the conceptual framework we consolidate, and give semantics to, core concepts of service-oriented computing and provide a set of foundational model transformation patterns that map between the presented concepts and further clarify practical service-oriented comput- ing scenarios. Finally, we show how the developed framework perfectly fits to the OSM (Orthographical Software Modeling) approach.

A Unified Conceptual Framework for Service-Oriented Computing

Given the importance of clients in service-oriented computing, and the ongoing evolution of distributed system realization technologies from client/service architectures, through distributed-object and service-oriented architectures to cloud computing, there is a growing need to lower the complexities and barriers involved in the development of client applications. These range from large scale business applications and business processes to laptop programs and small ”apps” on mobile devices. In this paper we present a unified conceptual framework in which the basic concerns and viewpoints relevant for building clients of service-oriented, distributed systems can be expressed and related to one another in a platform-independent, non-proprietary way. The basic concerns used to structure the framework are the level of abstraction at which a system is represented and the roles from which the software entities of a distributed system are viewed. Using the various concepts and models supported in the framework it is possible to customize and simplify each client developer’s view and to simplify the way in which service providers develop and maintain their services. This paper provides an overview of the framework’s foundations and concepts. We also present the vision behind this conceptual framework and present a small example to show how the models contained in the framework are applied in practice.

Towards High Integrity UDDI Systems

The basic idea of a ubiquitous service market where services can be published by their providers and discovered by potential users is – besides increased interoperability – one of the driving forces behind the SOA vision. However, the failure of the famous UDDI Business Registry demonstrated that service-orientation per se does not solve the problems related to the operation of such service registries – a problem well-known from the component-based development community. On the contrary, since services are highly volatile it is even more difficult to effectively manage a repository. In this paper we discuss the challenges associated with the operation of service brokering solutions with a clear focus on automation and integrity of the overall system as well as the offered search capabilities. To address the identified challenges we propose an extended UDDI architecture.

The role of congregation in service-oriented development

Although they are still being refined, the principles of service-oriented architectures have significant benefits for the maintenance and administration of enterprise systems. However, they are not particularly well suited for supporting the development of client applications and business processes. In particular, the absence of the notion of types, in the sense of abstract data types and object-oriented programming, limits the way in which client application developers can access resources in a service-oriented architecture and leverage reusable assets. In this paper we propose the notion of congregation as a key step and ingredient in service-oriented development that supports flexible deployment and usage of types in an enterprise system. We explain the need for congregation and provide a small motivating example of its application.

Context-Sensitive Service Discovery for Mobile Commerce Applications

Over the last few years the number of services for mobile devices that are connected to the internet via UMTS or wireless 802.11 hotspots has grown tremendously. However, only a small proportion of these applications or services, has been successfully adopted and none has yet turned out to be the hoped-for killer application. We believe that context-sensitive service discovery is the key success factor for mobile applications and could have the same impact and level of success as search engines on desktop computers. Keyword-based searches using typical search engines or portals for browsing services with a mobile device often do not provide satisfying results within a reasonable period of time and they are cumbersome to use because of the restricted and limited input capabilities of mobile devices. In this paper we present a hybrid service discovery approach that uses context information to reduce human device interaction and delivers precise, personalized search results for service requests in a changing environment.