Dietmar Stoll

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.

Strategies for the Run-Time Testing of Third Party Web Services

Because of the dynamic way in which service-oriented architectures are configured, the correct interaction of service users and service providers can only be fully tested at run-time. However, the run-time testing of web services is complicated by the fact that they may be arbitrarily shared and may have lifetimes which are independent of the applications that use them. In this paper we investigate this situation by first identifying the different types of tests that can be applied to services at run-time and the different types of web services that can be used in service-oriented systems. We then discuss how these can be combined - identifying the combinations of tests and web services that make sense and those that do not. The resulting analysis identifies six distinct forms of run-time testing strategy of practical value in service-oriented systems.

Orthographic modeling environment

The rise in importance of component-based and service-oriented software engineering approaches over the last few years, and the general uptake in model-driven development practices, has created a natural interest in using languages such as the UML to describe component-based systems. However, there is no standard way (de jure or de facto) of using the various viewpoints and diagram types identified in general model-driven development approaches to describe components or assemblies of components. To address this problem, we have developed a prototype IDE which provides a systematic and userfriendly conceptual model for defining and navigating around different views of components and/or component-based systems. This is supported by an infrastructure that allows the IDE to be extended with tools that create views and check consistency in an easy and systematic way, and a unifying metamodel which allows all views to be generated automatically from a single underlying representation of a component or component-based system.

Orthographic Service Modeling

As the size and complexity of services has grown over the years, so has the number of different models and view types used to visualize them. However, in most development environments used today, views are usually organized in a fairly simple way within an arrangement of trees, and are often mixed arbitrarily with the artifacts they contain or visualize. In this position paper we propose a new paradigm for creating, organizing and managing the different views that are required in modern software development projects inspired by the orthographic projection paradigm that has been used for many years in other engineering disciplines. The approach therefore makes software engineering environments more like computer-aided design (CAD) tools for physical products. After explaining the basic idea behind the approach, which we refer to as Orthographic Service Modeling (OSM), we outline its three key ingredients - (1) on- demand view generation, (2) dimension-based navigation (3) and an inherently view-based method.

Separating per-client and pan-client views in service specification

Service-oriented architecture is predicated on the availability of accurate and universally-understandable specifications of services which capture all the information that a potential user needs to know to use the service. However, WSDL, the most widely used service specification standard, only allows the syntactic signatures of the operations offered by a service to be described. This not only makes it difficult to specify context sensitive information, such as acceptable operation invocation sequences and drive service discovery through client-oriented requirements, it is also an inappropriate level of abstraction for a human friendly description of a services capabilities. The current thinking is that context sensitive information such as operation sequencing rules should be described in an accompanying specification document written in an auxiliary language. For example, WS-CDL is a well known auxiliary language for writing choreography descriptions that capture interaction scenarios in terms of abstract roles and participants. However, this approach not only decouples the additional information from the core WSDL specification, it also describes it in terms of abstractions which may not match those used (implicitly or explicitly) by the service. In this paper we investigate this issue in greater depth, explore the different solution patterns and propose a new specification approach which rectifies the identified problems.

A prototype implementation of an orthographic software modeling environment

Orthographic Software Modeling (OSM) is a view-centric software engineering approach that aims to leverage the orthographic projection metaphor used in the visualization of physical objects to visualize software systems. Although the general concept of OSM does not prescribe specific sets of views, a concrete OSM environment has to be specific about the particular views to be used in a particular project. At the University of Mannheim we are developing a prototype OSM environment, nAOMi, that supports the views defined by the KobrA 2.0 method, a version of KobrA adapted for OSM. In this paper we provide an overview of the KobrA 2.0 metamodel underpinning nAOMi and give a small example of its use to model a software system.