Web services used to realize a business process may be provided by several, external parties. This implies that management of Web services goes beyond traditional system management, in that it must be able to deal with changes Category Related Work Section Relevant Chapter(s)
Conceptual Service Management 6.2 2
Model Management 6.3 2 & 3 Interoperability Service Interoperability 6.4 3,4 & 5
Service Composition 6.5 4 & 5
Adaptation Workflow Evolution 6.6 5
Service Adaptation 6.7 2 & 5 Table 6.1: Categorization of related work
originating outside their domain (hence, in external Web services). To ensure that these Web services perform adequately, Web service management is needed. A survey on Web service management is provided by Papazoglou &
van den Heuvel (2005).
To guarantee interoperability between management solutions, a dedi-cated task force in OASIS defined the Web Services Distributed Management (WSDM) specification. WSDM consists of two orthogonal parts, namely management of Web services (MOWS) (OASIS, 2004) and management us-ing Web services (MUWS) (Bullard & Vambenepe, 2006). MUWS addresses management of IT resources by defining a set of manageability interfaces, while MOWS may be perceived as an application of MUWS focusing on the management of the Web services themselves. For a similar purpose the WS-Management standard was created, however it lacks an explicit concept of relationships needed for inter-organizational changes. In our work, we use concepts and ideas from both WSDM and WS-Management in order to realize the ASOA.
An approach that studies the relation between Autonomic Computing (AC) and WSDM is presented in (Martin et al., 2007). In this paper the au-thors re-implement a prototype system called Autonomic Web Services En-vironment (AWSE)(Tian et al., 2005) following the WSDM standard. This comparison provides useful insights in the practical and architectural prob-lems that occur when implementing WSDM. However, in AWSE the authors make a distinction between a performance interface and a goal interface.
The performance interface exposes methods for the meta-data and the goal provides methods to query. However, what a goal constitutes is not defined.
In our work, we define the goal to be a property of a model, which may be performance.
Another framework concerning Web services drawing inspiration from Autonomic Computing is PAWS (Ardagna et al., 2007). This framework for flexible an adaptive execution of managed Web service-based business processes covers both design-time and run-time aspects of adaptive services.
The presented case study is based only on Quality-of-Service and no other aspects of software are described.
Casati et al. (2003) view Web service management from a business per-spective. In this paper, the authors advocate a holistic approach which in-cludes business protocols as well as metrics such as Quality-of-Service. How-ever, the approach described remains conceptual and no implementation or
validation results are shown.
In (Cox & Kreger, 2005) the authors describe requirements of managing services within the context of the whole life cycle of a service. The authors make a distinction between development, testing and production require-ments and in addition distinguish layers such as the business process layer, the service layer and the IT infrastructure. As stated this work provides only requirements.
A conceptual management framework that is aimed at service evolution is the Service Evolution Management Framework (SEMF) by Treiber et al.
(2008b,a). The framework is build on top of a conceptual model distinguish-ing between factors of influence (causes of changes), for instance the devel-oper or the hosting environment and information sources such as Quality-of-Service or documents. In the context of our definition of adaptation, the framework aims to develop a framework for detecting/monitoring the evolu-tion of changes and does not tackle automatically adapting to changes.
Another approach aimed at tackling the conceptual scope of service evo-lution management is (Andrikopoulos et al., 2008). The authors specify char-acteristics of service evolution management such as identification of changes, propagation analysis, validation and compliance, version control and instance migration. Furthermore, a Service Specification Reference Model and opera-tors for capturing changes are introduced. However, the work remains on an abstract level and it does not describe how adaptation of a service is enacted.
In (Ludwig et al., 2009; Wassermann et al., 2009), the authors discuss the issues and challenges in cross-domain change management. Change manage-ment deals with the process of implemanage-mentation a change in a complex IT environment where it is assumed that many dependencies between compo-nents are unknown and that the process is done (largely) by hand. The approach proposed complements our approach in that they tackle the ques-tion of how changes are notified and how different parties can work together in order to create a new version of the inter-organizational business process.
From an adaptation perspective, the authors provide a framework for mon-itoring and change detection. However, the decision of how to adapt and whether the software is adaptable is not discussed.
Another work on dealing with the management of service evolution is by von Susani & Dugerdil (2009). The authors suggest that due to the dependencies between services, the migration of a service to a new version should be scheduled. The work provides insights in how changes will be
communicated concerning a termination time for the old version and with possible overlap with the new version. Although the suggestions in the work have merit, no results of following this approach are shown.
An approach that describes an implementation is (Cibrán et al., 2007).
In this work the authors introduce the Web Service Management Layer (WSML). This is a layer placed between client and external Web services.
It supports some management functions, such as service selection, billing, accounting and transactions. The authors rely on an Aspect-Oriented Pro-gramming language to interweave management aspect with the client appli-cation. Concerning adaptation the approach deals only with service selec-tion. Drawbacks of using Aspect-Oriented Programming for realizing adap-tive behavior are discussed in Section 6.7.
Another approach containing a prototypical implementation is (Liu, 2009).
Similar to our approach the author expresses that management should use models and that managing is a process. The author proposes three strate-gies of dealing with changes, namely: heuristic, policies and machine learn-ing. Unlike our implementation aimed at interoperability, the authors target Quality-of-Service.
Our contribution: Management approaches, with the notable exception of (Cibrán et al., 2007) and (Liu, 2009), present only conceptual frameworks (or requirements) and deliver no proof by means of an implementation. Man-agement deals with all aspects of a service and is therefore cumbersome to implement. This in contrast to adaptation which is typically regarded in the context of a single criterium. In this thesis, we provide both a conceptual framework for dealing with any type of change, and describe a proof-of-concept prototype focussed on an important functional aspect of services, namely interoperability.