Ralph Bergmann

Similarity Measures for Object-Oriented Case Representations

Object-oriented case representations require approaches for similarity assessment that allow to compare two differently structured objects, in particular, objects belonging to different object classes. Currently, such similarity measures are developed more or less in an ad-hoc fashion. It is mostly unclear, how the structure of an object-oriented case model, e.g., the class hierarchy, influences similarity assessment. Intuitively, it is obvious that the class hierarchy contains knowledge about the similarity of the objects. However, how this knowledge relates to the knowledge that could be represented in similarity measures is not obvious at all. This paper analyzes several situations in which class hierarchies are used in different ways for case modeling and proposes a systematic way of specifying similarity measures for comparing arbitrary objects from the hierarchy. The proposed similarity measures have a clear semantics and are computationally inexpensive to compute at run-time.

Techniques and Knowledge Used for Adaptation During Case-Based Problem Solving

This paper presents a survey of different adaptation techniques and the used knowledge during adaptation. A process model of CBR and the used knowledge according to the different knowledge containers is introduced. The current models of adaptation are described and illustrated in an example domain.

Representation and Structure-Based Similarity Assessment for Agile Workflows

The dynamics of the market requires workflow management systems that support agile workflows - workflows which are flexible concerning the adaptation to innovations. This paper presents a case-based approach to representation and index-based retrieval of past workflows in order to give authoring support for adaptation of recent workflow instances. The utility of the presented methods is demonstrated by an experimental evaluation.

Representation in case-based reasoning

A case in case-based reasoning is a contextualized piece of experience, which can be represented in various forms. Traditional approaches can be classified into three main categories: feature vector representations, structured representations, and textual representations. More sophisticated approaches make use of hierarchical representations or generalized cases. For particular tasks such as design and planning highly specific representations have been developed.

On the Role of Abstraction in Case-Based Reasoning

This paper addresses the role of abstraction in case-based reasoning. We develop a general framework for reusing cases at several levels of abstraction, which is particularly suited for describing and analyzing existing and designing new approaches of this kind. We argue that in synthetic tasks (e.g. configuration, design, and planning), abstraction can be successfully used to improve the efficiency of similarity assessment, retrieval, and adaptation. Furthermore, a case-based planning system, called Paris, is described and analyzed in detail using this framework. An empirical study done with Paris demonstrates significant advantages concerning retrieval and adaptation efficiency as well as flexibility of adaptation. Finally, we show how other approaches from the literature can be classified according to the developed framework.

Towards case-based adaptation of workflows

Creation and adaptation of workflows is a difficult and costly task that is currently performed by human workflow modeling experts. Our paper describes a new approach for the automatic adaptation of workflows, which makes use of a case base of former workflow adaptations. We propose a general framework for case-based adaptation of workflows and then focus on novel methods to represent and reuse previous adaptation episodes for workflows. An empirical evaluation demonstrates the feasibility of the approach and provides valuable insights for future research.

Case-based reasoning support for online catalog sales

Case-based reasoning uses similarity measures and domain-specific knowledge for information retrieval and problem solving. The paper considers how CBR techniques can be applied to e-commerce applications to enable intelligent sales support. It reviews the limitations of ordinary databases to this task and then examines CBR techniques that can improve the usefulness of electronic catalogs. It describes an implementation of a CBR-based system in a specific application domain, and concludes with brief descriptions of two projects at the University of Kaiserslautern that advance these systems.

Structural Adaptation of Workflows Supported by a Suspension Mechanism stand by Case-Based Reasoning

Collaborative, long-term processes with changing requirements occur in several domains. In design and manufacturing, we observed the following particular characteristics: the process models can be huge and contain longsome decisions while the time to market is tight. Furthermore, different types of products have to be considered. In this paper, we present an approach of new, flexible workflow technology that provides a solution for this: The ongoing workflows can be adapted by means of late-planning and ad-hoc changes. A suspension mechanism allows the workflow designers to modify parts of a workflow while the remainder of the workflow can continue to be executed. A case-based reasoning approach supports the reuse of past experience for this.

Case-based adaptation of workflows

This paper presents on a Case-based Reasoning approach for automated workflow adaptation by reuse of experience. Agile workflow technology allows structural adaptations of workflow instances at build time or at run time. The approach supports the expert in performing such adaptations by an automated method. The method employs workflow adaptation cases that record adaptation episodes from the past. The recorded changes can be automatically transferred to a new workflow that is in a similar situation of change. First, the notion of workflow adaptation cases is introduced. The sample workflow modeling language CFCN is presented, which has been developed by the University of Trier as a part of the agile workflow management system Cake. Then, the retrieval of adaptation cases is briefly discussed. The case-based adaptation method is explained including the so-called anchor mapping algorithm which identifies the parts of the target workflow where to apply the changes. A formative evaluation in two application domains compares different variants of the anchor mapping algorithm by means of experts assessing the results of the automated adaptation.

An investigation of generalized cases

In the CBR literature from the past 25 years there is a considerable amount of research work that makes use of cases that are subspaces of some representation space rather than points in it. For cases of that kind, different terms have been used such as generalized case, prototype, schema, script, or abstract case. Our analysis of selected publications yields that on the one hand the same term is used for different concepts and on the other hand different terms are used for more or less the same concepts. So our goal is to improve the conceptual clarity by proposing an integrated classification schema for cases. We then use this schema to describe semantically founded ways for similarity definition and computation, depending on the class membership of query and case.