Facilitating representation and retrieval of structured cases: Principles and toolkit

Case-Based reasoning (CBR) applications are increasingly used for problems involving structured data, especially in process-oriented domains. Available CBR frameworks rely primarily on flat case representations, leaving developers of process-oriented CBR systems without general-purpose tools aimed at their needs. This paper discusses needs to support structure-based retrieval for CBR and how they have been addressed in the development of the Structure Access Interface (SAI), a toolkit for representation and retrieval of structured cases which is now available for general use. Integrating SAI into a CBR project eliminates the need for developing a storage scheme for graph data structures and facilitates the development of retrieval algorithms by (1) providing useful code for common retrieval tasks and (2) delineating the tasks which may require domain-specific implementations. SAI maintains flexibility through its customizability yet carries solutions for many common tasks for CBR developers, as well as illuminating some general principles for addressing common representation and retrieval needs for process-oriented CBR tasks and the relationship between CBR needs for structured retrieval and needs and methods in graph oriented database research. The paper closes with an evaluation of SAI's scalability and demonstration of the value of enabling developers to select retrieval methods suited to their tasks. It closes with a discussion of SAI's relationship to the growing body of work on graph databases.