Related work The problem of web service composition has been studied extensively in recent years [6, 4]. Hierarchical planning (HTN Planning) [1] is a modern type of planning that tries to resolve problems by dividing them into simpler subproblems. HTN planning has been used successfully in complex domains, like SWS composition [7, 3]. HTN-DL [5] is a new HTN extension in which the domain, the problem and the current state are described using an ontology in OWL. HTN-DL works with the Open World Assumption and takes advantage of the inference capabilities of Description Logics (DL) in the planning process. Furthermore, it can work directly form a description in OWL-S of the available SWS.
Introduction
Semantic Web Services (SWS) are distributed and reusable software components
that are described using standard formal languages like SWDL or OWL-S. SWS
can be automatically discovered, invoked and combined. Complex applications
can be built combining different Web Services and therefore, it is important to
provide assisting tools to help in the composition process [
Planning techniques can be used to find the flow of services that
accomplish a specific task. Several approaches have been tried in software component
composition [
In my thesis I propose to combine CB Planning and HTN-DL to obtain a hierarchical planner that utilizes the best of both worlds.
My proposed approach: Case-Based HTN-DL Planning The main drawbacks of HTN-DL are that it is much slower than classical planning and that needs an exhaustive domain description.
Case-Based Planning [
In my thesis I propose to combine Case Based Planning and HTN-DL in order to obtain the best of both worlds (CB HTN-DL Planning) and apply these ideas to compound SWS. The main features of this new approach are: it works with the Open World Assumption using the DL inference capabilities; it works directly with the OWL-S descriptions of the SWS; it will be able to work without a complete description of the domain; it can use the cases as heuristic to guide the search and enhance the performance; and the planner will presumably improve the performance and accuracy with use because new cases will be learned.
The thesis will have 3 different parts: the formalization of the planning theory behind CB HTN-DL, the development of an example application in a real environment, and the evaluation of the results.