A fundamental activity in the University of Michigan Digital Library (UMDL) is connecting people/agents that need help accomplishing their tasks with people/agents that are capable of doing those tasks. A canonical example is that of a library user in search of information who needs to contact the appropriate collections which contain the information. The job of a task planning agent (TPA) is to forge these connections between agents -- to help agents team up with the right agents in a large, open, and constantly evolving network of agents.
We envision that there will be many TPAs within the UMDL. They will have in common the general role of finding resources (agents with capabilities and/or content of interest), but each will possess specific knowledge and procedures for doing so, depending both on the characteristics of the tasks that are in need of resources, and on the resources available for doing the search (e.g. monetary funds, user patience, etc.). The class of tasks that we are initially focusing on are, not surprisingly, query answering tasks. Thus, in this paper, we will consider the subclass of TPAs that are specialized for query tasks, and will focus specifically on how we have designed and built an instance of a TPA for query planning.
Figure 1: Schematic view of the UMDL architecture showing the agents in
it and the communications between them. The solid lines represent the
first part of the search, where the UIA looks for applicable
collections. The dashed lines are the second part, when the UIA
queries the collections that were found. Future versions will have
several instantiations of each agent.
A query planning TPA is ultimately responsible for finding one or more collections based on the needs of a user; in order to do so, it communicates with many agents in the UMDL, as seen in Figure 1. The TPA receives the specification of the user's needs, along with parameters concerning task planning such as constraints on the number of collections to find or the effort to expend in finding them, from the User Interface Agent (UIA) which interacts directly with the user. The TPA needs to examine the query task to identify the characteristics of collections that might satisfy it, and from this formulate a query to the Registry Agent (RA) to see whether such collections exist. The TPA can inspect the responses from the RA and might simply forward (a subset of) them back to the UIA -- but, more often, what is returned does not satisfy the constraints of the query task. The TPA possesses procedural knowledge about how to handle such cases, which could in turn involve enlisting the help of other agents in the network, such as agents that can broaden/narrow topics of search (Broad System of Ordering Agents (BSOAs)) and agents that can provide synonymous terms (Thesaurus Agents (TAs)). Moreover, for a candidate collection, the TPA could contact the Collection Interface Agent (CIA) associated with it, to probe more deeply into its capabilities, content, price, or availability. Ultimately, the TPA formulates a candidate set of collections for the user to contact, and returns the set to the UIA. The UIA might then proceed to contact some of these CIAs directly and ask for the particular documents, before returning the final answer to the user.