Figure 5 shows the query interface for a simple query. The KEYWORDS field is where the user enters the keywords-based query condition. The user also has the following options available: (1) a choice of ``AND'' or ``OR'' boolean stringing of keywords, (2) a specification of the number of resulting objects to be shown on each page, (3) a selection of partial matching or exact matching of keywords, and (4) a choice of how much information is desired to be presented in the result. The access path for a simple query is generated by utilizing information brokers which support keyword based searching. For example, in processing a simple query on the keywords, job and multimedia, our system answers the query by selecting all information brokers which provide general keyword based search services and have registered in Diorama such as Yahoo and Harvest.
In addition to directly submit a simple query, we also provide the Simple Query Tracing option [16]. The simple query processing is currently composed of a five step process: (1) source selection, (2) for each source, translation of the simple query form data into a valid URL address to that source, (3) parallel execution of each subquery against an individual source, (4) translation of each subquery result into the consumer's preferred result representation, and (5) the merging of the subquery results from different sources into the final result format. The first step of source selection is done by selectively clicking the Choose Repositories selection box in Figure 5. To monitor the other four steps of simple query processing, the query is decomposed and presented in an interactive interface to allow the user to trace each of the above processing steps. Figure 6 shows a result of this simple query, which is produced by combining the search results from all the available data sources selected to answer the query.