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Querying and retrieval

Users begin a session with AIR by describing their information need, using a very simple query language. An initial query is composed of one or more clauses. Each clause can refer to one of the three types of ``features'' represented in AIR's network: keywords, documents or authors, and all but the first clause can be negated. This query causes activity to be placed on nodes in AIR's network corresponding to the features named in the query. This activity is allowed to propagate throughout the network and the system's response is the set of nodes that become most active during this propagation.

The traditional result of a query is only documents. AIR also provides keywords and authors. Keywords retrieved in this manner are considered RELATED TERMS that users may use to pursue their searches. Retrieved authors are considered to be closely linked to the subject of interest. There are many ways in which a user might find related terms and centrally involved authors a valuable information product in their own right.

Figure (figure) shows AIR's response to a typical query: \small {\tt ((:TERM ``ASSOCIATIVE'')(:AUTH ``ANDERSON,J.A.''))} This is the network of keywords, documents and author's considered relevant to this query. The nodes are drawn as a tri-partite graph, with keywords on the top level, documents in the middle and authors on the bottom. Associative links that helped to cause a node to become retrieved (and only those links) are also displayed. Heavier lines imply stronger associative weights. AIR uses directed links, and this directionality is represented by the concavity of the arcs; a clockwise convention is used. For example, a link from a document node (in the middle level) to a keyword node (in the top level) goes clockwise, around to the left.

Actually, this is only a picture of the final state of the system's retrieval. The network is actually drawn {incrementally}, with the first nodes to become significantly active being drawn first and in the middle of the pane. As additional nodes become active at significant levels, they are drawn farther out along the three horizontal axes and the links through which they became active are drawn as well. This dynamic display has at least two real advantages. First, the fact that AIR provides the first part of its retrieval almost immediately means that the user is not impatiently waiting for the retrieval to complete (typically 5-10 seconds in this implementation). Second, displaying the query's dynamics helps to give the user a tangible feeling of ``direct manipulation'' [REF654] ; the user ``prods'' the network in a certain place, and then watches as waves of activity flow outward from that place.


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