| 摘要 |
A data exploration tool which has a graphical user interface that employs di rected graphs to provide histories of the data exploration operations. Nodes in the directed graphs represent operations on data; the edges represent relationships betwe en the operations. One type of the directed graphs is the derivation graph, in whic h the root of the graph is a node representing a data set and an edge leading from a fi rst node to a second node indicates that the operation represented by the second node is performed on the result of the operation represented by the first node. Oper ations include query, segmentation, aggregation, and data view operations. A user m ay edit the derivation graph and may select a node for execution. When that is done, all of the operations represented by the nodes between the root node and the select ed node are performed as indicated in the graph. The operations are performed using techniques of lazy evaluation and encachement of results with the nodes. Ano thertype of the directed graphs is the subsumption graph , in which an edge leading from a first node to a second node indicates that the second node stands in a sub sumption relationship to the first node. If a result of the operation represented by the first node has been computed, the result is available to calculate the result of the op eration represented by the second node.
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