16. A data analysis system for performing a data analysis task having an associated analysis context, the system comprising: a processor configured to define the analysis context associated with the data analysis task, wherein data items have a variable relevance in accordance with the context, and wherein data items are grouped together to form logical transactions conducted by a user over a predetermined time period; a network interface configured to receive the logical transactions exchanged over a communication network; the processor configured to define a plurality of logical transactions based on one or more transaction criteria, wherein each logical transaction of the plurality of logical transactions comprise at least two data items of the plurality of data items, process the logical transactions with a set of prioritization rules to generate relevance scores that quantify a relevance of the logical transactions to the analysis context, wherein the relevance scores are assigned according to a common scale, and generate a prioritization of the logical transactions based on the relevance scores.
16. A data analysis system for performing a data analysis task having an associated analysis context, the system comprising: a processor configured to define the analysis context associated with the data analysis task, wherein data items have a variable relevance in accordance with the context, and wherein data items are grouped together to form logical transactions conducted by a user over a predetermined time period; a network interface configured to receive the logical transactions exchanged over a communication network; the processor configured to define a plurality of logical transactions based on one or more transaction criteria, wherein each logical transaction of the plurality of logical transactions comprise at least two data items of the plurality of data items, process the logical transactions with a set of prioritization rules to generate relevance scores that quantify a relevance of the logical transactions to the analysis context, wherein the relevance scores are assigned according to a common scale, and generate a prioritization of the logical transactions based on the relevance scores. 19. The system of claim 16 wherein the plurality of data items comprises a web page, an e-mail message, a file transfer session, an instant messaging chat session, and a textual transcript of a telephone call.