6. 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, wherein the logical transactions include a first data item type and a second data item type that is different from the first data item type; the processor configured to 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.
6. 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, wherein the logical transactions include a first data item type and a second data item type that is different from the first data item type; the processor configured to 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. 9. The system of claim 6 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.