1. A method for updating a computer-readable data storage medium with the aid of a particular microprocessor tied to said computer-readable data storage medium, said data storage medium containing interaction data, said interaction data being representative of interactions within a cell, said method comprising: providing said microprocessor with a global measurement of activity in a cell, causing said microprocessor to retrieve, from a database stored on a computer-readable medium, said interaction data, said interaction data including data representative of a subset of interactions within the cell, each of said interactions being consistent with said global measurement, causing said microprocessor to determine an aggregate cost for each of said interactions, causing said microprocessor to determine which of said interactions from said subset of interactions has a minimum aggregate cost, causing said microprocessor to provide output representative of said minimum cost interaction, and causing said output to be stored in said computer-readable data storage medium, and representing said data from said database as an interactome, said interactome having nodes representing molecules, and edges connecting pairs of said nodes, each edge representing an interaction between molecules represented by said nodes, wherein causing said microprocessor to determine which of said signaling pathways from said subset of signaling pathways has a minimum aggregate cost comprises solving a prize-collecting Steiner tree problem associated with said interactome to identify said pathways.