1. A method of accessing data in a data source using a computer system: receiving a selection of a series of steps to be performed in accessing the data, each step in the series of steps including a type, a definition of the inputs and outputs, a definition of data accessing characteristics for the step, and an indication of whether original data or copies of the data are used in the step; receiving a selection of interconnections among the series of steps to create a plan, the plan defining the execution order of the series of steps; and executing the plan to access the data.