1. A computer program product comprising one or more physical computer storage device having thereon computer-executable instructions that are structured such that, when executed by one or more processors of a computing system, cause the computing system to perform a method for performing an extract and transform of data from a plurality of data sources, the method comprising: an act of the computing system repeatedly performing an extraction operation on a plurality of data sources; an act of the computing system periodically performing a transformation operation on the extracted data, wherein the act of periodically performing a transformation operation for each of at least one iteration of the transformation operation comprises: for at least some of the extracted data that are valid, an act of performing a transformation operation on the valid data; for at least some of the extracted data that are dependent on other data that is not yet extracted, and an act of identifying the extracted data element as suspect; and for at least some extracted data that had been marked as suspect in a prior interaction of the transformation operation, an act of completing transformation of the previously-marked suspect data.