18. The computer system of claim 1 , wherein the second query language statement requests the requested data set to be provided and the relation store includes other algebraic relations for data sets that are not composed from the second query language statement, the computer program instructions further comprising instructions for using at least some of the other algebraic relations to provide the requested data set.
1. A computer system comprising: (a) at least one processor; (b) at least one memory, wherein the at least one memory includes a relation store and a data set information store; and (c) computer program instructions stored in the memory and configured to be executed by the processor to provide a requested data set, including: (i) instructions for receiving a first query language statement referencing a plurality of data sets; (ii) instructions for storing information in the data set information store regarding the data sets referenced in the first query language statement, including temporal information regarding the data sets referenced in the first query language statement; (iii) instructions for composing a first plurality of algebraic relations referencing the data sets specified in the first query language statement, wherein each of the algebraic relations in the first plurality of algebraic relations comprises a respective first expression including a symbolic representation of at least a first respective data set, a respective second expression including a symbolic representation of at least a second respective data set, and a relational operator symbolically defining a mathematical relationship between the respective first expression and the respective second expression; (iv) instructions for storing the first plurality of algebraic relations in the relation store; (v) instructions for receiving a second query language statement referencing a second plurality of data sets; (vi) instructions for composing a second plurality of algebraic relations referencing the data sets specified in the second query language statement; (vii) instructions for storing the second plurality of algebraic relations in the relation store; (viii) instructions for providing the requested data set in response to the second query language statement using at least one algebraic relation from the first plurality of algebraic relations and at least one algebraic relation from the second plurality of algebraic relations; and (ix) instructions for removing at least some of the first plurality of algebraic relations from the relation store based, at least in part, on the temporal information regarding the data sets referenced in the first query language statement.