1. A method for mapping persistence requests to Structured Query Language (SQL) statements using a two-layer architecture for processing structured persistence requests and object-based container persistence, the method comprising: receiving a persistence request at an interpreting layer; employing a set of one or more interpreting layer classes selected from the group comprising: a “ConditionProcessor class,” a “SimpleConditionProcessor class,” an “ArithmeticExpressionProccssor class,” and a “StringExpressionProcessor class;” generating a command sequence for the persistence request, wherein the command sequence is generated by traversing a first tree structure when the persistence request is a structured persistence request and wherein the command sequence is generated without traversing a tree structure by translating one or more object-based “Load, ” Store, ” and/or “Remove” method calls when the persistence request is an object-based container persistence request; passing the command sequence in step-wise fashion to an SQL assembly layer during traversal of the first tree structure; and employing a set of one or more assembly layer classes to assemble a database-independent SQL statement in step-wise fashion based, at least in part, on the command sequence, wherein the assembled database-independent SQL statement is portable across databases from different vendors and wherein each element of the assembled database-independent SQL statement is represented by a node of a second tree structure.