1. A method for deriving and applying sub-iteration contexts in a transformation operation in a data integration system, comprising: receiving a source data instance comprising a plurality of source nodes with associated source node values, and a plurality of source data paths connecting the source nodes; detecting one or more repeating path expressions in the source data instance, wherein a repeating path expression is a source data path that connects two or more source nodes that are siblings to each other; receiving a target template comprising a plurality of explicitly created output nodes (ECONs), wherein the target template specifies a structure of a target data instance; deriving one or more sub-iteration contexts for each ECON in the received target template, wherein each sub-iteration context comprises an association between the ECON and one of the detected repeating path expressions, and wherein each sub-iteration context directs how the ECON will repeat in the target data instance; calculating a set of one or more sub-iteration points and a set of exact bindings from the derived sub-iteration contexts; generating a transformation specification from the set of sub-iteration points and exact bindings; and applying said transformation specification to the source instance data to generate the target data instance.