Described is a data integration technique and system for providing data in response to a request. The data integration system may overcome the limits of a fixed scheduling system by implementing a service dependency graph (SDG). In particular, the data integration system may represent the SDG as a directed acyclic graph (DAG). Accordingly, the system may leverage the nature of DAGs in order to derive an efficient topological ordering for calling one or more services. Thus, the data integration system may retrieve and compile data in an efficient and scalable manner.