1. A system comprising: a memory; and a processor coupled to the memory, the processor configured to: determine that a query includes a first function for whose evaluation an index is not natively provided by an event processing system that is to compile the query; provide a data cartridge to the event processing system, the data cartridge providing an indexing scheme for evaluating the first function of the query; and use, by the event processing system, the indexing scheme provided by the data cartridge to evaluate the first function of the query, wherein the processor is further configured to: determine an occurrence of a link definition in the query, the link definition identifying the first function and the data cartridge; determine a list of input arguments to the first function, wherein the list of input arguments comprises a collection; determine whether the data cartridge provides an index for evaluation of the first function with the set of input arguments; compile the query using information provided by the data cartridge to generate executable code, the executable code comprising an index instance generated using the information provided by the data cartridge, the index instance being generated for evaluation of the first function; and execute the executable code, wherein the execution causes execution of the first function provided by the data cartridge related to the index instance.