30. A machine-readable storage medium embodying instructions which, when executed by a machine, cause the machine to perform operations comprising: accessing a relationship definition file having at least one relationship definition associated with a package of data items, the at least one relationship definition identifying a class of relationships between data items included in the package of data items, the at least one relationship definition associating a main file with information stored in a related file, the at least one relationship definition including a template string and a first pattern string; accessing a main file name of the main file; matching the main file name to the first pattern string; and deriving a second pattern string from the template string, wherein the information stored in the related file is related to information contained in the main file, and wherein the information stored in the related file is for use in rendering the main file, by an electronic document rendering application, without altering the information contained in the main file.
30. A machine-readable storage medium embodying instructions which, when executed by a machine, cause the machine to perform operations comprising: accessing a relationship definition file having at least one relationship definition associated with a package of data items, the at least one relationship definition identifying a class of relationships between data items included in the package of data items, the at least one relationship definition associating a main file with information stored in a related file, the at least one relationship definition including a template string and a first pattern string; accessing a main file name of the main file; matching the main file name to the first pattern string; and deriving a second pattern string from the template string, wherein the information stored in the related file is related to information contained in the main file, and wherein the information stored in the related file is for use in rendering the main file, by an electronic document rendering application, without altering the information contained in the main file. 32. The machine-readable storage medium of claim 30 , wherein the template string includes a name portion symbol, the name portion symbol identifying a portion of the main file name, and wherein the machine-readable medium embodies further instructions which, when executed by a machine, cause the machine to perform the method wherein the deriving of the second pattern string comprises: generating the second pattern string corresponding to the template string, the name portion symbol in the template string being replaced in the second pattern string by the portion of the main file name identified by the name portion symbol.