7. The computer system of claim 5 , wherein said method further comprises: registering a plurality of mapping domains, each registered mapping domain indicating a mapping between a corresponding type of source schema model and a corresponding type of target schema model; selecting a mapping domain of said plurality of mapping domains based on a selection of said mapping domain by a user of said computer system, wherein said selected mapping domain indicates a type of said mapping model; and editing said mapping model by opening a graphical user interface based on said selected mapping domain and by providing semantic extensions based on said selected mapping domain, wherein said provided semantic extensions specify functionality required by said selected mapping domain.
5. A computer system, said system comprising: a central processing unit (CPU); a memory coupled to said CPU; a computer-readable, tangible storage device coupled to said CPU, said storage device containing program instructions that are executed by said CPU via said memory to cause the computer system to specify, in a schema mapping framework, a method for specifying a mapping between a source schema model and a target schema model, said method comprising: storing, in said memory coupled to said CPU, a first plurality of mapping objects separate from said source and target schema models so that an annotated embedding of said first plurality of mapping objects within said source or target schema model is not required, said first plurality of mapping objects resulting from a serialization of said source schema model, said serialization of said source schema model included in a serialization of a mapping model of said schema mapping framework, and said mapping model representing said mapping between said source schema model and said target schema model; resolving, by a processor coupled to said CPU, a first set of one or more path expressions to one or more source objects, said one or more source objects represented by said first set of one or more path expressions included in said first plurality of mapping objects, wherein said resolving said first set of one or more path expressions includes: identifying a path expression of said first set of one or more path expressions, wherein said path expression of said first set of one or more path expressions includes an identification of a first computer file that includes said serialization of said source schema model; opening said first computer file using said identification of said first computer file; storing, in said memory coupled to said CPU and responsive to said opening said first computer file, said serialization of said source schema model as a first tree data structure representing a first plurality of hierarchical levels of said first plurality of mapping objects; and traversing one or more source logical objects of a mapping model tree in said memory to locate said one or more source objects that are associated with said one or more source logical objects in a one-to-one correspondence via said first set of one or more path expressions, said mapping model tree representing said mapping model, and said one or more source logical objects including said first set of one or more path expressions, wherein said traversing said one or more source logical objects includes storing in each source logical object a pointer to a corresponding source object of said one or more source objects; storing, in said memory, a second plurality of mapping objects separate from said source and target schema models so that an annotated embedding of said second plurality of mapping objects within said source or target schema model is not required, said second plurality of mapping objects resulting from a serialization of said target schema model, and said serialization of said target schema model included in said serialization of said mapping model of said schema mapping framework; and resolving, by said processor coupled to said CPU, a second set of one or more path expressions to one or more target objects, said one or more target objects represented by said second set of one or more path expressions included in said second plurality of mapping objects, wherein said resolving said second set of one or more path expressions includes: storing in said mapping model tree a target side set of one or more pointers to said one or more target objects; identifying a path expression of said second set of one or more path expressions, wherein said path expression of said second set of one or more path expressions includes an identification of a second computer file that includes said serialization of said target schema model; opening said second computer file using said identification of said second computer file; storing, in said memory and responsive to said opening said second computer file, said serialization of said target schema model as a second tree data structure representing a second plurality of hierarchical levels of said second plurality of mapping objects; and traversing one or more target logical objects of said mapping model tree in said memory to locate said one or more target objects that are associated with said one or more target logical objects in a one-to-one correspondence via said second set of one or more path expressions, said one or more target logical objects including said second set of one or more path expressions, wherein said traversing said one or more target logical objects includes storing in each target logical object a pointer to a corresponding target object of said one or more target objects.