A method comprising: receiving new program code that specifies a modification to a first configuration of a running application, the first configuration of the running application including a first set of program modules (108, 110) provided in memory, the first set of program modules being described by a first version of an application manifest; in response to said receiving: updating the first version of the application manifest to create a second version of the application manifest; and updating the first configuration of the running application to provide a second configuration of the running application, while the first configuration of the running application continues to run, the second configuration of the running application including a second set of program modules that is described by the second version of the application manifest, a subset of one or more program modules in the second set of program modules also belonging to the first set of program modules; and consulting a mapping component when a calling program module in the second configuration of the running application invokes a function, the mapping component including mapping logic specified by the second version of the application manifest, the first version of the application manifest including a first version of the mapping logic, and said updating of the first version of the application manifest including updating a part of the first version of the mapping logic that is impacted by the new program code, and not updating another part of the first version of the mapping logic. receiving new program code that specifies a modification to a first configuration of a running application, the first configuration of the running application including a first set of program modules (108, 110) provided in memory, the first set of program modules being described by a first version of an application manifest; in response to said receiving: updating the first version of the application manifest to create a second version of the application manifest; and updating the first configuration of the running application to provide a second configuration of the running application, while the first configuration of the running application continues to run, the second configuration of the running application including a second set of program modules that is described by the second version of the application manifest, a subset of one or more program modules in the second set of program modules also belonging to the first set of program modules; and consulting a mapping component when a calling program module in the second configuration of the running application invokes a function, the mapping component including mapping logic specified by the second version of the application manifest, the first version of the application manifest including a first version of the mapping logic, and said updating of the first version of the application manifest including updating a part of the first version of the mapping logic that is impacted by the new program code, and not updating another part of the first version of the mapping logic. updating the first version of the application manifest to create a second version of the application manifest; and updating the first configuration of the running application to provide a second configuration of the running application, while the first configuration of the running application continues to run, the second configuration of the running application including a second set of program modules that is described by the second version of the application manifest, a subset of one or more program modules in the second set of program modules also belonging to the first set of program modules; and consulting a mapping component when a calling program module in the second configuration of the running application invokes a function, the mapping component including mapping logic specified by the second version of the application manifest, the first version of the application manifest including a first version of the mapping logic, and said updating of the first version of the application manifest including updating a part of the first version of the mapping logic that is impacted by the new program code, and not updating another part of the first version of the mapping logic.