Achieving this is easier if the agency gives each module a bounded scope and defined structure within a program. As with most IT acquisitions, however, the technical issues in modular contracting are tougher to handle than the legal or administrative ones. Interoperability of the modules is easier said than done. In an ideal world, we'd have accepted, vendor-neutral standards defining interfaces. We don't live in that world.
Standards tend to lag behind technology.
The real world sometimes forces trade-offs between the new technologies and standards. Acquiring a new technology can mean betting that it will become standard. Moreover, proprietary or unique parts of a system can hold the program hostage. Thus, the FAR urges agencies to avoid them. In spite of the risks and challenges, however, modular contracting seems to be the best method for many projects.