Architectural specifications in CASL are formed by declaring the units that are to be implemented separately, also indicating how they are to be linked together to give the desired result. Section 5.1 considers various pragmatic issues affecting the CASL design. Section 5.2 presents the main concepts that underly the semantics of architectural specifications. Finally, Section 5.3 provides examples that illustrate the CASL language constructs for use in architectural specifications.