Composition rules allow building up KL-structures by establishing different types of connections among KL-components. The formal descriptions of KL-structures abstract -through a naming scheme- from their constituents (KL-components or other KL-structures) and emphasize the relationships (task decomposition, data and/or control flow) that establish among them. The introduction of modular formal descriptions for KL-structures allows us to provide views of a formal KL-model at different levels of abstraction.
Each composition rule is described indicating: (1) the types of KL-components and/or KL-structures (constituents) that can be connected through it; (2) the compatibility conditions that must satisfy the formal descriptions these KL-components and/or KL-structures in order for the rule to be applicable; and (3) the formal description of the extended KL-structure built up from them.