Towards a Theory of Glue

Abstract

We propose and study the notions of behaviour type and composition operator making a first step towards the definition of a formal framework for studying behaviour composition in a setting sufficiently general to provide insight into how the component-based systems should be modelled and compared. We illustrate the proposed notions on classical examples (Traces, Labelled Transition Systems and Coalgebras). Finally, the definition of memoryless glue operators, takes us one step closer to a formal understanding of the separation of concerns principle stipulating that computational aspects of a system should be localised within its atomic components, whereas coordination layer responsible for managing concurrency should be realised by memoryless glue operators.

A Theory Agenda for Component-Based Design

“…A general formalisation of the notions of component framework and glue is provided in [13]. Below, for the sake of simplicity, we assume that components are characterised by their behaviours specified directly as Labeled Transition Systems (LTS).…”

“…Systems are constructed from two types of components, respectively masters (M ) and slaves (S). Every master m i requests sequentially two distinct slaves s j , s k (rules 13,14) and then interacts with both of them (rule 15 above). The rules are graphically depicted in Figure 5.…”

“…We define two additional architectures A 13 and A 23 similar to A 12 : they consist, respectively, of coordinating components D 13 One can define a canonical lattice on the set of architectures. The lattice is induced by the partial order relation <, defined by putting A 1 < A 2 if and only if A 1 ⊕ A 2 ∼ = A 1 .…”