Exogenous Connectors for Software Components

Abstract

Abstract.In existing component models, control originates in components, and connectors are channels for passing on the control to other components. This provides a mechanism for message passing, which allows components to invoke one another's operations by method calls (or remote procedure calls) either directly or indirectly via a channel such as a bus. Thus components in these models mix computation with control, since in performing their computation they also initiate method calls and manage their returns, via connectors. Consequently, in terms of control, components are not loosely coupled. In this paper, we propose exogenous connectors, and demonstrate their use in a small example. In contrast to connectors in existing component models, exogenous connectors initiate calls and manage their returns, and are used to encapsulate control in a component model we are working on. In the example, we demonstrate the feasibility of exogenous connectors, and compare them with connectors in closely related architecture description languages.

Xcd – Modular, Realizable Software Architectures

“…Compared to Exogenous Connectors [24] and Reo [4], XCD differs by introducing role strategies and by not trying to remove interaction constraints from components entirely. We believe that components still need to be able to specify some interaction constraints so as to describe what they expect of their environment and how they plan to use it.…”

(Behavioural) Design Patterns as Composition Operators

“…For architectural units, connectors between ports provide communication channels for indirect message passing. 1 We have defined a component model [18,15] in which composition operators are explicitly defined entities with their own identities. In our model, components are encapsulated : they encapsulate control, data as well as computation, as in 'enclosure in a capsule'.…”

“…In [18] we defined the composition operators informally, and in [15] we defined them in terms of many-sorted first-order logic. In addition, we defined a catalog of composition operators in [32].…”

“…First, it is worth emphasising that, as we saw in Section 3, our composition operators are connectors [18] that encapsulate control. Moreover, these operators themselves can be composed to yield composite operators that also encapsulate control.…”

“…In our work on software component models [18,15], we have defined (a component model with) explicit composition operators. Such operators can themselves be composed into composite operators [13].…”