Deployment Contracts for Software Components

Kung-Kiu Lau and Vladyslav Ukis
School of Computer Science, The University of Manchester
Manchester M13 9PL, United Kingdom
kung-kiu,vukis@cs.man.ac.uk

Abstract:
Today's approaches to software architecture mostly regard components
to be black boxes with interfaces. A component's interface is made up
of signatures of operations offered by the component. The interface is
the only entity visible outside of component. This means that component 
composition can be done only at the interface level since component's 
interiors are hidden in the black box. Although composition at the
interface level empowers com ponent integrators to compose applications 
out of preexisting components, the information visible outside component 
is not su±cient to reason about component composition. In other words, 
compositional reasoning is hardly supported by current approaches to 
software architecture. Furthermore, predictable assembly of components 
is currently not supported. In this report, we present an approach to 
augment component's interface with meta-data. The metadata describes 
component's behaviour. In particular, our metadata set is comprised of 
attributes describing component's environmental dependencies as well as
threading model. The metadata is analysed to allow compositional reasoning 
of components. Moreover, we consider two widely-spread execution environments 
of components, desktop and web environment. We use the metadata to prevent 
components' conflicts with the target execution environment. Furthermore, 
we analyse the metadata at component deployment time to discover conflicts 
due to happen at runtime. That is, we propose an approach where conflicts 
arising from incompatible component's properties with the properties of the 
target execution environment and the properties of other components can be
statically predicted before runtime.