Analysis of a conflict between aggregation and interfacenegotiation in Microsoft's Component Object Model

摘要

Many software projects today are based on the integration ofnindependently designed software components that are acquired on thenmarket, rather than developed within the projects themselves. Ancomponent standard, or integration architecture, is a set of designnrules meant to ensure that such components can be integrated in definednways without undue effort. The rules of a component standard define,namong other things, component interoperability and compositionnmechanisms. Understanding the properties of such mechanisms andninteractions between them is important for the successful developmentnand integration of software components, as well as for the evolution ofncomponent standards. The paper presents a rigorous analysis of two suchnmechanisms: component aggregation and dynamic interface negotiation,nwhich were first introduced in Microsoft's Component Object Model (COM).nWe show that interface negotiation does not function properly within COMnaggregation boundaries. In particular, interface negotiation generallyncannot be used to determine the identity and set of interfaces ofnaggregated components. This complicates integration within aggregates.nWe provide a mediator-based example, and show that the problem is in thensharing of interfaces inherent in COM aggregation