In a composition model for large-scale extensible applications, applications are constructed in a modular fashion. The modules integrate with each other by producing and consuming functionality that conforms to a common definition. Producer modules and consumer modules are kept independent of one another, and are linked together indirectly via a definition module. .NET attributes are used to identify various code artifacts (such as classes, methods, properties, etc.) as being functionality definitions, productions, and/or consumptions. These attributes are examined by the module loader and used to create relationships between individually installed producer and consumer modules. The consumer uses .NET attributes to declare dependency on functionality and filter out implementations that don't meet the criteria specified by those attributes.