Architecture, software architecture specifically, used to be only defined in terms of components, connectors and constraints per Shaw and Garlan.
However, it is increasingly evident to those of us who implement architectures on a daily basis for clients and internally within our own companies
that architecture requires the addition of composition, context and containers to make it operational.
Components -- what are the structural building blocks of a solution, or a style of architecture, of the elements that can be combined to produce a larger structure
§Composition -- How to compose or what are the valid compositions of components
§Connectors -- The components need to connect with one another, whether statically (as in an Entity-relationship kind of relation) or dynamically, as in a composition in an SOA, where you may have orchestration or choreography.
§Constraints -- The constraints on the connectors and/or components that provide rules of engagement of what is permissible and what is not.
§Context -- the context of invocation of a component is critical to the designation of how that component will behave
§Containers -- the components must live in some runtime container that will provide uniform life-cycle management capabilities for them