An architectural style defines as a family of such systems in terms of a (1) of structural organization. More specifically, an architectural style defines a vocabulary of (2) and connector types, and a set of (3) on how they can be combined. For many styles there may also exist one or more (4) that specify how to determine a system's overall properties from the properties of its parts. Many of architectural styles have been developed over the years. The best-known examples of (5) architectures are programs written in the Unix shell.
空白（2）处应选择（）
A.metadata
B.components
C.models
D.entities
