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.
（2）是（）
A. metadata
B. components
C. models
D. entities