8 Architectural Constructs

This chapter indicates the abstract and  [DELETED]concrete syntax of the constructs of architectural specifications, and describes their intended interpretation, extending what was provided for basic and structured specifications in Parts I and II.

      ARCH-SPEC-DEFN ::= arch-spec-defn ARCH-SPEC-NAME ARCH-SPEC
      ARCH-SPEC      ::= BASIC-ARCH-SPEC | ARCH-SPEC-NAME

An architectural specification definition ARCH-SPEC-DEFN is written:

arch spec

ASN =

ASP

end

It defines the name ASN to refer to the architectural specification ASP, extending the global environment (which must not already include a definition for ASN). The local environment given to ASP is empty.

      ARCH-SPEC-NAME ::= SIMPLE-ID

An architectural specification name ARCH-SPEC-NAME is normally displayed in a SMALL-CAPS font, and input in mixed upper and lower case.

A reference in an architectural specification ARCH-SPEC to an architectural specification named ASN is simply written as the name itself `ASN'. It refers to the the current global environment, and is well-formed only when the global environment includes an architectural specification definition for ASN. The enclosing definition then merely introduces a synonym for a previously-defined architectural specification.

      BASIC-ARCH-SPEC ::= basic-arch-spec UNIT-DECL-DEFN+ RESULT-UNIT
      UNIT-DECL-DEFN  ::= UNIT-DECL | UNIT-DEFN
      RESULT-UNIT     ::= result-unit UNIT-EXPRESSION

A basic architectural specification BASIC-ARCH-SPEC is written:

units UD₁; ... UD_n; result UE;

It consists of a list of unit declarations and definitions UD₁, ..., UD_n, together with a unit expression UE describing how such units are to be composed. A model of such an architectural specification consists of a unit for each UD_i, and the composition of these units as described by UE.