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The Microsoft code name "M" Modeling Language Specification - Languages

November 2009

[This content is no longer valid. For the latest information on "M", "Quadrant", SQL Server Modeling Services, and the Repository, see the  Model Citizen blog.]

 [This documentation targets the Microsoft SQL Server Modeling CTP (November 2009) and is subject to change in future releases. Blank topics are included as placeholders.]

Sections:
1: Introduction to "M"
2: Lexical Structure
3: Text Pattern Expressions
4: Productions
5: Rules
6: Languages
7: Types
8: Computed and Stored Values
9: Expressions
10: Module
11: Attributes
12: Catalog
13: Standard Library
14: Glossary

6 Languages

A language is a named collection of rules for imposing structure on text. 

syntax LanguageDeclaration

    = Attributes? "language" Name LanguageBody;

syntax LanguageBody

    = "{" RuleDeclarations? "}";

syntax RuleDeclarations

    = RuleDeclaration

    | RuleDeclarations RuleDeclaration;

The language that follows recognizes the single text value "Hello World":

module HelloWorld {

    language HelloWorld {

        syntax Main

          = "Hello World";

    }

}

6.1 Main Rule

A language may consist of any number of rules. The following language recognizes the single text value "Hello World":

module HelloWorld {

    language HelloWorld {

        syntax Main

          = Hello Whitespace World;

        token Hello

          = "Hello";

        token World

          = "World";

        token Whitespace

          = " ";

    }

}

The three rules Hello, World, and Whitespace recognize the three single text values "Hello", "World", and " " respectively. The rule Main combines these three rules in sequence. The difference between syntax and token rules is described in §5.1.

Main is the distinguished start rule for a language. A language recognizes a text value if and only if Main recognizes a value. Also, the output for Main is the output for the language.

6.2 Cross-language rule references

Rules are members of a language. A language can use rules defined in another language using member access notation. The HelloWorld language recognizes the single text value "Hello World" using rules defined in the Words language:

module HelloWorld {

       

    language Words {

        token Hello

          = "Hello";

        token World

          = "World";

    }

    language HelloWorld {

        syntax Main

          = Words.Hello Whitespace Words.World;

        token Whitespace =

          = " ";

    }

}

All rules defined within the same module are accessible in this way. Rules defined in other modules must be exported and imported as defined in §10.3.

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