SyntaxNotation

We use a variant of EBNF (Extended Backus Naur Form) that is similar to regular expressions. We use a (slightly modified) subset of http://www.w3.org/TR/REC-xml/#sec-notation, the notation used by W3C to specify XML

Each rule in the grammar defines one symbol, in the form

symbol = expression we use the simpler =, like EBNF, whereas W3C uses ::=

An expression - the right hand side of a rule - may be

symbol a symbol which is defined as the left hand side of another or the same rule

"string" matches a literal string matching that given inside the double quotes.

'string' matches a literal string matching that given inside the single quotes.

These symbols may be combined to match more complex patterns as follows, where A and B represent expressions:

(expression) expression is treated as a unit and may be combined as described in this list.

A? matches A or nothing; optional A.

A B matches A followed by B. This operator has higher precedence than alternation; thus A B | C D is identical to (A B) | (C D).

A | B matches A or B.

A - B matches any string that matches A but does not match B.

A+ matches one or more occurrences of A. Concatenation has higher precedence than alternation; thus A+ | B+ is identical to (A+) | (B+).

A* matches zero or more occurrences of A. Concatenation has higher precedence than alternation; thus A* | B* is identical to (A*) | (B*).

Other notations used in the productions are:

(* ... *) comment. (as in EBNF, W3C uses /* ... */). Furthermore, wie use layout conventions for comments and rules like symbol = (* ... *) to describe a production that is easier defined in free text than by a formal syntax

Vergleich verschiedener Varianten von BNF

• my: wie oben definiert
• W3C in XML Definition: http://www.w3.org/TR/REC-xml/#sec-notation
• EBNF: http://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_Form
• BNF: http://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form

EBNF dagegen, hat einen expliziten KonkatinierungsOperator und verschiedenen Klammern für Multiplizitäten: