XFN Backus-Naur Form (BNF)
The following defines the standard string form of XFN composite names in Backus-Naur Form (BNF). All the characters of the string representation of one name must uniformly use the same encoding and locale information. The notations used are shown in Table B-1:
Table B-1 Backus-Naur Notation
|
Symbol
|
Meaning
|
|
::=
|
Is defined to be
|
|
|
|
Alternatively
|
|
<text>
|
Nonterminal element
|
|
`' `'
|
Literal expression
|
|
*
|
The preceding syntactic unit can appear 0 or more times.
|
|
+
|
The preceding syntactic unit can appear 1 or more times.
|
|
{}
|
The enclosed syntactic units are grouped as a single syntactic unit (can be nested).
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The XFN composite name syntax in BNF is shown in Table B-2:
Table B-2 XFN Composite Name Syntax Using BNF
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XFN Composite Name
|
BNF Syntax
|
|
NULL ::=
|
// Empty set
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|
<PCS> ::=
|
// Portable Character Set.
The set consists of the glyphs:
//!"#$%&'()*+,\0123456789:;<=>?
//@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_'
//abcdefghijklmnopqrstuvwxyz{|}~
|
|
<CharSet> ::=
|
<PCS>
| Characters from the repertoire of a string representation
|
|
<EscapeChar> ::=
|
\
|
|
<ComponentSep>::=
|
/
|
|
<Quote1>::=
|
"
|
|
<Quote2> ::=
|
`
|
|
<MetaChar> ::=
|
<EscapeChar> | <ComponentSep>
|
|
<SimpleChar> ::=
|
// any character from <CharSet> with <MetaChar>, <Quote1>,
// and <Quote2> excluded. An<EscapeChar> <MetaChar>, or
// <EscapeChar> <Quote1>, or <EscapeChar> <Quote2> is equivalent to
// <SimpleChar>.
|
|
<Component> ::=
|
<SimpleChar>*
| <SimpleChar>+ {<Quote1> | <Quote2> | <SimpleChar>}*
| <Quote1> <CharSet>* {<EscapeChar> <Quote1>}* <Quote1>
// <CharSet> must not contain unescaped <Quote1>
// (note that <Quote2> can appear unescaped)
| <Quote2> <CharSet>* {<EscapeChar> <Quote2>}* <Quote2>
// <CharSet> must not contain unescaped <Quote2>
// (note that <Quote1> can appear unescaped)
|
|
<CompositeName> ::=
|
NULL
| <Component> {<ComponentSep> <Component>}*
|
