W3C CSS2 Cascading Style Sheets, level 2 - instructional media + ...

Contents
Appendix D. The grammar of CSS2
D.1 Grammar . . . . . . . . . . . . . . 309 .
D.2 Lexical scanner . . . . . . . . . . . . . 311 .
D.3 Comparison of tokenization in CSS2 and CSS1 . . . . . 312 .
This appendix is normative.
The grammar below defines the syntax of CSS2. It is in some sense, however,
a superset of CSS2 as this specification imposes additional semantic constraints
not expressed in this grammar. A conforming UA must also adhere to the
forward-compatible parsing rules [p. 35] , the property and value notation [p. 14] ,
and the unit notation. In addition, the document language may impose restrictions,
e.g. HTML imposes restrictions on the possible values of the "class"
attribute.
D.1 Grammar
The grammar below is LL(1) (but note that most UA’s should not use it directly,
since it doesn’t express the parsing conventions [p. 42] , only the CSS2 syntax).
The format of the productions is optimized for human consumption and some
shorthand notation beyond Yacc (see [YACC]) is used:
*: 0 or more
+: 1 or more
?: 0 or 1
|: separates alternatives
[ ]: grouping
The productions are:
stylesheet
: [ CHARSET_SYM S* STRING S* ’;’ ]?
[S|CDO|CDC]* [ import [S|CDO|CDC]* ]*
[ [ ruleset | media | page | font_face ] [S|CDO|CDC]* ]*
;
import
: IMPORT_SYM S*
[STRING|URI] S* [ medium [ ’,’ S* medium]* ]? ’;’ S*
;
media
: MEDIA_SYM S* medium [ ’,’ S* medium ]* ’{’ S* ruleset* ’}’ S*
;
medium
: IDENT S*
;
page
: PAGE_SYM S* IDENT? pseudo_page? S*
’{’ S* declaration [ ’;’ S* declaration ]* ’}’ S*
;
309