Extrait de http://www.w3.org/TR/xml/#sec-logical-struct

[45]      elementdecl        ::=      '<!ELEMENT' S Name S contentspec S? '>'
[46]      contentspec        ::=      'EMPTY' | 'ANY' | Mixed | children
[47]      children           ::=      (choice | seq) ('?' | '*' | '+')?
[48]      cp                 ::=      (Name | choice | seq) ('?' | '*' | '+')?
[49]      choice             ::=      '(' S? cp ( S? '|' S? cp )+ S? ')'
[50]      seq                ::=      '(' S? cp ( S? ',' S? cp )* S? ')'
[51]      Mixed              ::=      '(' S? '#PCDATA' (S? '|' S? Name)* S? ')*' | '(' S? '#PCDATA' S? ')'

[52]      AttlistDecl        ::=      '<!ATTLIST' S Name AttDef* S? '>'
[53]      AttDef             ::=      S Name S AttType S DefaultDecl
[54]      AttType            ::=      StringType | TokenizedType | EnumeratedType
[55]      StringType         ::=      'CDATA'
[56]      TokenizedType      ::=      'ID' | 'IDREF' | 'IDREFS' | 'ENTITY' | 'ENTITIES' | 'NMTOKEN' | 'NMTOKENS'
[57]      EnumeratedType     ::=      NotationType | Enumeration
[58]      NotationType       ::=      'NOTATION' S '(' S? Name (S? '|' S? Name)* S? ')'
[59]      Enumeration        ::=      '(' S? Nmtoken (S? '|' S? Nmtoken)* S? ')'
[60]      DefaultDecl        ::=      '#REQUIRED' | '#IMPLIED' | (('#FIXED' S)? AttValue)

[61]      conditionalSect    ::=      includeSect | ignoreSect
[62]      includeSect        ::=      '<![' S? 'INCLUDE' S? '[' extSubsetDecl ']]>'
[63]      ignoreSect         ::=      '<![' S? 'IGNORE' S? '[' ignoreSectContents* ']]>'
[64]      ignoreSectContents ::=      Ignore ('<![' ignoreSectContents ']]>' Ignore)*
[65]      Ignore             ::=      Char* - (Char* ('<![' | ']]>') Char*)

[66]      CharRef            ::=      '&#' [0-9]+ ';' | '&#x' [0-9a-fA-F]+ ';'
[67]      Reference          ::=      EntityRef | CharRef
[68]      EntityRef          ::=      '&' Name ';'
[69]      PEReference        ::=      '%' Name ';'
[70]      EntityDecl         ::=      GEDecl | PEDecl
[71]      GEDecl             ::=      '<!ENTITY' S Name S EntityDef S? '>'
[72]      PEDecl             ::=      '<!ENTITY' S '%' S Name S PEDef S? '>'
[73]      EntityDef          ::=      EntityValue | (ExternalID NDataDecl?)
[74]      PEDef              ::=      EntityValue | ExternalID

[75]      ExternalID         ::=      'SYSTEM' S SystemLiteral | 'PUBLIC' S PubidLiteral S SystemLiteral
[76]      NDataDecl          ::=      S 'NDATA' S Name
[77]      TextDecl           ::=      '<?xml' VersionInfo? EncodingDecl S? '?>'
[78]      extParsedEnt       ::=      TextDecl? content
[80]      EncodingDecl       ::=      S 'encoding' Eq ('"' EncName '"' | "'" EncName "'" )
[81]      EncName            ::=      [A-Za-z] ([A-Za-z0-9._] | '-')*