XML Companion, The, Third Edition

Entities for characters

Until the more advanced character set schemes described above become widely used in operating systems and transfer media, many users of XML may prefer to continue to work with 7-bit ASCII, and rely upon entities to describe additional characters. Many XML DTDs, for example, contain references to ISO entity sets:

<!ENTITY % ISOlat1 PUBLIC "ISO 8879:1986//
           ENTITIES Added Latin 1//EN"
           SYSTEM "../ISOlat.ent">
<!ENTITY % ISOgrk1 PUBLIC "ISO 8879:1986//
           ENTITIES Greek Letters//EN"
           SYSTEM "../ISOgrk.ent">

%ISOlat1; %ISOgrk1;

However, it is perhaps too easy just to add entity declarations that refer to the ISO sets. An ISO set may be added because it contains a few (or even just one) required character definitions. But, once ...