Re: Discussion of entities
On Mon, 23 Sep 1996 22:14:16 -0700, bosak@atlantic-83.Eng.Sun.COM (Jon Bosak)
>To all who heeded my request to hold off discussing entities for a few
>days: Thank you. Well-known figures in the SGML field have compared
>this kind of job to herding cats, but for a bunch of notorious
>individualists you are proving to be a wonderfully cooperative group
Here is a complete proposal for entities. I think it has the virtue of
identifying all of the options we have, so we can decide whether we like or
dislike each one. It also has the virtue of correcting the many errors in
previous postings on entities.
Default entities are not permitted.
Internal entities defined with "data text" or "bracketed text" are not
permitted. Other internal entities are the same as for full SGML.
There are three issues to resolve in external entity management for XML:
1. Types of entity text
XML(SGML) text entities are permitted. They are accessed and parsed *in context*
by the XML parser.
CDATA, SDATA, and NDATA data entities are permitted. Any data content notation
can be used. The entities are accessed and processed at the discretion of the
XML(SGML) SUBDOC entities are permitted. They are accessed and parsed *in their
own context* at the discretion of the application.
XML(SGML) document entities are CDATA entities declared with the XML(SGML)
notation. They are accessed and parsed *in their own context* at the discretion
of the application.
2. Forms of reference
XML(SGML) text entities are referenced by a parameter entity reference or a
general entity reference.
Data entities, XML(SGML) SUBDOC entities, and XML(SGML) document entities are
referenced only by attribute values, not by general entity references.
3. Forms of address
Entities can be declared with PUBLIC ids or Formal System IDs, but not with
omitted system identifiers.
PUBLIC ids are resolved using the SGML Open catalog with Formal System IDs on
the "right side" of the catalog entries.
The set of storage managers and attributes allowed in FSIs (in both declarations
and catalog entries) is for further discussion. Some obvious candidates are URL
Charles F. Goldfarb * Information Management Consulting * +1(408)867-5553
13075 Paramount Drive * Saratoga CA 95070 * USA
International Standards Editor * ISO 8879 SGML * ISO/IEC 10744 HyTime
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