Entity structure for XML (Clause 6)
Despite Michael's request that messages be kept to a single subject within
the list I have decided not to bombard you all with one message per point I
want to make, but have tried to cover questions raised by one of the set of
forms in one posting. This set of points relates to dd-1996-0002-f2.html,
which deals with Entity Structure.
a) Should we allow SDATA entities as these require a system independent
translation? This might be acceptable if XML were to fix on one particular
notation, but would not generally be conducive to the receipt and display of
XML files by any browser with a suitable plug-in.
b) Should we predefine a set of NDATA notations that will be acceptable to
all browsers? What mechanism would there be for extending the list of
notations to take account of new developments in general support for a new
notation (e.g how will we allow for MPEG-4 in 2000)?
c) Should the use of subdocument entities be an option?
If you do not constrain parsing in a left-to-right manner how else would you
deal with the detection of nested marked sections? Do you just ban these?
Should we require that entity references end with a REFC code (the semicolon)?
On the question of SGML declaration transmission I feel that the current
text is in conflict with current practice. Most systems have an implied SGML
declaration, which is normally an extension of the one defined in 8879 that
is supposed to be used whenever you do not specifically receive one. WG8
have agreed in principle that it should be possible to identify a relevant
SGML declaration using a public (or system) identifier in the same way that
you can with a DocType declaration. This is the best long term solution. If
XML is to have a fixed SGML declaration then we have no problem. If, to suit
regional character set requirements, there is more than one option, there
should be a set of predefined SGML declarations that can be referenced via a
public identifier (perhaps through a PI or comment declaration) in front of
the DocType declaration.
Martin Bryan, The SGML Centre, Churchdown, Glos. GL3 2PU, UK
Phone/Fax: +44 1452 714029 WWW home page: http://www.u-net.com/~sgml/