ERB discussion of public identifiers
We spent a lot of time on this question on Dec. 11th, and it is clear we
need some more help from the WG.
The ERB is, by at least a substantial majority, convinced that there is a
real nead for PUBLIC identifiers in XML.
The ERB is highly concerned, in at least a significant minority, about
the effects of putting this facility in without specifying a resolution
mechanism. Doing so would contravene one of the major design goals of
XML - that any compliant XML processor should be able to read any compliant
On the other hand, there is also substantial concern about giving an
unconditional blessing to any particular name resolution mechanism at
this point in history.
Thus, there are a variety of options open to us.
1. Leave it as it is
2. Agree that we'll put PUBLIC identifiers into XML *when* we are ready
to specify the resolution mechanism; the practical effect is almost
certainly that they don't go in for now.
3. Put a slot in the syntax for PUBLIC identifiers...
3* ...and require an accompanying SYSTEM identifier
3a - say nothing about resolution mechanisms, perhaps providing a
taxonomy of available technologies in this area
3b - document one resolution mechanism, but not make it required.
This is somewhat similar to our i18n approach, where we bless 2
encodings but admit the possibility that people use others.
3c - document one resolution mechanism as before, but make its use
mandatory for XML processors.
Note that there is a continuum between 3b and 3c; we could place
varying strengths of recommendation behind one resolution mechanism,
with homilies about document portability.
In the area of which resolution mechanism to (perhaps nonexclusively)
bless, SGML/Open catalogs (hereinafter Socats) stand out, and would
probably be the ERB's choice. On another hand, there has been a lot
of work go into the URN effort; on another hand, that work has not yet
born practical fruit in terms of ubiquitous implementations; on another
hand, the FPI syntax is repellent to some and it is not clear how well
it supports internationalization; on another hand, it may be the case
that FPI's really are URN's as they stand.
I suspect that if a binding vote were taken today, the ERB would either
(a) reinstate the PUBLIC keyword, and put in a nonexclusive recommendation
for Socat support, or
(b) refuse to put PUBLIC in until there was agreement on a required
Cheers, Tim Bray
email@example.com http://www.textuality.com/ +1-604-488-1167