[tei-council] MD chapter revised: namespace rules

[Lou Burnard]

Sebastian Rahtz wrote:
 > Dan O'Donnell wrote:
 >> But do you Sebastian? If you think Sugar is not a namespace issue,
 >> surely you think it needs to be undoable for interchange?
 >>
 > I *still* haven't gone to bed, and I admit that
 > I am backing myself slowly into an interchange corner.....
 >
 >
I, on the other hand, did go to bed at a sensible time, and thus have 
had the opportunity to sleep on it.

Let me try to reformulate the issues here:

1. "Conformance" means, fundamentally, conformance to the TEI abstract 
model. The markup scheme defined by or applied in a TEI conformant 
document marks up abstract concepts which are also present in the TEI 
abstract model, and with the same meaning.

2. The particular part of the TEI abstract model which a set of document 
uses can be expressed in three ways, only two of which can be 
automatically checked:

a) the application of the elements is something that a human reader 
recognizes as plausible i.e. the thing tagged <l> does actually contain 
a line of verse

b) particular things are called by particular names i.e. the thing 
containing a line of verse is called <l> (in the TEI namespace) and not 
<line>.  Namespaces are a useful way of asserting whether the "l" here 
is the TEI "<l>" or some other one.

c) TEI syntactic rules are respected e.g. <l>s appear inside <div>s but 
not vice versa. Validating this is what schemas are for.

3. Modification/customization/personalization is something we do in 
order to generate and document a schema, so it is about both (a) and 
(c). A modification which replaces the <desc> of <l> to say that it is 
for typographic lines is an unclean one, as is one which modifies its 
content model to permit <div>s within it -- in the same way   and for 
the same reasons. Only "clean"[1] modifications are conformant (this 
doesnt mean that unclean modifications are evil, just that they are 
different. Most improvements to the TEI scheme start off life as unclean 
modifications.)

4. We are disagreeing about whether or not a modification which is a 
simple renaming is unclean, i.e. about whether 2(b) is somehow different 
from the other kinds of conformance constraint. I can identify the 
following reasons for this disagreement:

  i/ We are so used to seeing different names for the same thing that it 
just doesn't seem important to insist on using a specific name, or to 
insist that names declare their namespace. (cf the pain of going from 
case-insensitive to case-sensitive identifiers which some of us old'uns 
are still suffering from).

ii/ We think many people will find namespace technology a step too far 
and that this fear will lead them (or us) into all manner of folly

iii/ We know how to easily convert document instances which use renaming 
into ones which don't (whereas conversion of other kinds of uncleanly 
modified documents is in general problematic or impossible)

iiii/ We (or me at least) are not quite sure how to support extra 
namespaces for renaming modifications with the current tool kit

v/ Namespaces are just not the same kind of constraint as schemas -- in 
particular they are open-ended: any element can assert that it belongs 
to a given namespace and the assertion cannot be validated


Of these I think all but iii are fairly weak. If we take iii seriously 
though, maybe what it shows is that we do need an extra concept. We have 
previously spoken about "conformance" and "interchange format" and 
havered somewhat about the distinction between the two. Maybe what we 
need instead is a concept of "canonical representation".

How about this as a compromise:

A conformant TEI document can take either of two forms

* local form -- in which ODD-documented renamings are permitted to join 
the TEI namespace
* canonical form -- in which ODD-documented renamings must either be 
converted to their equivalent TEI form, or must be assigned to some 
other namespace

Probably enough to be going on with, but I would appreciate some 
indication of where in this diatribe you stopped saying "yeah yeah we 
know that"


L


[1] "clean" as defined in the current draft for MD