| At 16:37 2000 11 21 -0800, Terry Allen wrote:
| >| | You can always make a URL or URN for "the latest version
| >| | of foo", though I don't know that it would be real useful for
| >| | XML.
| >|
| >| I use it all the time. The URI
| >| http://nwalsh.com/xsl/docbook/html/docbook.xsl always points to the
| >| most recent version of the DocBook stylesheets.
| >
| >But you wouldn't want to do that with DTDs
|
| Maybe I'm misunderstanding the details here, but something like
| this is one of *the* most common uses of a catalog for me.
|
| Specifically, I have lots of documents with a doctype decl of:
|
| <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.1//EN"
| "http://www.oasis-open.org/docbook/xml/4.1.1/docbookx.dtd">
Naming and locating a particular version.
| or
|
| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
| "http://www.w3.org/TR/xhtml1/DTD/transitional.dtd">
Naming and locating a particular version.
| and then along comes the next upward-compatible version of the
| doctype. I install the latest doctype and usually toss the older
| version (because maintenance of two versions is costly and unnecessary).
| Newly created documents will use the new doctype decl, but the existing
| documents remain unchanged--and I want both to use the new doctype (dtd).
But if the new DTD has backward-incompatible changes, your old
documents may not parse against it. That was my point, complicated
slightly by the detour through style sheets.
| My existing catalog would look something like (whether the right hand
| sides point via HTTP to the official DTD copies or to a local cache is
| irrelevant for the purposes of this discussion):
|
| PUBLIC "-//OASIS//DTD DocBook XML V4.1.1//EN"
| "doctypes/docbook411/docbookx.dtd"
| PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
| "doctypes/xhtml10.dtd"
|
| After installing the new doctype and tossing the old one, I change
| my catalog to look something like:
|
| PUBLIC "-//OASIS//DTD DocBook XML V4.1.1//EN"
| "doctypes/docbook412/docbookx.dtd"
| PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
| "doctypes/xhtml-11.dtd"
|
| PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
| "doctypes/docbook412/docbookx.dtd"
| PUBLIC "-//W3C//DTD XHTML 1.1 Transitional//EN"
| "doctypes/xhtml-11.dtd"
|
| and I'm all set. Both old and new documents--regardless of the
| doctype decl--use the latest doctype. We do this constantly with
| doctypes--both our own and public ones (e.g., HTML, XHTML, DocBook)
| in the Arbortext standard distribution.
For Docbook this should work for minor releases, but it is not
guaranteed to work for major releases.
regards, Terry
