[topicmapmail] PPJTM

[Murray Altheim]

Patrick Durusau wrote:
> Max,
> 
> Max Voskob wrote:
> 
>> Peter,
>>
>> Would you consider publishing XML Schema instead of DTD?
>> It would be a step forward ...

...towards a cliff?

> As well as a step away from the DTD! ;-)

Now, now. Stop beating up on the poor DTD. One might note that
there are various *reasons* for choosing a schema language. If your
need is to create a validation or constraint tool, you look at the
kinds of constraints and find the simplest and most understood mechanism
available. If you're trying to design a syntax and tell other people
about it, you choose an expression that is easy to read (probably
*not* in XML syntax) and well-understood. If your predominant interest
is machine validation, certainly the alternatives work, though you
might yourself have a tough time on complex content models being sure
you've actually designed the model you think you have.

Now, if you really want to follow fashion, XML Schema or RELAXNG
will buy you some cachet, but at the expense of anyone being able
to easily read it. DTD content models are about as easy to read as
anything. (If they're obscured by lots of parameter entities, its
a simple matter to run the DTD through a normalizer.) Tools that
convert schemas to web pages are quite helpful here too. A ton
of people have perused the HTML DTDs, more probably than any other
DTD in history. I'd challenge a headcount on any other schema
language being as well known on this basis alone, much less the
length of time each schema language has been around. And DTD-based
validation is built into every one of the major XML parsers out
there, whereas XML Schema is only in a few and RELAXNG (to my
knowledge) requires a separate tool. Sun has published a multi-
schema validator that handles all three, though last time I checked
it still had a few bugs. Not bad though considered it was written
by one guy (who we locked in a closet until he was done).

I've got a pretty good handle on all three SGML/XML schema languages
and still prefer DTDs when designing languages because I know that
they're stable and better understood than the alternatives. When I
need further constraints I prefer RELAXNG, but I think to some degree
one must consider the target audience and real purpose in publishing
a schema, not simply do jump on some bandwagon.

> NOTE: The following is not legal advice! Just observations about DTDs 
> and what I have or have not heard about in the past.
> 
> Don't think I have ever seen copyright litigation from the first person 
> to use and copyright <p></p>.  I have not seen any copyright litigation 
> over element GIs at all. Doesn't mean that it has not happened, just 
> that I have never seen it.
> 
> Come to think of it, I have never seen the first person to put <q></q> 
> inside of <p></p> sue for content model infringement.

Well, now that I'm in England I suppose I should bone up on UK copyright
law, since I don't know much about it here.

But I do know a fair amount about copyright law in the US, despite playing
a lawyer (and brain surgeon) only on TV. So here follows a whole lot of
hot pseudo-legal air (if I'm not known for that by now...).

Copyright does not protect ideas, only things such as images,
documents and other types of unique and identifiable expressions.
By simply putting a copyright statement (i.e., "Copyright" and/or
the copyright symbol plus your name and a date) you have (in the US)
effectively copyrighted your work. You don't need to register it with
the US Copyright Office, though if you're really interested in doing
so, this can be done. I went to the trouble years ago, sending issues
of my cartoons as published, which was a lot of trouble. It didn't
garner me any extra protection AFAIK. Somewhere in some DC warehouse
is a stack of really yellow newspapers that nobody will ever see (just
as well).

If you want to protect ideas, you must patent them. I know of nobody
who's ever patented the kinds of things in a schema, though certainly
if there was something entirely unique idea-wise you could attempt to
do so. It's very expensive and you need to go through some measure of
prior-art demonstration. Since most schemas are based heavily upon
other schemas (at a fairly profound level in most cases I've ever
seen) I don't see how anyone could patent a schema. Software code is
a bit different because you can patent algorithms.

Generally, DTDs, schemas, and computer code of any kind are considered
as documents and can be copyrighted as can any document. You can include
a license statement within the document that states usage and liability,
which is a good idea, since if you don't you could in theory be sued if
for any reason somebody lost money using your document or software. When
I started writing DTDs I basically took the copyright statement from the
DocBook DTD and modified it to suit. Over the years everything I've heard
has suggested that the text I use now (which is the text found in the XTM
1.0 DTD as well) is a suitable copyright, license and limit of liability
statement.

There is plenty of legal precedent for plagiarism, which you might be
accused of if you were to take an existing DTD and merely change the
whitespace or parameterization. IMO this will come down a lot to what
the license on the schema says. Most every one I've seen has a limit
of liability protecting the owner but essentially gives up any
protections in order to explicitly allow people to use the
document in any way so long as they don't misconstrue the authorship.
The TopicMaps.Org XTM 1.0 DTD has this statement, which mimics that
of DocBook, HTML and XHTML.

Now, the ISO XTM DTD is another matter. It's published as part of an
ISO/IEC-copyrighted document, hence it's protected by whatever license
is granted that document. The ISO document doesn't include "All Rights
Reserved" nor does it include the year, so AFAIK it's not in strict
conformance with US copyright law, though I don't think anyone would
challenge ISO on that one. Interestingly enough, there are no copyright
statements whatsoever on the DTD within the document, which I would
expect might be passed around outside of the standards document, so
I'm not sure if this was an oversight or by plan. (Jim?)

The thing about anything legal is that if you as a mere individual go
up against a large corporation, it seems like the general tactic is
to simply wear you down so that you'll either give up or, if you
actually have a case to be made, you'll settle out of court. I have a
friend who is an inventor of sorts, and he basically was forced to
quit working on an idea because a large corporation caught wind of
his work and shut him down, claiming they had a patent in the area
he was working. He actually got a cease-and-desist notice via
registered mail, very official-looking. He was told it would cost him
a minimum of something crazy like $50,000 to fight it. Point is, all
the legal protection in the world won't do you much good (right or
wrong) if you're up against big money.

My $0.04. (legal advice even from non-lawyers don't come cheap)

Murray

...........................................................................
Murray Altheim                         http://kmi.open.ac.uk/people/murray/
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK                    .

     Why is it that they impeached Clinton when he lied about having sex
     with a consenting adult, but they aren't talking about impeaching
     Bush over having led the world into war by lying about the presence
     of WMDs in Iraq? Is the US more squeamish about sex than war?