Re: [xtm-wg] A challenge on ... PSI

[Murray Altheim <altheim@eng.sun.com>]

Bernard, 

I hate to tell you but I don't think there's much of a squirmish here. See
below.

Bernard Vatant wrote:
> 
> Since challenges are in the spring air, and since the graph war seems to
> calm down a little, giving back a little bandwidth to this list, I propose
> to open another battlefield ...
> 
> Below are some open questions about PSI. I've pushed some bits of reflection
> and questioning about it here and there, but would like some general
> feedback before putting together more formal propositions about it. On
> several of them, I've quite defined ideas as you can imagine, but let the
> questions open for the moment. Here goes a first salvo to declare the war
> :o) ... more to come I'm afraid !
> 
> 1. The notion of PSI is defined in the spec only in an informal way, and I
> would say in an external way: In short, a PSI is an URI you can refer as an
> indicator of the subject identity. Nowhere is written in a formal way what
> are the requirements - if any - about what should/must show at this URI to
> make it suitable for that use. I've already suggested that it has be
> clarified, for example:
> 
> - Is a PSI anything else that a neutral binding point, with no much more
> content than an address?

It's simply a URI intended by a topic map author to indicate subject. It
could be even a URN published in a paper-published trade journal. Publication
is left open because any particular community may have different notions of
publication. So long as the target community has been notified that a 
specific URI is intended to be stable (also a relative concept within a
particular community) and used as a PSI, that's all there is.

One might very well consider every word within a published version of the
Bhagavad Gita (accessed via XPath on a base URI) as a stable set of PSIs.
Resolution, DOI or URN resolution, and other features like URI extensions 
(such as queries following a "?") may make it difficult to resolve unless
one has specific tools. If an author either understands or expects their
community to have these tools, this is consistent with the TM metaphor.

> - If a PSI has a content, has it to be somehow Topic Map - like?

It doesn't have to have content. Resolving the PSI on the web *may* provide
information as to the subject, but if a specific community (let's say the
military) publishes a PSI privately within their community, perhaps as
above, only in print (with the descriptions also in print), then this is
publication, and the subject information has been provided. 

Constraining this is like trying to constrain the W3C namespace URI. It's
meant as an identifier.

> - Has a PSI content to be XTM conformant to be used in a XTM document?

No. If OTOH you wanted to make your PSIs more useful in a public forum
(say, the open Web), then resolving them to something most people could
read like XHTML would be recommended but not required.

> - Have PSI to be scoped? from the inside (editor-side)? from the outside
> (user-side)?

I don't understand how PSIs could be scoped intelligently without causing
problems. "This PSI means A on Wednesday, B on Thursday?"
 
> 2. The mandatory PSI in XTM 1.0 - independently of the controversial list of
> those who should or should not appear there, which is another pending
> question - are published under an "implicitly standardized" syntax. Is that
> syntax intended to become an explicit model for future extension of this PSI
> list? Is that syntax a suggestion or recommendation for other PSI editors,
> wishing to edit PSI repositories inside or outside the namespace
> topicmaps.org? See for example what's going on at http://psi.seruba.com/ or
> what Murray is working on about XTM and Cyc at
> http://www.doctypes.org/cyc/cyc-xtm-20010227.html, which I supposed is
> intended to be used as PSI repository ...

We published these PSIs as a topic map so that they would be functional
within a topic map system, so that no human would be required to read 
"what is at the other end" of the URI. I'd recommend anyone who wants
their PSIs to show up inside a topic map engine as part of the topic map
to do the same. But simply resolving to a web page, a URN, an ftp address,
whatever, it'd be a mistake to constrain this further, because we have
really no idea how far XTM might go, might be used. Restraining its
flexibility here doesn't sound like a good idea to me.

> 3. Is PSI a "pure XTM" concept, or could it be extended further into the
> "semantopic" universe? Have RDF, Dublin Core, PRISM, ebXML, NewsML, ISO
> standards, W3C recommendations etc ... something to do with/for/about PSI?
> Are there standardization approaches that look like PSI under other names,
> etc ...

We talked over chili about making the entire DMOZ directory system into
a series of PSIs.
 
> 4. Should topicmaps.org maintain some (un)official index of PSI
> repositories, or declare to be the (authoritative) source where PSI
> certification has to be found? Should that be normative or informative :o) ?

Eeueueuww. Much too totalitarian for my taste. Let a thousand orchids bloom...

> Well - think it's enough to begin with ... I've opened a 1 Go hard-drive
> space for your answers, hope it will do :)

I tried to keep it short. :-)

Murray

...........................................................................
Murray Altheim                            <mailto:altheim&#x40;eng.sun.com>
XML Technology Center
Sun Microsystems, Inc., MS MPK17-102, 1601 Willow Rd., Menlo Park, CA 94025

      In the evening
      The rice leaves in the garden
      Rustle in the autumn wind
      That blows through my reed hut.  -- Minamoto no Tsunenobu

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