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work in progress on dual-use theory

From: Jonathan Rees <jar@creativecommons.org>
Date: Fri, 21 Jan 2011 15:14:32 -0500
Message-ID: <AANLkTikYWPG5bJx115QL-nQ_b2L1RA2tSF-Wfh=Bwwq9@mail.gmail.com>
To: AWWSW TF <public-awwsw@w3.org>
So I'm making a model of the web in which all info-resources are
'fixed resources' (Tim's term).  I figure that if we can't spin a solid
story around this, the whole enterprise is hopeless.  I think the following
is pretty good, except for a gaping hole (inconsequential I think)
around exactly which resource is 'at' a URI. This goes back to our
'phlogiston' discussion.

Without 'phlogiston' the theory becomes immensely simpler, but TimBL
has imposed this as a requirement and shown little flexibility around it.


Term: 'directive' (class)
  Def: Information supplied in addition to content that is
  intended to direct the interpretation of the content.  Content-type
  header or equivalent, content-language or equivalent, perhaps
  others.  (Expires: header??)
  Definition source: invention of JAR
  Similar to: metadatum, HTTP entity header

Term: 'fixed resource' (class)
  Def: Content + directives, produced through some real process
  but with identity generic across physical incarnation.  I.e. it can
  be incarnated in multiple locations (disk drives, etc), each of
  which might be said to hold a copy of the fixed resource.
  Definition source: TimBL genont

Term: 'representation' (class)
  Def: Similar to 'fixed resource' but independent of provenance.
  That is, the identity of a 'representation' is determined by the
  content and directives.  In case two processes coincidentally result
  in the same content and media type, we would say there are two fixed
  resources but that the two fixed resources 'have' the same
  Similar to: RFC 2616 'entity', AWWSW 'representation'

  Note: JAR and Pay Hayes both oppose making a distinction betwen
  fixed resource and representation.  The distinction is included at
  TimBL's insistence.

Term: 'has fixed representation' (property)
  Domain: fixed resource
  Range: representation
  Def: The representation is a projection of the fixed resource,
  i.e. shares its content and directives.

Term: 'is authorized for' (data property)
  Domain: 'representation'
  Range: URI (xsd:anyURI)
  Def: The agent that legitimately controls the URI (its "owner")
  authorizes the representation for inclusion in an HTTP 200 response
  to a GET request with the URI as target URI.
  Definition source: HTTPbis part 1 section 2.6.1

Term: 'is served fixedly from' (data property)
  Domain: 'fixed resource'
  Range: URI
  Def: R is served fixedly from U iff R's representation is the only
  representation authorized for U.
  Similar to: log:URI ?

  Note: 'is served fixedly from' is not functional under this definition.  If
  R is served fixedly from U then so is any fixed resource S that has
  the same representation.

Now we can stipulate that fixed resources, or at least some of them,
can act as subjects of metadata, by interpreting the content
(as modulated by the directives) appropriately.  In particular:

- RDFS - can participate in rdfs:seeAlso, rdfs:isDefinedBy, etc.
- FOAF  - every fixed resource is a foaf:Document, so can participate
  in foaf:homepage, foaf:topic, etc.
- Dublin Core  - fixed resources can have dc:creators, etc.
- CC REL - some fixed resources are legally protected by copyright
   and can be licensed (xhtml:license property)

We can express a form the httpRange-14 rule:

  When exactly one representation is authorized for U,
  (a) everyone is urged to use U to name only some particular fixed
  resource served fixedly at R (which one is not clear, but probably
  depends on the process by which it was created or chosen by U's
  (b) absent information about which fixed resource is involved,
  just assume that U names some unknown fixed resource served fixedly
  at R.


Generalizing beyond fixed resources.  I still don't know how to do
this in a way that meets all requirements (in particular the 'Moby
Dick is an IR' requirement and the 'every web page is an IR'

Term: 'information resource' (class)
  Has subclass: 'fixed resource'
  Def: Some nontrivial generalization of fixed resource, i.e. bigger
  than fixed resource but smaller than rdf:Resource.  TBD.

Term: 'has representation' (object property)
  Has subproperty: 'has fixed representation'.
  Def: 'Has fixed representation' is the restriction of 'has
  representation' to fixed resources.
  Otherwise, definition is still a mystery to JAR; definition to be
  determined later in the investigation, one hopes.  Please be

Term: 'is served from' (data property)
  Has subproperty: 'is served fixedly from'
  Range: URI
  Def: R is served from U iff R's representations are exactly the
  ones authorized for U.

Use of metadata properties with information resources generally is
more complicated than with fixed resources; I have proposed the
universal quantification rule which would apply to RDFS, FOAF, DC, CC
REL, etc.

httpRange-14 I think will generalize from the version given earlier,
as all of its annoyances are already surfaced with fixed resources.

In a universe in which httpRange-14 does not hold, one could add

  awwsw:isServedFrom "http://example.com/document1"^^xsd:anyURI .

to help clarify what it is one means by using that URI.  (Of course
one could use a different URI, or a blank node, to name the IR
Received on Friday, 21 January 2011 20:15:00 UTC

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