>Also the URI mechanism has all that is needed to
>distinguish resources from identities. (01)
What? Please explain. Are you assuming a
distinction between two kinds of things, called
"resources" and "identities"? This is getting
less and less comprehensible. Please explain what
you mean by these words, or give an example. (02)
>For some reason we tend to use the web protocol
>"HTTP" where as this makes no sense for a pure
>identity. (03)
What makes an identity pure?? (04)
>We could substitute any protocol name in a
>URI to distinguish logical resources, such as:
>
>"identity://cim3.net/MyCat" (A pure identity)
>Vs.
>"<http://www.cim3.net/CIM3_Executive_Brief_files/frame.htm>http://www.cim3.net/CIM3_Executive_Brief_files/frame.htm";
>
>(A real resource)
>
>While there is no standard for "identity" it can
>be used without a problem since we are not
>expecting to utilize it as an internet protocol. (05)
This reasoning is very dangerous, since we are
now using internet protocols to communicate
assertions and queries which *refer to* resources
in ways that may not use a URI. Questions of
identity are central to the semantics underlying
the reasoners which process these assertions and
queries. (06)
Pat (07)
>
>
>From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx]
>On Behalf Of Ken Laskey
>Sent: Friday, April 13, 2007 7:27 PM
>To: edbark@xxxxxxxx
>Cc: [ontolog-forum]
>Subject: Re: [ontolog-forum] {Disarmed} Re: OWL and lack of identifiers
>
>Just to be clear, from RFC 2396:
>
>A Uniform Resource Identifier (URI) is a compact string of characters
>for identifying an abstract or physical resource.
>
>A resource can be anything that has identity. Familiar
>examples include an electronic document, an image, a service
>(e.g., "today's weather report for Los Angeles"), and a
>collection of other resources. Not all resources are network
>"retrievable"; e.g., human beings, corporations, and bound
>books in a library can also be considered resources.
>
>
>Thus, anything that can be identified is a
>resource (i.e., you can use everything for
>something) and URIs are one means (and one that
>has been found very useful) for providing that
>identity.
>
>Ken
>
>
>On Apr 13, 2007, at 3:10 PM, Ed Barkmeyer wrote:
>
>>Ken Laskey wrote:
>>
>>>>When the URI is a reference to a Web page
>>>>(full stop), the resource is the web page,
>>>>and by extension, the information content of
>>>>the web page.
>>>>
>>>I think of the page and its information content as being separate.
>>>
>>
>>From an ontological point of view, I may also
>>want to distinguish the content from its
>>external representation, if that was your
>>point. But the Web does not make that
>>distinction. Put another way, the Web
>>consciously manages external representations of
>>information, and leaves the abstraction of
>>content to the reader. The whole idea of the
>>Semantic Web is to provide standard external
>>representations for some orderly abstraction of
>>content, in order to facilitate search.
>>
>>I find it important to distinguish the location
>>of the information from its content, which was
>>my point. So perhaps we are talking past each
>>other.
>>
>>But the definition of URI (IETF RFC 2396) says it identifies a "resource".
>>
>>>For example, I can make statements about the
>>>style of the page display, the server where
>>>the <html> tags reside, the provenance
>>>information for the page. These are all
>>>separate from the information content of the
>>>page.
>>>
>>
>>We have now identified several distinguishable concepts:
>>1) the place
>>2) the presentation structure (web page)
>>3) the information content
>>4) a formal description of the content
>>5) the "provenance metadata" for the content
>>6) the provenance metadata for the presentation
>>7) the provenance metadata for the presentation in that place
>>
>>And we could easily make a model (ontology) for
>>these things and their relationships:
>>place(1) conveys presentation(2)
>>presentation(2) conveys content(3)
>>content(3) has formal description(4)
>>content(3) has provenance of content(5)
>>presentation(2) has provenance of presentation(6)
>>place(1) has provenance of site content(7)
>>
>>Further we note that there are other possibilities. In particular,
>>place(1) provides service(8)
>>service(8) permits access to presentation(2)
>>
>>RFC 2396 is pretty clear that a URL identifies
>>a place(1) full stop, and indicates a means of
>>access to whatever is at that place. From our
>>would-be ontology above, what is thus addressed
>>is either a presentation/document or a service.
>>
>>By comparison, RFC 2396 says that a URI
>>identifies a "resource". And all of
>>(2),(4),(5),(6),(7) and the service (8) are
>>distinct resources that may be found at the
>>*same site*. (I think the Web view is that
>>content(3) is only accessible through its
>>presentation(2).) It follows that each of them
>>should have a distinct URI. Those URIs may be
>>distinct URLs in their own right, or they may
>>all incorporate a common URL and each have a
>>distinct fragment identifier.
>>
>>Since a URL always identifies a place, if the
>>distinct resources have distinct URLs, our
>>model above needs some additions:
>>place(1) conveys formal description(4)
>>place(1) conveys provenance of content(5)
>>place(1) conveys provenance of presentation(6)
>>place(1) conveys provenance of site content(7)
>>
>>One place can convey some or all of
>>(2),(4),(5),(6),(7),(8), but when one place
>>conveys more than one of them, each has a
>>distinct URI whose "fragment identifier"
>>distinguishes the "component". And by
>>convention, in those cases, the URI with no
>>fragment identifier (the simple URL) conveys
>>either (2) or (8). It is also possible that we
>>have a (9), which is a web page that is a
>>container for (2),(4),(5),(6),(7), delivered as
>>a single resource.
>>
>>Note that our model is starting to get rather messy.
>>This is why Tim Burners-Lee says you need to
>>impose some discipline on your site. The
>>problem is that several different conventions
>>have emerged (including not imposing any
>>discipline), and there are no reference
>>standards.
>>
>>In a somewhat different vein, I wrote:
>>
>>>>I have argued with TBL before that URIs that
>>>>are URLs confuse WHAT something is with WHERE
>>>>it is. And it is only an acceptable idea when
>>>>that relationship is required to be 1-to-1.
>>>>The idea of identifiers is that you can test
>>>>for equal. When the same thing can be in
>>>>multiple places, unequal doesn't tell me
>>>>anything, which is annoying, especially when
>>>>tools think unequal to the expected value
>>>>means unusable. And when the same place can
>>>>hold different things, equal doesn't tell me
>>>>anything, which defeats the purpose.
>>>>
>>
>>Ken says:
>>
>>>What you are saying is it doesn't serve the
>>>purpose you have in mind, not that it doesn't
>>>serve other purposes quite well. One could say
>>>the success of the Web shows a real value.
>>>
>>
>>Whoa! I fully agree that URLs locate lots of
>>useful and functionally different things, just
>>as postal addresses do. But if today it's a
>>bank and tomorrow it's a laundry or a residence
>>or a casino, what "resource" is being
>>"identified"?
>>
>>What I said was that if the content to which a
>>URI refers changes radically from day to day,
>>the URI doesn't identify "an information
>>resource" in any useful sense. And thus the
>>idea that the URI identifies something
>>different from a location is false. If the
>>purpose of a URI is to denote content,
>>function, behavior, as distinct from location,
>>some one of those has to be consistent over
>>time. A bulletin board and a pulpit are just
>>locations.
>>
>>>>(I wonder how many XML tools would break if
>>>>the namespace URL for XML Schema pointed to a
>>>>local copy of the specification... Is the W3C
>>>>URI THE name or A name for the XML Schema
>>>>specification?)
>>>>
>>>This is where provenance comes in. It is THE
>>>URI if you believe W3C to be the authoritative
>>>source.
>>>
>>
>>This confuses two ideas:
>>1. The location of the document
>>2. The identity of the document as the one
>>issued by the authoritative source.
>>
>>Example: The authoritative source for the
>>Oxford Dictionary of English is presumably in
>>Oxford, England, but I can find the document at
>>my public library.
>>
>>All of the copies of the ODE have the same
>>designation, but you can find copies in lots of
>>places. So if I point you to a place where you
>>can find it, that has nothing to do with the
>>authoritative source.
>>
>>But my example was wrong. The xmlns reference
>>is to the "namespace URI", which is the
>>required *identifier* for the specification.
>>The tool is free to get a copy from anywhere it
>>likes. So if I put another URL there, it may be
>>a location of a copy of the specification, but
>>it is NOT the *identifier*, and the tool should
>>fail. It is exactly as if I referred to the
>>"Peoria Public Library's dictionary" instead of
>>the ODE.
>>
>>>>The webhead idea is that you will always go
>>>>to the URL, fetch the resource, and use it.
>>>>The idea that a tool has been pre-programmed
>>>>to support that *content*, and, in conducting
>>>>a web-based transaction, this might require
>>>>the tool to fetch and compare two 10MB files
>>>>to determine whether they are *versions of*
>>>>the same specification, is beyond their
>>>>hobbyist view of the Internet.
>>>>
>>>So what metadata do you need in place to
>>>support your use? How do you want to create
>>>and maintain that metadata? Will you make it
>>>available for others to use?
>>>
>>
>>Ah, now we are talking about what "responsible
>>management" of referenceable resources might
>>be. This is the kind of discipline that the
>>WebDAV folks have worked on, and there is a
>>"widely accepted" scheme for life cycle
>>management of documents. The trouble is that it
>>is widely accepted among the various
>>organizations involved in making document and
>>metadata standards, but those folks operate and
>>influence less than 1% of websites. It does
>>mean that publishers, and standards
>>organizations, and library websites will
>>probably use it.
>>
>>>Everything is a resource to someone, as it
>>>should be. What we want to be able to do is
>>>differentiate resources so we use the one(s)
>>>most suitable for our needs.
>>>
>>
>>Exactly. But unless there are common
>>conventions for that differentiation, all we
>>have is a bunch of disorganized resources
>>labeled according to hundreds or thousands of
>>incompatible schemes, most of which are not
>>very good or very useful. Google has built a
>>successful enterprise on the failure of the
>>Web, and its principal resources, to address
>>that problem. And there are many who believe
>>that that also is as it should be.
>>
>>IMO, the problem is that Internet is still the
>>big city of the Middle Ages. We know how to
>>build all kinds of buildings and we have a lot
>>of demand for them and a lot of construction of
>>various kinds and qualities going on. But no
>>one is responsible for much of it, we have no
>>civil engineering discipline, we have no land
>>use planning, we have random patchworks of
>>streets, we are carrying the water on foot in
>>buckets from the most convenient well, we have
>>no police force and no fire brigade, we have
>>sewage problems, crime problems and frequent
>>plagues. Some communities thrive and some die
>>out, and we don't really understand why. And
>>yet people keep coming here, because there is
>>education, and jobs, and entertainment, and
>>money to be made. Ultimately, technology
>>enabled us to get control of it, and fires and
>>plagues forced us to. But it took 7 centuries.
>>I hope the Internet experience is shorter.
>>
>>-Ed
>>
>>--
>>Edward J. Barkmeyer Email: <mailto:edbark@xxxxxxxx>edbark@xxxxxxxx
>>National Institute of Standards & Technology
>>Manufacturing Systems Integration Division
>>100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
>>Gaithersburg, MD 20899-8263 FAX: +1 301-975-4694
>>
>>"The opinions expressed above do not reflect consensus of NIST,
>>and have not been reviewed by any Government authority."
>>
>
>------------------------------------------------------------------------------------------
>Ken Laskey
>MITRE Corporation, M/S H305 phone: 703-983-7934
>7515 Colshire Drive fax: 703-983-1379
>McLean VA 22102-7508
>
>
>
>
>
>
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