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Re: [ontolog-forum] {Disarmed} Re: OWL and lack of identifiers

To: "Cory Casanave" <cory-c@xxxxxxxxxxxxxxxxxxxxxxx>
Cc: "'[ontolog-forum] '" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Sun, 15 Apr 2007 18:40:14 -0500
Message-id: <p06230901c24867377969@[]>
>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)
>(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 
>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 
>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 
>>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 
>>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 
>>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 
>>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 
>>>>(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 
>>>This is where provenance comes in. It is THE 
>>>URI if you believe W3C to be the authoritative 
>>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.
>>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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>    (08)

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