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Subject: RE: The use-mention distinction

Title: Re: [xdi] on global cross references and the link contract use case

OK, Drummond, my hat is off to you.  You sure have pulled some interesting references to back up this proposal.  I had never heard of the use_mention_distinction before.  How many English speaking humans do you think have? 


Random thoughts ….


This still does not tell me why XDI or XRI needs this capability.  I am still looking for the requirement.   All of these arguments seem to be justifying the proposed solution. 


Using the English language as a model is scary in its complexity.  Nuances such as these often get us in trouble.


Rather than precision this seems to bring ambiguity especially since there are no proposed policies on how they are used.  If looking for precision it would seem looking at mathematical syntax rather than linguistic syntax may be a better guide.


Seems to me that if there “really” needs to be a distinction between “use” and “mention” it should be done in the XRD.  (Note:  first set of quotes intended to be scary quotes while the second set intended to be mentions or is it uses … I don’t know … I confuse myself)


Is the requirement to enable use_mention or the previously mentioned need of  scary_quotes?  I am not certain but I think these are different concepts.    I wonder, should XRI and XDI support both use_mention and scary_quotes.  How about italics and object language and formal language and kleene stars and the million other language constructs that can be found in Wikipedia.   I am not a linguist and do not claim to understand these concepts.


I still have to ask why this is needed.  The only argument that makes any sense to my simple mind is cosmetics when stringing large XRIs together in statements such as $IS$A or $HAS$A or +international+employment$contract$sig$d. 




From: Drummond Reed [mailto:drummond.reed@cordance.net]
Sent: Wednesday, November 26, 2008 7:55 PM
To: Chasen, Les; giovanni.bartolomeo@uniroma2.it; xdi@lists.oasis-open.org
Subject: The use-mention distinction


> Les wrote:


> What is the english difference between these two statements:
> +international+employment$contract$sig$d
> And

> +international*(+employment)*($contract)*($sig)*($d)


With the caveat that English equivalents of XDI RDF statements are only an analogy, here’s the translation (assuming $sig = “signature” and $d = “date”):


            XRI                   +international+employment$contract$sig$d

            English             international employment contract signature date


            XRI                   +international*(+employment)*($contract)*($sig)*($d)

            English             international “employment” “contract” “signature” “date”


The key point being that an XRI cross-reference expresses roughly the same concept as the English concept of the Use-Mention Distinction:




As explained in the introduction to that Wikipedia page:

The use–mention distinction (sometimes referred to as the words-as-words distinction) is the distinction between using a word (or phrase) and mentioning it. For example, the following two sentences illustrate use and mention of the word cheese:

  • Cheese is derived from milk.
  • Cheese is derived from a word in Old English.

The first sentence is a statement about the substance cheese. It uses the word cheese to describe its referent. The second is a statement about the word cheese. It mentions the word without using it.

In written language, mentioned words or phrases often appear between quotation marks ("Chicago" contains three vowels) or in italics (When I refer to honey, I mean the sweet stuff that bees make), and some authorities insist that mentioned words or phrases must always be made visually distinct in this manner. Used words or phrases (much more common than mentioned ones) do not bear any typographic distinction.


The irony behind the http://wiki.oasis-open.org/xri/XriThree/GcsDelimiter proposal is highlighted by the last sentence above where it says, “Used words or phrases (_much more common_ than mentioned ones)…” (emphasis added).


Our history in XRI is that first we recognized, way back in the prehistory days (2000) that XRI syntax needed a way to encapsulated (and thereby reuse) identifiers from other contexts (most specifically, absolute URIs, but also relative URIs and other string-based identifiers). We invented the parenthetical cross-reference syntax to do that. Since that was the ONLY mechanism we had for reusing identifiers, we also used it to reuse global XRIs in the context of other global XRIs. That meant that the ONLY way to refer to =drummond in the context of @cordance was to express it as either:





Therefore, to use the terminology of the Wikipedia articile, we semantically interpreted such a cross-reference as a _use_ of =drummond and not a _mention_ of =drummond.


However as we began to run into issues with restricting global XRI reuse to cross-reference syntax, the idea first arose that GCS characters could function as delimiters just like LCS characters (* and !). That meant we could express one global XRI directly in the context of another global XRI, e.g.:




This syntax was directly parallel to English, where the direct _use_ of one English word in the context of another English word requires no special syntax other than creating an ordered set of the words. This is expressed in the last sentence of the Wikipedia quote above:


Used words or phrases (much more common than mentioned ones) do not bear any typographic distinction.


From an XRI standpoint, suddenly everything snapped into place. The ordinary _use_ of one global XRI in the context of another XRI could be accomplished simply by creating an ordered set of the global XRIs, without any special syntax. This would align it directly with English. Then the special exception, i.e, the _mention_ of a global XRI without intending its normal use, would be represented by cross-reference syntax. That means in English:


            XRI                   @cordance=drummond

            English             Cordance Drummond


            XRI                   @cordance*(=drummond)

            English             Cordance “Drummond”


Following the use-mention distinction, the presumption would be that the =drummond in @cordance=drummond is the regular _use_ of =drummond, and therefore is a reference – in Cordance’s context – to the same entity referred to by =drummond in its own (global) context.


By contrast, the presumption would be that the =drummond in @cordance*(=drummond) is a _mention_ of =drummond, and therefore should NOT be interpreted as a reference to =drummond in ordinary _use_. (What it should be a reference to is up to @cordance as the authority for this subsegment.)


Personally, I think it is a combination of: A) the evolutionary history of XRI, and B) the subtlety of the use-mention distinction, that has take us so long to recognize and understand this issue, which is why I don’t blame Les for really pressing us to explain it.



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