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Subject: RE: [xdi] golden triangle (was Re: [xdi] $is is the universalinverse restriction)
Personally, I can see valid points in what Drummond, Markus, and now Giovanni have brought up in terms of the discussion of 'verb' vs. 'predicate' terminology. To sum up: .. 'Predicate' maintains backward compatibility with RDF better .. 'verb' is just a role .. Different opinions on which term is less confusing .. +name, +address, etc. do not look like verbs (in RDF these would likely be hasName, hasAddress, so they would be more verb like). .. Predicate accurately captures the functional aspect of a predicate/verb, but 'verb' doesn't seem to (my addition) I was trying to think of a term that addressed the above points. My first thought was 'action', but that seems to have several of the disadvantages of 'verb'. Then I hit on 'rel'. Each of these is a relation. 'rel'... .. Maintains backward compatibility with RDF and with Microformats. 'rel' has been used to explain RDF properties before in talks I've heard. .. 'rel' is not confusion I think, because of it's widely agreed on use within the HTML and Microformat communities .. +name, +address can be relations .. 'rel' I think captures the functional aspects in that rel clearly is a mapping .. 'rel' has the added bonus that it immediately conveys to me the graph idea of an arc, like it actually is in the graph. Not sure it will do the same to others .. '$rel' could be a superset of any XRI that can act as a 'rel', similar to $op for XDI operations What are everyone's further thoughts on 'verb', 'predicate', and 'rel'? If you've thought of a different term that you think might be a better fit then please put it out there for discussion as well. Kind regards, Bill Barnhill Booz Allen Hamilton - Rome, NY 315-330-7386 | william.barnhill.ctr@rl.af.mil | barnhill_william@bah.com ________________________________________ From: Giovanni Bartolomeo [giovanni.bartolomeo@uniroma2.it] Sent: Thursday, July 01, 2010 11:10 AM To: Drummond Reed Cc: Markus Sabadello; Joseph Boyle; OASIS - XDI TC Subject: [xdi] golden triangle (was Re: [xdi] $is is the universal inverse restriction) -1. I'd like "predicate" better, to maintain backward compatibility with RDF. BTW there are currently many issues with the "golden triangle" which are still very obscure (at least to me), including: $is$a as $word relating predicates with objects, $is and self referencing arc definition, $has$a definition as traversal of subject and predicate, +x/+y/+y and +x/+y/+x+y reintroduced, after we agreed that they were not needed, etc... Note that the current specs are totally based on the golden triangle: http://wiki.oasis-open.org/xdi/XdiOne/AddressingAndGraphModel This way it becomes very difficult - or sometimes even impossible - to think at XDI productions in terms of description logic. I think it would be better to rediscuss together the golden triangle, and probably revise the current specs page accordingly. Kind Regards, Giovanni Def. Quota "Drummond Reed" <drummond.reed@xdi.org>: > I don't think it's any more confusing than "predicate". "verb" is just a > role - the same XRI could be a subject, verb, and object (especially in an > XDI dictionary). > > But that's just one person's view. What do others think? > > =Drummond > > On Thu, Jun 10, 2010 at 2:28 AM, Markus Sabadello > <markus.sabadello@xdi.org>wrote: > >> Oh nooo I'll have to rename lots of stuff in XDI4j :) >> >> But seriously, isn't "verb" a bit confusing? +name, +address etc. don't >> look like verbs to me. >> >> Markus >> >> >> On Thu, Jun 10, 2010 at 10:49 AM, Drummond Reed >> <drummond.reed@xdi.org>wrote: >> >>> >>> >>> On Thu, Jun 10, 2010 at 12:51 AM, Joseph Boyle >>> <boyle.joseph@gmail.com>wrote: >>> >>>> >>>> On Jun 9, 2010, at 11:22 PM, Drummond Reed wrote: >>>> >>>> Joseph, first, my apologies for not replying earlier - I had another trip >>>> this week so my email is way behind. >>>> >>>> But we have another XDI TC telecon coming up tomorrow so I wanted to move >>>> discussion forward on the individual issues/questions about the example >>>> PDX document <http://wiki.oasis-open.org/xdi/PdxExample>. Here are my >>>> answers to your two questions about $is (copied from below to keep the >>>> thread clean): >>>> >>>> > 1) How do the two roles of $is form a single coherent concept? Right >>>> now the modifier role (as a passive voice marker modifying the following >>>> verb) and the standalone role (as the copulative verb) seem like distinct >>>> definitions to me. I realize this is analogous to the English verb "to be" >>>> that also serves in both these roles, but is there a philosophical / >>>> semantic / formal (take your pick) argument that this should logically be >>>> the case in XDI? >>>> >>>> You phrase that question very well. I have been thinking that in the >>>> spec, we need to define the semantics for each of the metagraph predicates >>>> for each of the following uses: >>>> >>>> 1) Standalone, e.g., $is >>>> >>>> 2) As a restriction on another predicate (i.e., preceeding it, e.g., >>>> $is+foo) >>>> >>>> 3) As an extension on another predicate (i.e., following it, e.g., >>>> +foo$is) >>>> >>>> >>>> Agreed, we must do this, and explain what the 3 usages for a given >>>> predicate have in common. (Are these the only 3, or are there even more >>>> possible uses?) >>>> >>> >>> I left out the other six options: Using the metagraph predicate as a 1) >>> standalone subject, 2) subject restriction, or 3) subject >>> extension, as well >>> as a 4) standalone object, 5) object restriction, 6) object extension. >>> >>> For many of those, the answer may be "undefined", but for some there are >>> very good answers. For example, $ as a standalone subject is the >>> XDI context >>> self-descriptor; and $has and $a are both used as the proposed subject >>> extensions to create link contracts as shown in the lower part of >>> the example >>> PDX document <http://wiki.oasis-open.org/xdi/PdxExample>. >>> >>>> >>>> I believe the definitions in each of these three roles must be logically >>>> consistent. For example, the definition of $is as a standalone >>>> predicate is >>>> synonymity between the subject XRI and object XRI (they both identify the >>>> same logical resource). This is as shown as a >>>> reflexive<http://en.wikipedia.org/wiki/Reflexive_relation>arc >>>> (self-referential -- originating and terminating in the same >>>> node) as >>>> illustrated in the golden >>>> triangle<http://www.oasis-open.org/committees/download.php/37568/xdi-golden-triangle.png>. >>>> >>>> >>>> >>>> The Golden Triangle diagram (I'm tempted to say the XDI Holy Trinity but >>>> should probably refrain) itself shows S and O as separate nodes though >>>> connected by arrows labeled $is. For the arc to be reflexive, S >>>> and O would >>>> have to merge and become a single node. Sorry if this sounds too >>>> literal. We >>>> do understand "$is" as making S and O equivalent - but this is something >>>> that we have to explain with text external to the diagram. Looking at the >>>> diagram alone naively, it is not obvious that the $is arcs merge >>>> S and O but >>>> that the other $a, $has arcs do not make S and P equivalent or P and O >>>> equivalent. >>>> >>> >>> I agree that the Golden Triangle diagram by itself does not make it clear >>> that the $is arc is reflexive. It needs some text with it to >>> explain that. I >>> have a separate intermediate diagram that explains the origins of >>> the Golden >>> Triangle diagram that makes that much clearer. I propose we use both in the >>> final spec. >>> >>>> >>>> The definition of $is as a restriction on another predicate is that it >>>> expresses the inverse of that predicate, e.g., the inverse of +b is $is+b >>>> (example: +a/+b/+c <=> +c/$is+b/+a). The logical connection with $is as a >>>> standalone verb is that $is, being reflexive arc, is being used >>>> to describe >>>> the verb it is restricting. As a reflexive arc, it is literally >>>> "reversing" >>>> the restricted verb. So $is+foo is the reverse (inverse) of +foo. >>>> >>>> This is one simplest yet most powerful examples of the utility of >>>> semantic (non-opaque) identifiers in XDI. >>>> >>>> >>>> > 2) One difference I notice between XDI terminology and linguistics >>>> terminology is that in the latter, "predicate" means verb together with >>>> object, not simply the verb. >>>> >>>> Ahhh, I didn't know that. As you know, I have no formal background in >>>> either linguistics or formal logic, so I am constantly learning >>>> nuances like >>>> this. What's the solution: are you suggesting we use the term >>>> "verb" instead >>>> of "predicate"? As in: XDI subject, XDI verb, XDI object? >>>> >>>> >>>> http://en.wikipedia.org/wiki/Predicate lists the differing meanings in >>>> grammar, logic, etc. >>>> >>>> XDI gets the term "predicate" from RDF which gets it from mathematical >>>> logic, where it specifically means a boolean-valued function. In this case >>>> both S and O would be considered arguments to the predicate, and >>>> the boolean >>>> result True from P(S,O) is expressed by the fact that the >>>> predicate is being >>>> stated / graphed at all while the boolean result False from >>>> P(S,O) would be >>>> expressed by not stating / graphing anything. This makes sense in >>>> one sense, >>>> but may not be the most intuitively obvious meaning, in addition to the >>>> conflict with the natural-language grammar that most people are familiar >>>> with. >>>> >>>> I would vote for "verb" not "predicate" in line with the trend towards >>>> using simple everyday natural-language-like terms in XDI, which >>>> has included >>>> using "$is", "$has", "$a" to replace more technical terms. This would be >>>> another break with RDF terminology, which may be good or bad depending on >>>> your viewpoint. I think some other knowledge representation systems have >>>> used "verb" in some way, but don't remember specifically. >>>> However, the only >>>> programming language I can think of offhand where "verb" is part of normal >>>> terminology is COBOL. :/ >>>> >>> >>> I agree with your logic, and with using "subject, verb, object" instead of >>> "subject, predicate, object". If anyone on the TC disagrees, please post, >>> else I will start using that in all the XDI-related text I'm writing. >>> >>> Thanks, >>> >>> =Drummond >>> >>> >>> >> > ---------------------------------------------------------------- Invito da parte dell'Ateneo: Il tuo futuro e quello della Ricerca Scientifica hanno bisogno del tuo aiuto. Dona il 5 x mille all'Universita' di Roma Tor Vergata codice fiscale: 80213750583 http://5x1000.uniroma2.it --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. 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