- From: Adrian Walker <adriandwalker@gmail.com>
- Date: Fri, 15 Jan 2010 17:44:40 -0500
- To: Jiøí Procházka <ojirio@gmail.com>
- Cc: semantic-web@w3.org, Pat Hayes <phayes@ihmc.us>
- Message-ID: <1e89d6a41001151444y3fa084bew1645d49390c30467@mail.gmail.com>
Hi Jiřà -- You wrote: *Still information in RDF which is using ontology that is defined just by natural language (not descriptive - OWL) are worth something and up to a certain point can be processed by machines... * Actually, one can drop the "up to a certain point" qualifier, and say "*can*be processed by machines" . Here's how. We can keep RDF simple, and write the "ontology" in executable, open vocabulary English. Here's an example that you can view, run and change using a browser, www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent and here is a paper describing the underlying online system www.reengineeringllc.com/A_Wiki_for_Business_Rules_in_Open_Vocabulary_Executable_English.pdf The alert reader of the above paper will notice an interesting parallel with Pat Hayes' recent talk, in which the ungainly fragments in the middle 80% of the semantic web layer cake were replaced with a single elegant technology. -- Adrian Internet Business Logic A Wiki and SOA Endpoint for Executable Open Vocabulary English over SQL and RDF Online at www.reengineeringllc.com Shared use is free, and there are no advertisements Adrian Walker Reengineering -- Adrian 2010/1/15 Jiřà Procházka <ojirio@gmail.com> > On 01/15/2010 05:36 PM, Pat Hayes wrote: > > > > On Jan 15, 2010, at 1:58 AM, Jiřà Procházka wrote: > > > >> On 01/15/2010 08:06 AM, Pat Hayes wrote: > >>> > >>> On Jan 15, 2010, at 12:32 AM, Jiřà Procházka wrote: > >>> > >>>> On 01/15/2010 06:29 AM, Pat Hayes wrote: > >>>>> > >>>>> On Jan 14, 2010, at 10:50 PM, Jiřà Procházka wrote: > >>>>> > >>>>>> On 01/15/2010 04:17 AM, Pat Hayes wrote: > >>>>>>> > >>>>>>> <rant> > >>>>>>> This brings up a broader issue. Everyone agrees its good to keep > RDF > >>>>>>> simple. But keeping RDF simple by making it in effect into a > >>>>>>> general-purpose construction kit, and then expecting that as a > >>>>>>> matter of > >>>>>>> routine people will use the constructions, isn't really being > honest > >>>>>>> about 'simple'. OWL/RDF is a lot less simple than RDF itself > largely > >>>>>>> because its written in what we might more honestly call > >>>>>>> OWL-syntax-coded-in-lists-described-using-RDF, which IMO isn't > >>>>>>> really > >>>>>>> RDF any more. If we want to expect RDF to do this kind of thing, > >>>>>>> then it > >>>>>>> ought to have a whole datastructuring facility built in explicitly, > >>>>>>> perhaps along JSON lines, rather than prostituting the triple > >>>>>>> store to > >>>>>>> be a data structuring tool. > >>>>>>> </rant> > >>>>>> > >>>>>> Wasn't this the whole idea of RDF? Simple language for expressing > any > >>>>>> information? Doesn't it use triples, simple relations between two > >>>>>> objects, specifically for the reason that it is universal, and any > >>>>>> kind > >>>>>> of structure can be expressed by it? > >>>>> > >>>>> There are two notions of universal here, and we shouldn't get them > >>>>> confused. One is a universal programming language, which can be > >>>>> used to > >>>>> build arbitrary data structures and define operations over them. In > >>>>> other words, in fact, a programming language. The other sense is a > >>>>> universal *descriptive* language, which RDF is supposed to be , but > >>>>> isn't because it is too simple. (Thats why we need OWL, etc.; > >>>>> though RDF > >>>>> is closer than I used to think, see my ISWC talk.) > >>>>> > >>>>> My point was only that if RDF needs to *use* sequences (like, as data > >>>>> structures to encode OWL syntax, for example, or as a way of hacking > >>>>> N-ary relations using only binary links) then this is more like > >>>>> building > >>>>> data structures than describing anything, and maybe it would be > better > >>>>> to admit this up front and deal with it with a real datatstructuring > >>>>> notation. It wasn't the whole idea of RDF to have it be a kind of > >>>>> awkward version of simplified LISP. > >>>> > >>>> No, I am not mixing in programming languages, I am talking about > >>>> descriptive language, though I am not a logician, so could you please > >>>> explain what universal descriptive language needs to fulfill (or > >>>> provide > >>>> a link to such explanation)? I cannot imagine anything that cannot be > >>>> described by RDF+RDFS - you say we need OWL - but OWL is defined using > >>>> RDF+RDFS. > >>> > >>> No, its not! OWL is a different language from RDF, and its not defined > >>> in RDF. In fact, it couldn't be defined in RDF, since RDF is not > >>> expressive enough. Both RDFS and OWL/RDF are semantic extensions of > RDF, > >>> but that means that they need 'extra' semantics in addition to that > >>> provided by RDF. In the case of OWL/RDF, it wasn't at all easy to > >>> specify this stuff and keep it consistent with the RDF meanings. > >> > >> Now things clears up! > >> I think we differ in that, that I consider every RDF vocabulary a > >> semantic extension. You can describe things using descriptive languages > >> like OWL or RDFS, but also using natural language. > > > > True, but what then is the purpose of RDF? Why don't we just use English > > as the semantic web formalism? This seems to me to be the reductio ad > > absurdum of your point of view. The idea of the SWeb is that semantic > > information written in RDF can be processed by machines. And the > > technology of RDFS, OWL, SPARQL etc. depends entirely upon genuine > > semantic extensions (as defined in the spec itself) , not just a > > let-it-all-hang-out idea that anything comment written anywhere can > > count as an RDF-defined meaning postulate. > > Still information in RDF which is using ontology that is defined just by > natural language (not descriptive - OWL) are worth something and up to a > certain point can be processed by machines - an engineer has to teach > his application the ontology. > > Look at FOAF for example... Undoubtedly there is demand for such > lightweight semantics. If it was to be defined by some descriptive > language... to be frank, I can't imagine that - it would probably be > some upper ontology stuff which is subject of many disagreements. That > is why we shouldn't embrace one specific descriptive language as main > RDF formalism, we should be able to choose it, therefore defining the > level our ontologies can be reasoned about by machines. Saying something > like "DL should be good enough for everyone" might be a mistake... > > As I understand it, you expect to teach your machine RDF, and be able to > "understand" whole semantic web. My view is I have to continuously teach > it new formalism which are starting to get used on the web (unless they > are defined by some formalism it already understands). > > I'm all for having a widely used and W3C blessed ontology for defining > ontologies using set theory and formal logic, on top of RDF, but not as > a part of it. I guess it's mainly a question of proper modular design > and low barrier of entry, since I don't know of any competing logic > theories to be honest, but I expect there are some or will be in future. > > Best, > Jiri > > PS: Others: Sorry for confusion, 3 mails accidentally went off list, > they are quoted here of course. > > >> In any case your > >> description is just a imperfect surrogate of your view of the described > >> things (depending how deep is your understanding and how good is your > >> skill with the descriptive/natural language) which is a surrogate of the > >> things themselves (depends what philosophy you subscribe to). > >> If we want RDF to be universal information interchange language, we > >> shouldn't bless one way of reasoning about things (DL) or enforce usage > >> of some top-level ontology (which is essentially the same thing), and > >> expect data to be semantic mess like minds of all people put together... > >> > >>>> Anyway you probably meant the universal descriptive language has to be > >>>> able to describe anything using only it's own terms, be self-hosted > >>>> (bootstrapped), not aided by natural language like with RDFS. > >>> > >>> RDFS is defined by the RDFS semantic conditions, not by natural > language > >> > >> And how are these semantic conditions defined? > > > > Using *mathematics*. And this is not a joke: although the math may be > > written in English, the only aspects of English meaning that it relies > > upon are those that define the meanings of terms in set theory and > > formal logic. > > > >> > >> Best, > >> Jiri > >> > >> PS: You took the discussion off list, dunno if it's intentional > > > > No, it wasnt intentional. But whatever :-) > > > >> , any way > >> is good with me. Maybe will write a blog post someday about what I learn > >> from you. > >> > >> > >>>> I don't see why it needs to be that way, in fact I see that as its > >>>> strength - we can use it to describe things with various levels of > >>>> detail. For example I can define simply: > >>>> > >>>> <NaturalNumbers> a rdfs:Class ; > >>>> rdfs:comment "A class of natural numbers - integers which are greater > >>>> than zero" . > >>> > >>> But you still need some way to actually write the numbers down, ie some > >>> numerical convention. There are several of them, so you need to say > >>> which one you are using. Now you have datatyped literals. > >>> > >>>> > >>>> Or I could use OWL and express formally it's relation to integers, > >>>> but I > >>>> don't need to. > >>>> > >>>>>> Why should we give preferential > >>>>>> treatment to relations describing structure than those describing > >>>>>> time, > >>>>>> measures, events, organizations, people, pizzas...? > >>>>> > >>>>> Because they aren't *descriptions* of structure, they are structures > >>>>> being used to describe other things. Just like triples are. > >>>> > >>>> I believe triples were chosen because they are the simplest of the > >>>> structures, yet can describe any other. > >>> > >>> They are simplest and extremely useful, yes. But using them to > >>> *describe* others, which are then also themselves used to describe > other > >>> things, gets the syntax/semantic levels all mixed up. > >>> > >>>> > >>>> Do you intend to define all structures possible which can be used to > >>>> describe other things? > >>>> > >>>>>> This is what I always thought what RDF was supposed to be and things > >>>>>> like containers, blank nodes, literal data types, language tags > >>>>>> got in > >>>>>> because of pragmatical reasons, mainly to give users some kind of > >>>>>> direction, examples how to get started. > >>>>> > >>>>> Well, not really. All of these things are needed in order to describe > >>>>> things that people wanted to describe, and couldn't be described any > >>>>> other way. If you don't have literals, how are you going to use > >>>>> numbers > >>>>> in a description? Without language tags, how are you going to say > that > >>>>> something is written in French? Well, OK, maybe containers... > >>>> > >>>> <data:text/plain;charset=utf-8,Je%20ne%20comprends%20pas.> ex:language > >>>> lang:French . > >>> > >>> Well, OK, but you essentially have the lang tags here as language > >>> 'classes'. Whats the advantage? If these are part of the language, then > >>> they are just more longwinded tags. If they aren't, then what "knows" > >>> that lang:French means French? (RDF doesn't know this, right?) > >>> > >>> I think we did try out a design like this with language properties. But > >>> you have to say what it means when the language information is missing. > >>> Tags in literals make it compulsory, which is good for some purposes. > >>> > >>>> > >>>> I don't advocate using data URI scheme instead of literals, but it > >>>> should be possible. > >>>> Maybe you are right about the blank nodes though, I am not sure if > this > >>>> would work (meaning the URI is irrelevant): > >>>> > >>>> <j48fd8dj3> rdf:type ex:UnnamedNode . > >>> > >>> No, that confuses use and mention. The thing denoted isn't a blank > node. > >>> > >>>> > >>>>>> Reality that even such thing as RDFS was made separate of the RDF > >>>>>> itself > >>>>>> support my view (even though I suspect one of reasons if that > >>>>>> separation > >>>>>> was the process of it's development). > >>>>> > >>>>> Yes, most the latter. I would have preferred to have one namespace, > >>>>> but > >>>>> this was set in stone very early on. > >>>>> > >>>>>> > >>>>>> On the other hand I am not against creating community developed > >>>>>> framework for making common uses of Semantic Web technologies > easier, > >>>>>> defining useful structures and design patterns... but build that *on > >>>>>> top* of RDF as separate framework. > >>>>>> > >>>>>> I would like RDF to be as lightweight (low level) as possible - if I > >>>>>> were to make mine RDF, there would be no containers, bnodes, literal > >>>>>> data types, language tags, maybe even no literals - using data URI > >>>>>> scheme. Anyway I value compatibility and adoption more than > >>>>>> sticking to > >>>>>> my view of the world so I use RDF as it is. > >>>>>> > >>>>>> Other alternative would be to have the low level core, build > >>>>>> modules on > >>>>>> top of it, for example like some programming languages do (Python, > >>>>>> Java...) and call the whole thing RDF - I guess that is what would > >>>>>> make > >>>>>> most people happy. > >>>>> > >>>>> But this whole idea of 'building modules on top' is a programming > >>>>> idea, > >>>>> not a description language idea. It muddles up the notion of a > >>>>> description. Which 'level' defines the semantics you should be > >>>>> using in > >>>>> a query? There's no way to know. > >>>> > >>>> You can use any level, because all levels are defined by levels under > >>>> them, lowest of them being RDF core. > >>> > >>> What do you mean by one level being "defined" by another, if these are > >>> all descriptive languages? Do you imagine RDF core ontologies being > used > >>> to describe higher-level meanings? Because that (provably) will not > >>> work: RDF isn't expressive enough. And if it were expressive enough, > >>> then we wouldn't need the higher levels, except maybe as syntactic > >>> sugar. > >>> > >>> Pat > >>> > >>>> > >>>> Best, > >>>> Jiri > >>>> > >>>> PS: Actually there is one thing which would aid bootstrapped nature of > >>>> RDF: > >>>> > >>>> ex:contains rdf:type rdf:Property ; > >>>> rdfs:comment "property for stating that a reified triple is part of > >>>> graph" ; > >>>> rdfs:range rdf:Statement . > >>>> > >>>>> Pat > >>>>> > >>>>>> > >>>>>> Best, > >>>>>> Jiri Prochazka > >>>>>> > >>>>>>> > >>>>>>> Pat > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>>> > >>>>>>>> Rgds, > >>>>>>>> > >>>>>>>> -Geoff > >>>>>>>> > >>>>>>>> > >>>>>>>> > >>>>>>>> > >>>>>>>> > >>>>>>> > >>>>>>> ------------------------------------------------------------ > >>>>>>> IHMC (850)434 8903 or (650)494 > >>>>>>> 3973 > >>>>>>> 40 South Alcaniz St. (850)202 4416 office > >>>>>>> Pensacola (850)202 4440 fax > >>>>>>> FL 32502 (850)291 0667 mobile > >>>>>>> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>> > >>>>> > >>>>> ------------------------------------------------------------ > >>>>> IHMC (850)434 8903 or (650)494 > >>>>> 3973 > >>>>> 40 South Alcaniz St. (850)202 4416 office > >>>>> Pensacola (850)202 4440 fax > >>>>> FL 32502 (850)291 0667 mobile > >>>>> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes > >>>>> > >>>>> > >>>>> > >>>>> > >>>>> > >>>> > >>> > >>> ------------------------------------------------------------ > >>> IHMC (850)434 8903 or (650)494 3973 > >>> 40 South Alcaniz St. (850)202 4416 office > >>> Pensacola (850)202 4440 fax > >>> FL 32502 (850)291 0667 mobile > >>> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes > >>> > >>> > >>> > >>> > >>> > >> > > > > ------------------------------------------------------------ > > IHMC (850)434 8903 or (650)494 3973 > > 40 South Alcaniz St. (850)202 4416 office > > Pensacola (850)202 4440 fax > > FL 32502 (850)291 0667 mobile > > phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes > > > > > > > > > > > >
Received on Friday, 15 January 2010 22:45:15 UTC