Re: RDF Investigations
On Mon, Jun 24, 2013 at 11:02 PM, Pat Hayes pha...@ihmc.us wrote: ...snip Well, its a formal, artificial, language, and it comes with a semantics as part of its definition. Just like many other logics in many logic textbooks, many programming languages, etc.. So yes, I guess it does privilege that semantics, since that semantics is part of it (by definition). Hi Pat, Out of mercy for the other folks on the list, I think the thing to do is address the points you've raise one way or another in blog posts. I somehow doubt there's very much interest in watching the two of us go back and forth about the meaning of abstract. Once I get some text up with sufficient detail, if it seems appropriate I'll post a note and you can have another go at me then. Thanks, Gregg
Re: RDF Investigations
On Jun 25, 2013, at 1:36 PM, Gregg Reynolds wrote: On Mon, Jun 24, 2013 at 11:02 PM, Pat Hayes pha...@ihmc.us wrote: ...snip Well, its a formal, artificial, language, and it comes with a semantics as part of its definition. Just like many other logics in many logic textbooks, many programming languages, etc.. So yes, I guess it does privilege that semantics, since that semantics is part of it (by definition). Hi Pat, Out of mercy for the other folks on the list, I think the thing to do is address the points you've raise one way or another in blog posts. I somehow doubt there's very much interest in watching the two of us go back and forth about the meaning of abstract. Quite right. I have no intention of going back and forth with you on this topic any further. Pat Once I get some text up with sufficient detail, if it seems appropriate I'll post a note and you can have another go at me then. Thanks, Gregg 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
Re: RDF Investigations
On Jun 23, 2013, at 11:49 AM, Gregg Reynolds wrote: Hi folks, A couple of years ago I got the idea of finding alternatives to the official definition of RDF, especially the semantics. I've always found the official docs less than crystal clear, and have always harbored the suspicion that the model-theoretic definition of RDF semantics offered in http://www.w3.org/TR/rdf-mt/ was unnecessary, or at least unnecessarily complicated. Needless to say that is my own personal aesthetic judgment, but it did motivate my little project. I guess the past two years have not been completely wasted on me; what was a somewhat vague intuition back then seems to have matured into a pretty clear idea of how RDF ought to be conceptualized and formally defined. Clear to me, anyway; whether it is to others, and whether it is correct or not is a whole 'nother matter. Since pursuing this idea will involve a lot of writing I won't pursue it here; instead I've described the the basic ideas in a blog post at http://blog.mobileink.com/. Hmm. You say some things in there that seem to be just plain wrong. 1. [The RDF semantics] restricts interpretation to a single semantic domain. I am not sure how you can possibly read the semantics in this way, but the whole point of model theory is to permit many - usually, infinitely many - interpretations, over arbitrary domains. The only domain restriction in RDF (as in most model theories) is that the domain be non-empty and that it contain basic literal values such as character strings. 2. The so-called abstract syntax described in RDF Concepts and Abstract Syntax serves as the formula calculus, but it is incomplete. It specifies that a triple (statement) contains three terms (nodes), and that an RDF graph is a set of triples. But these are not rules of a calculus; they do not tell us how to construct statements in a formal language. First, the whole point of defining an 'abstract' syntax is to allow for a variety of concrete (lexical) syntaxes, so if you prefer to work at a concrete level, just choose one of those, eg RDF/XML or N-Triples. But more to the point, the abstract graph syntax *is* a formal language with a perfectly well-defined syntax. It is not a character-string syntax, but it is a syntax, with exact syntactic rules. A very simple syntax, but that simplicity was a deliberate part of the design. 3. ... semantic entailment (not to be confused with logical entailment)... Can you elicidate what you see as this distinction that is not to be confused? The textbook account of a formal logic distinguishes entailment, a purely semantic notion, often symbolized by the sign |=, from deducibility (via formal inference rules and axioms, typically), often symbolized by |-, and completeness is the property of these two coinciding. I do not know of any notion of logical *entailment* other than the semantic |= notion. Deducibility is not entailment. 4. The business of model theory is to build a bridge between formal calculi and (informal) semantic domains. You don't need a formal representation of the semantic domain... Model theory *is* the result of formalizing the semantic domain. That was the new idea in Tarski's original publication which founded the subject in the 1940s. HIs title, you might recall, was A theory of truth for formalized languages. 5. ...model theory, ... makes automated proof a legitimate idea. Proof theory makes automated proof a legitimate idea. Model theory establishes completeness of the formal proof methods. and I guess I won't bother to go on with this list. Your main point, however, seems to be that one could formalize RDF as an uninterpreted calculus and then go and look for alternative ways to interpret it, and maybe find some new ones. I am sure that this program would succeed, in the sense that you would indeed find alternative semantics. But let me ask the larger question: what exactly is the point of this enterprise? Since the only point of inventing RDF in the first place was to provide for a basic degree of interoperability at a semantic level, what purpose could there be in ignoring this aspect of RDF? Considered as a pure, uninterpreted formal calculus, RDF is hardly there at all, it is so minimal. As you point out, it does not come with any proof rules or indeed even with any notion of proof already defined for it, and if you don't think the graph syntax is adequate, then it doesn't even come with a syntax. So it is hardly there at all: no wonder you could, if you were so inclined, make it into just about anything at all, if you ignore the normative semantics. If you want to have fun with formalisms, why not choose something with a bit more bite to it, such as an uninterpreted lambda-calculus, say? Or Javascript? The allusion to Wittgenstein, that great philosophical therapist, is entirely intentional. You (or at least I) find out a lot of things when you
Re: RDF Investigations
On Sun, Jun 23, 2013 at 12:30 PM, Adrian Walker adriandwal...@gmail.com wrote: Hi Gregg, Interesting. You may like the example www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent For the non-aggregation parts of the example, the formal semantics in effect are described in Backchain Iteration: Towards a Practical Inference Method that is Simple Enough to be Proved Terminating, Sound and Complete. Journal of Automated Reasoning, 11:1-22 Thank you, I'll take a look. Gregg
Re: RDF Investigations
On 6/24/13 10:32 AM, Pat Hayes wrote: If you can give up on all this, what do you take yourself to be referring to when you say RDF ? You have just dismissed virtually every defining characteristic of RDF as either wrong or inessential. So what is left? Pat I am going to create a poll aimed as getting a feel for what folks perceive as the defining characteristics of RDF. In recent times, I've come to believe those characteristics aren't so clear anymore. Here's a draft of the questions for the poll: 1. Don't know 2. Don't care 3. Linked Data Creation 4. Interpretable Linked Data Creation 5. W3C standard. To you and anyone else that might be interested, are there any other questions I should add to the list above? -- Regards, Kingsley Idehen Founder CEO OpenLink Software Company Web: http://www.openlinksw.com Personal Weblog: http://www.openlinksw.com/blog/~kidehen Twitter/Identi.ca handle: @kidehen Google+ Profile: https://plus.google.com/112399767740508618350/about LinkedIn Profile: http://www.linkedin.com/in/kidehen smime.p7s Description: S/MIME Cryptographic Signature
Re: RDF Investigations
On Mon, Jun 24, 2013 at 9:32 AM, Pat Hayes pha...@ihmc.us wrote: Hi, and thanks for the comments. FYI I have some draft articles in the can that will add clarity and detail, I hope. In the meantime ... On Jun 23, 2013, at 11:49 AM, Gregg Reynolds wrote: Hi folks, A couple of years ago I got the idea of finding alternatives to the official definition of RDF, especially the semantics. I've always found the official docs less than crystal clear, and have always harbored the suspicion that the model-theoretic definition of RDF semantics offered in http://www.w3.org/TR/rdf-mt/ was unnecessary, or at least unnecessarily complicated. Needless to say that is my own personal aesthetic judgment, but it did motivate my little project. I guess the past two years have not been completely wasted on me; what was a somewhat vague intuition back then seems to have matured into a pretty clear idea of how RDF ought to be conceptualized and formally defined. Clear to me, anyway; whether it is to others, and whether it is correct or not is a whole 'nother matter. Since pursuing this idea will involve a lot of writing I won't pursue it here; instead I've described the the basic ideas in a blog post at http://blog.mobileink.com/. Hmm. You say some things in there that seem to be just plain wrong. 1. [The RDF semantics] restricts interpretation to a single semantic domain. I am not sure how you can possibly read the semantics in this way, but the whole point of model theory is to permit many - usually, infinitely many - interpretations, over arbitrary domains. The only domain restriction in RDF (as in most model theories) is that the domain be non-empty and that it contain basic literal values such as character strings. Point taken. My statement was incorrect and needs to be changed; the point I was trying to get at is that RDF-MT seems to privilege the domain it defines - the set IR of Resources, etc. The basic semantic constraints are stated in terms of this domain, which implicitly restricts semantic domains to those that have, for example, a set of binary relations for the properties. But this is not necessary; you can define models that do not contain such relations. An obvious example is a set of objects N and the set of their triples NxNxN. (I'll describe this in more detail in a later blog article). 2. The so-called abstract syntax described in RDF Concepts and Abstract Syntax serves as the formula calculus, but it is incomplete. It specifies that a triple (statement) contains three terms (nodes), and that an RDF graph is a set of triples. But these are not rules of a calculus; they do not tell us how to construct statements in a formal language. First, the whole point of defining an 'abstract' syntax is to allow for a variety of concrete (lexical) syntaxes, so if you prefer to work at a concrete level, just choose one of those, eg RDF/XML or N-Triples. It just dawned on me that when people talk about the abstract syntax of RDF in this manner what they often mean is abstract description of possible syntax (or set of syntaxes). Is that a fair description of what you have in mind? I can't see any other way to read it, since by definition what is abstract cannot be written down, and if you cannot write it down you may be able to think about it but you cannot use it to communicate. You can publish a document that describes a class of syntaxes abstractly, but you cannot publish and abstract syntax. I suppose one could describe an abstract syntax by referring only to syntactic positions and symbol classes; e.g. for Lisp something like the first symbol must be an opening delimiter, the second a function symbol, and so forth. But this would be useless for model theory, which needs not only symbols but tokens. Actually SGML did something like this; it's the only language I know of that describes something approximating an abstract syntax. But its abstract syntax is in fact concrete; it uses symbols like DELIM (made that up, don't recall the exact expression) for concrete symbol classes. But that makes for a meta-syntax, not an abstract syntax. There's nothing abstract about it; it's a concrete syntax that describes a class of other concrete syntaxes. One can think of it as *expressing a generalization or abstraction, but that's a lot different than saying it *is* abstract. A meta-syntax of this character is what RDF lacks. But more to the point, the abstract graph syntax *is* a formal language with a perfectly well-defined syntax. It is not a character-string syntax, but it is a syntax, with exact syntactic rules. A very simple syntax, but that simplicity was a deliberate part of the design. Can you point me to the rule that says how to write down a triple so that I can specify an interpretation for it? Here's an easy example off the top of my head of what I would count as a meta-syntax for (part of) simple RDF: define A, B, C, ... as
Re: RDF Investigations
On Mon, Jun 24, 2013 at 11:37 AM, Kingsley Idehen kide...@openlinksw.com wrote: On 6/24/13 10:32 AM, Pat Hayes wrote: If you can give up on all this, what do you take yourself to be referring to when you say RDF ? You have just dismissed virtually every defining characteristic of RDF as either wrong or inessential. So what is left? Pat I am going to create a poll aimed as getting a feel for what folks perceive as the defining characteristics of RDF. In recent times, I've come to believe those characteristics aren't so clear anymore. Kingsley, Kingsley, Kingsley, you old thread hijacker you. ;) Best of luck, but for the record, I don't have a dog in that fight. As far as I'm concerned people can use RDF to mean whatever they want it to mean, as long as the software works. -Gregg
Re: RDF Investigations
On 6/24/13 3:52 PM, Gregg Reynolds wrote: On Mon, Jun 24, 2013 at 11:37 AM, Kingsley Idehen kide...@openlinksw.com wrote: On 6/24/13 10:32 AM, Pat Hayes wrote: If you can give up on all this, what do you take yourself to be referring to when you say RDF ? You have just dismissed virtually every defining characteristic of RDF as either wrong or inessential. So what is left? Pat I am going to create a poll aimed as getting a feel for what folks perceive as the defining characteristics of RDF. In recent times, I've come to believe those characteristics aren't so clear anymore. Kingsley, Kingsley, Kingsley, you old thread hijacker you. ;) Best of luck, but for the record, I don't have a dog in that fight. As far as I'm concerned people can use RDF to mean whatever they want it to mean, as long as the software works. -Gregg Gregg, There is an issue here that for whatever reasons simply keeps on getting lost. The question is simple: what are the unique characteristics of RDF? What does RDF do uniquely? I actually believe RDF does have unique characteristics, but I am curious to see if mine are in alignment with views of others. I really don't want RDF to become something that's based on a leap of faith, we can do much better than that :-) -- Regards, Kingsley Idehen Founder CEO OpenLink Software Company Web: http://www.openlinksw.com Personal Weblog: http://www.openlinksw.com/blog/~kidehen Twitter/Identi.ca handle: @kidehen Google+ Profile: https://plus.google.com/112399767740508618350/about LinkedIn Profile: http://www.linkedin.com/in/kidehen smime.p7s Description: S/MIME Cryptographic Signature
Re: RDF Investigations
Kingsley, Let me give a shot to your question about the unique characteristics of RDF 1) RDF is based on the idea that the things being described have properties which have values, and that resources can be described by making statements 2) A Statement is modeled as a Triple (mathematically a model for a directed labeled edge). The set of triples makes a directed labeled graph. * The part that identifies the thing the statement is about (a web resource Web page document or a concept such as an Event, Place etc..) is called the subject. * The part that identifies the property or characteristic of the subject that the statement specifies (creator, creation-date, or language in these examples) is called the predicate. The predicate is the label of an directed arc from the subject node to the object node. * and the part that identifies the value of that property is called the object. 3) There are three kinds of nodes in RDF model (IRI, Blank Node and Literal (which can be plain or plain with a language or typed with a datatype). 4) RDF specification uses Web Identifiers based on IRI specification 5) RDF provides a mechanism to make statement about Statement: (reification) 6) RDF introduces concepts of Collection and Container (rdf:List (closed and ordered), rdf:Bag (open, unordered), rdf:Alt (alternative semantic), rdf:Seq (ordered)). 8) RDF is syntax-independent and could be serialized into different formats as long as these formats are isomorphic to RDF model. My list is not exhaustive, but I hope I captured the essence of the data model. Best regards Stephane On Mon, Jun 24, 2013 at 4:21 PM, Kingsley Idehen kide...@openlinksw.comwrote: On 6/24/13 3:52 PM, Gregg Reynolds wrote: On Mon, Jun 24, 2013 at 11:37 AM, Kingsley Idehen kide...@openlinksw.com wrote: On 6/24/13 10:32 AM, Pat Hayes wrote: If you can give up on all this, what do you take yourself to be referring to when you say RDF ? You have just dismissed virtually every defining characteristic of RDF as either wrong or inessential. So what is left? Pat I am going to create a poll aimed as getting a feel for what folks perceive as the defining characteristics of RDF. In recent times, I've come to believe those characteristics aren't so clear anymore. Kingsley, Kingsley, Kingsley, you old thread hijacker you. ;) Best of luck, but for the record, I don't have a dog in that fight. As far as I'm concerned people can use RDF to mean whatever they want it to mean, as long as the software works. -Gregg Gregg, There is an issue here that for whatever reasons simply keeps on getting lost. The question is simple: what are the unique characteristics of RDF? What does RDF do uniquely? I actually believe RDF does have unique characteristics, but I am curious to see if mine are in alignment with views of others. I really don't want RDF to become something that's based on a leap of faith, we can do much better than that :-) -- Regards, Kingsley Idehen Founder CEO OpenLink Software Company Web: http://www.openlinksw.com Personal Weblog: http://www.openlinksw.com/**blog/~kidehenhttp://www.openlinksw.com/blog/~kidehen Twitter/Identi.ca handle: @kidehen Google+ Profile: https://plus.google.com/**112399767740508618350/abouthttps://plus.google.com/112399767740508618350/about LinkedIn Profile: http://www.linkedin.com/in/**kidehenhttp://www.linkedin.com/in/kidehen
Re: RDF Investigations
On Jun 24, 2013, at 2:07 PM, Gregg Reynolds wrote: On Mon, Jun 24, 2013 at 9:32 AM, Pat Hayes pha...@ihmc.us wrote: Hi, and thanks for the comments. FYI I have some draft articles in the can that will add clarity and detail, I hope. In the meantime ... On Jun 23, 2013, at 11:49 AM, Gregg Reynolds wrote: Hi folks, A couple of years ago I got the idea of finding alternatives to the official definition of RDF, especially the semantics. I've always found the official docs less than crystal clear, and have always harbored the suspicion that the model-theoretic definition of RDF semantics offered in http://www.w3.org/TR/rdf-mt/ was unnecessary, or at least unnecessarily complicated. Needless to say that is my own personal aesthetic judgment, but it did motivate my little project. I guess the past two years have not been completely wasted on me; what was a somewhat vague intuition back then seems to have matured into a pretty clear idea of how RDF ought to be conceptualized and formally defined. Clear to me, anyway; whether it is to others, and whether it is correct or not is a whole 'nother matter. Since pursuing this idea will involve a lot of writing I won't pursue it here; instead I've described the the basic ideas in a blog post at http://blog.mobileink.com/. Hmm. You say some things in there that seem to be just plain wrong. 1. [The RDF semantics] restricts interpretation to a single semantic domain. I am not sure how you can possibly read the semantics in this way, but the whole point of model theory is to permit many - usually, infinitely many - interpretations, over arbitrary domains. The only domain restriction in RDF (as in most model theories) is that the domain be non-empty and that it contain basic literal values such as character strings. Point taken. My statement was incorrect and needs to be changed; the point I was trying to get at is that RDF-MT seems to privilege the domain it defines - the set IR of Resources, etc. Well, its a formal, artificial, language, and it comes with a semantics as part of its definition. Just like many other logics in many logic textbooks, many programming languages, etc.. So yes, I guess it does privilege that semantics, since that semantics is part of it (by definition). The basic semantic constraints are stated in terms of this domain, which implicitly restricts semantic domains to those that have, for example, a set of binary relations for the properties. But this is not necessary; you can define models that do not contain such relations. You *can* (re)define RDF graphs to be a musical notation, or a way of drawing simple cartoons. So what? An obvious example is a set of objects N and the set of their triples NxNxN. (I'll describe this in more detail in a later blog article). Have you checked out the mapping from RDF to FOL mentioned in passing in the 2004 Semantics document? It maps an RDF triple S P O to the atomic sentence triple(S, P, O). You might find it congenial. 2. The so-called abstract syntax described in RDF Concepts and Abstract Syntax serves as the formula calculus, but it is incomplete. It specifies that a triple (statement) contains three terms (nodes), and that an RDF graph is a set of triples. But these are not rules of a calculus; they do not tell us how to construct statements in a formal language. First, the whole point of defining an 'abstract' syntax is to allow for a variety of concrete (lexical) syntaxes, so if you prefer to work at a concrete level, just choose one of those, eg RDF/XML or N-Triples. It just dawned on me that when people talk about the abstract syntax of RDF in this manner what they often mean is abstract description of possible syntax (or set of syntaxes). Is that a fair description of what you have in mind? That is one way to read it, but what I had in mind in using the term abstract syntax was the way it is used by John McCarthy (who coined the term originally), as syntax re-described as an algebra on terms and expressions. RDF uses graphs since its syntax is so extremely simple that it does not actually require any algebraic structure, but the basic idea is the same. I can't see any other way to read it, since by definition what is abstract cannot be written down, and if you cannot write it down you may be able to think about it but you cannot use it to communicate. It is a structure (the graph) which can be described and its properties given precisely, and it can be directly represented in computer memory as a datastructure. That is enough to make it a syntax as far as I am concerned. What it is not, is a grammar defined on character strings. Concrete RDF syntaxes like RDF/XML and NTriples can be described this way, of course (though for XML, better ways are available.) You can publish a document that describes a class of syntaxes abstractly, but you cannot publish and abstract
RDF Investigations
Hi folks, A couple of years ago I got the idea of finding alternatives to the official definition of RDF, especially the semantics. I've always found the official docs less than crystal clear, and have always harbored the suspicion that the model-theoretic definition of RDF semantics offered in http://www.w3.org/TR/rdf-mt/ was unnecessary, or at least unnecessarily complicated. Needless to say that is my own personal aesthetic judgment, but it did motivate my little project. I guess the past two years have not been completely wasted on me; what was a somewhat vague intuition back then seems to have matured into a pretty clear idea of how RDF ought to be conceptualized and formally defined. Clear to me, anyway; whether it is to others, and whether it is correct or not is a whole 'nother matter. Since pursuing this idea will involve a lot of writing I won't pursue it here; instead I've described the the basic ideas in a blog post at http://blog.mobileink.com/. The allusion to Wittgenstein, that great philosophical therapist, is entirely intentional. You (or at least I) find out a lot of things when you analyze a concept very closely; if my analysis is not mistaken, there are some fundamental problems in the land of RDF. For example, it is possible to show, among other things, that the concept of a graph is not essential to RDF; nor is the treatment of the Property node of a triple as an arrow or relation necessary; nor is the concrete semantics defined in the RDF Semantics document the only or even the best theory of RDF. (Maybe this is all obvious to the cognoscenti, but insistence that RDF just is a graph is very common.) On the positive side, thinking about RDF as a mathematical domain (or domains), independent of RDF as a language, leads to a pretty substantial improvement in clarity; and since it requires a certain amount of creativity it's just fun. The reason I'm posting this here is because I will need some help, especially from real mathematicians and logicians. A category theorist, for example. Not only to check my reasoning; my hope is that others interested in pursuing this line of thought might come up with yet other fresh ideas. Plus, I've had a lot of fun thinking along those lines, and since a lot of people on this list spend a lot of time thinking about RDF (among other things), I thought they might find it interesting and fun as well. The plan is to post a series of blog articles fleshing out the ideas in coming months, so if anybody would like to help or collaborate please let me know. Cheers, Gregg Reynolds
Re: RDF Investigations
Hi Gregg, Interesting. You may like the example www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent For the non-aggregation parts of the example, the formal semantics in effect are described in Backchain Iteration: Towards a Practical Inference Method that is Simple Enough to be Proved Terminating, Sound and Complete. Journal of Automated Reasoning, 11:1-22 Cheers, -- Adrian Internet Business Logic Open Apps for Open Data A Wiki and SOA Endpoint for Executable Open Vocabulary English Q/A Apps over SQL and RDF Online at www.reengineeringllc.com Shared use is free, and there are no advertisements Adrian Walker Reengineering On Sun, Jun 23, 2013 at 12:49 PM, Gregg Reynolds d...@mobileink.com wrote: Hi folks, A couple of years ago I got the idea of finding alternatives to the official definition of RDF, especially the semantics. I've always found the official docs less than crystal clear, and have always harbored the suspicion that the model-theoretic definition of RDF semantics offered in http://www.w3.org/TR/rdf-mt/ was unnecessary, or at least unnecessarily complicated. Needless to say that is my own personal aesthetic judgment, but it did motivate my little project. I guess the past two years have not been completely wasted on me; what was a somewhat vague intuition back then seems to have matured into a pretty clear idea of how RDF ought to be conceptualized and formally defined. Clear to me, anyway; whether it is to others, and whether it is correct or not is a whole 'nother matter. Since pursuing this idea will involve a lot of writing I won't pursue it here; instead I've described the the basic ideas in a blog post at http://blog.mobileink.com/. The allusion to Wittgenstein, that great philosophical therapist, is entirely intentional. You (or at least I) find out a lot of things when you analyze a concept very closely; if my analysis is not mistaken, there are some fundamental problems in the land of RDF. For example, it is possible to show, among other things, that the concept of a graph is not essential to RDF; nor is the treatment of the Property node of a triple as an arrow or relation necessary; nor is the concrete semantics defined in the RDF Semantics document the only or even the best theory of RDF. (Maybe this is all obvious to the cognoscenti, but insistence that RDF just is a graph is very common.) On the positive side, thinking about RDF as a mathematical domain (or domains), independent of RDF as a language, leads to a pretty substantial improvement in clarity; and since it requires a certain amount of creativity it's just fun. The reason I'm posting this here is because I will need some help, especially from real mathematicians and logicians. A category theorist, for example. Not only to check my reasoning; my hope is that others interested in pursuing this line of thought might come up with yet other fresh ideas. Plus, I've had a lot of fun thinking along those lines, and since a lot of people on this list spend a lot of time thinking about RDF (among other things), I thought they might find it interesting and fun as well. The plan is to post a series of blog articles fleshing out the ideas in coming months, so if anybody would like to help or collaborate please let me know. Cheers, Gregg Reynolds
Re: RDF Investigations
Hello Gregg, my remarks: -Classical logic is called classical for a reason -There may be different ways to think about RDF abstract syntax but those other ways IMO will not provide additional value. Other useful logics, for example many-valued logic, require additional syntactic elements. -The RDF syntax is incomplete ? You cannot construct a contructive calculus for triples and graphs from the rules in the specification ? I don't believe this. -RDF does not specify an inferential calculus ? The RDF semantics document contains an inferential calculus for RDF and RDFS entailment and a proof that they are correct and complete: http://www.w3.org/TR/rdf-mt/#rules Regards, Michael Brunnbauer On Sun, Jun 23, 2013 at 11:49:17AM -0500, Gregg Reynolds wrote: Hi folks, A couple of years ago I got the idea of finding alternatives to the official definition of RDF, especially the semantics. I've always found the official docs less than crystal clear, and have always harbored the suspicion that the model-theoretic definition of RDF semantics offered in http://www.w3.org/TR/rdf-mt/ was unnecessary, or at least unnecessarily complicated. Needless to say that is my own personal aesthetic judgment, but it did motivate my little project. I guess the past two years have not been completely wasted on me; what was a somewhat vague intuition back then seems to have matured into a pretty clear idea of how RDF ought to be conceptualized and formally defined. Clear to me, anyway; whether it is to others, and whether it is correct or not is a whole 'nother matter. Since pursuing this idea will involve a lot of writing I won't pursue it here; instead I've described the the basic ideas in a blog post at http://blog.mobileink.com/. The allusion to Wittgenstein, that great philosophical therapist, is entirely intentional. You (or at least I) find out a lot of things when you analyze a concept very closely; if my analysis is not mistaken, there are some fundamental problems in the land of RDF. For example, it is possible to show, among other things, that the concept of a graph is not essential to RDF; nor is the treatment of the Property node of a triple as an arrow or relation necessary; nor is the concrete semantics defined in the RDF Semantics document the only or even the best theory of RDF. (Maybe this is all obvious to the cognoscenti, but insistence that RDF just is a graph is very common.) On the positive side, thinking about RDF as a mathematical domain (or domains), independent of RDF as a language, leads to a pretty substantial improvement in clarity; and since it requires a certain amount of creativity it's just fun. The reason I'm posting this here is because I will need some help, especially from real mathematicians and logicians. A category theorist, for example. Not only to check my reasoning; my hope is that others interested in pursuing this line of thought might come up with yet other fresh ideas. Plus, I've had a lot of fun thinking along those lines, and since a lot of people on this list spend a lot of time thinking about RDF (among other things), I thought they might find it interesting and fun as well. The plan is to post a series of blog articles fleshing out the ideas in coming months, so if anybody would like to help or collaborate please let me know. Cheers, Gregg Reynolds -- ++ Michael Brunnbauer ++ netEstate GmbH ++ Geisenhausener Straße 11a ++ 81379 München ++ Tel +49 89 32 19 77 80 ++ Fax +49 89 32 19 77 89 ++ E-Mail bru...@netestate.de ++ http://www.netestate.de/ ++ ++ Sitz: München, HRB Nr.142452 (Handelsregister B München) ++ USt-IdNr. DE221033342 ++ Geschäftsführer: Michael Brunnbauer, Franz Brunnbauer ++ Prokurist: Dipl. Kfm. (Univ.) Markus Hendel pgpjzw8AQgXB6.pgp Description: PGP signature
