[ Re-posting this message, in plain text, so everyone can have fine
grain access (deep linking) to the message in the archive ... my
apologies for getting it out wrong earlier. =ppy ] (01)
I'm relocating this very interesting thread from the [oor-forum] which
started yesterday over here - ref. thread starting with message:
http://ontolog.cim3.net/forum/oor-forum/2011-10/msg00008.html (02)
I've made a best attempt to roll up the exchanges so far below. (03)
... please continue the discussion on this forum. (04)
----------
From: Ali SH <asaegyn+out@xxxxxxxxx>
Date: Wed, Oct 19, 2011 at 9:07 AM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: Bijan Parsia <bparsia@xxxxxxxxxxxx>
Cc: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx> (05)
Hi Bijan, (06)
[AH] Allow me to attempt re-phrasing what's been said. In
contrast to a paradigm for ontologies like Cyc, whereby one tries to
model the domain as faithfully and completely in one formalism and
then delegates reasoning tasks based on the analysis of this
expressive representation; (07)
[BP] Is that how Cyc works? That's not my understanding, but whatever :) (08)
I over simplified and in fact cringed after reading the sent email.
What I meant to contrast is that in many ways Cyc is an example of a
paradigm which represents the domain in an expressive language and
then finds the appropriate subsets that match decidable logics for
reasoning. At least, that's my understanding. It uses a variety of
reasoners. (09)
[BP] The problem with super expressive logics such as Common Logic
is, roughly, the tool support sucks and probably sucks for the
forseeable future. (010)
I would hope that with the current work under way by the Bremen group
(HeTS) and the Toronto group (COLORE), a CL ontology could be factored
into more tractable fragments. Of course, not to mention a number of
CL reasoners currently under development and the environment being
developed by CameronRoss. Needless to say, I'm more optimistic about
utilizing more expressive languages. (011)
On Wed, Oct 19, 2011 at 11:42 AM, Bijan Parsia <bparsia@xxxxxxxxxxxx> wrote: (012)
In the end, it shouldn't really affect what you're trying to do.
If you need to represent something, you need to represent it. If you
put it in your "ontology" rather than in your "rule base", but the
answers are the same, does it *really* matter? (013)
Admittedly, the surface language might end up not mattering much, but
I certainly was confused as to what people meant by Rule, and
clarifications such as this thread can help avoid pointless future
confusion when talking to different groups of people :D. Further, in
the context of the OOR and using the OMV to tag various registered
ontologies and create web-services and workflows around what is in the
OOR, these distinctions could come to bear. (014)
Presumably, we're going to see more OWL+SWRL or RIF ontologies being
deployed and registered in the repository. How will the SWRL or RIF
modules be stored and what is the nature of their relationship (using
OMV or an extension) to the OWL ontologies? What is the nature of a
subset of some CL ontology that maps to some OWL+SWRL combo? And so
on. To what extent can these mappings be automated and tools /
services orchestrated to solve ontology related problems for
reseachers / professionals? (015)
Indeed, in the conference call earlier this week
(http://ontolog.cim3.net/cgi-bin/wiki.pl?OOR/ConferenceCall_2011_10_18),
I think there was a suggestion for rules should be stored
externally(?). The sense I got was that not everyone involved in the
discussion was clear about the distinction between rules / axioms, so
it seems rather relevant. (016)
Best,
Ali (017)
_________________________________________________________________ (018)
----------
From: Bijan Parsia <bparsia@xxxxxxxxxxxx>
Date: Wed, Oct 19, 2011 at 8:42 AM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>,
Ali SH <asaegyn+out@xxxxxxxxx> (019)
On 19 Oct 2011, at 16:20, Ali SH wrote:
> Dear Pat and Bijan,
>
> On Tue, Oct 18, 2011 at 6:52 PM, Pat Hayes <phayes@xxxxxxx> wrote:
>
>> Guys, you have to adapt your terminology to the people you are trying to
>communicate with. In the OWL/RDF/RIF/Semantic-Web/LInked-Data world, there is
>no such thing as an 'inference rule'. (If there were, it would be a line of
>code inside an inference engine; but most inference engines don't work that
>way in any case, but instead build tableaux. The textbook terminology of
>formal logic has not been used in the applied ontology world for about the
>last two decades.)
>
> Thank you for your discussion and clarification, it's been very helpful!
> Allow me to attempt re-phrasing what's been said. In contrast to a paradigm
>for ontologies like Cyc, whereby one tries to model the domain as faithfully
>and completely in one formalism and then delegates reasoning tasks based on
>the analysis of this expressive representation; (020)
Is that how Cyc works? That's not my understanding, but whatever :) (021)
> in this context we have more of a bottom-up, a priori engineered approach? (022)
No? (023)
> Before you begin your representation, you partition your domain into
>different types of knowledge and use a variety of representation / rule
>languages to capture different parts of intuitions. Simplifying greatly, does
>this fairly capture the essence of the paradigm? (024)
Not for me. (025)
I'd put it this way in both cases: You pick your language based on a
variety of factors, most likely what your overly-enthusiastic friend
forces on you, then do the best you can with the toolset available.
With a formalism like OWL, we've made a basic tradeoff of expressivity
in favor of computability (plus some other choices to improve
usability). So, we have a nice set of tools that work rather well and
an expanding suite of services (cf recent work on explanation or
module extraction/dependency analysis). Our problem is that we have to
work around expressivity limitations. A danger is that our world view
becomes warped to those limitations. (026)
The problem with super expressive logics such as Common Logic is,
roughly, the tool support sucks and probably sucks for the forseeable
future. (FOL reasoners are superawesome, but I still can't get a
simple formalization of the Allan calculus in terms of "meets" to
verify before o before -> before! The usual line I get from by FOL ATP
peeps is "So, what decidable fragment does it fall into.) The
advantage is, of course, expressivity (which can be a disadvantage,
too, of course): You can say what you need to say, mostly, and usually
rather directly. The problem is that you can't do much with it or
check it very well. If you do use tools you often end up having to
warp your representation to those tools. (Cf Rieter's Knowledge In
Action for a very clever and systematic way of doing it...most of the
time it's not so nice.) (027)
Pick your poison :) (028)
> All this said, I'm still a touch flummoxed at being able to adequately and
>consistently distinguish an axiom from a rule. For example, the standard
>inheritance / subclass relation of:
>
> (forall (x) (if (dog x) (animal x)))
>
> is supported by virtually all DL's. It seems like it could be a rule to me. (029)
In logics with a deduction theorem (or subsets there of) the
distinction isn't big. (030)
> I mean, Pellet or Racer would be able to use the class structure in an OWL-DL
>ontology to tell me that the properties of Animals apply to Dogs. (031)
But they use a refutation mechanism, not "triggering" the rule. (032)
In the end, I don't think the distinction in a general sense is worth
getting all as worked up about it as many rule folks do. Just consider
the particular formalism you are dealing with, note the syntax and
semantics and how the commonly used proof procedures work, and move
on. That it's a "RULE" language or *not* a rule language is, well,
meh. Or, rather, mostly ideological. (033)
>
> [PH] So, now, let us switch back to logical terminology, and I will put
>scare quotes around the earlier usages. Are 'rules' axioms? Yes, pretty much,
>if we are talking baout the Horn-clause style of rule; although there are
>'rule' languages which allow one to say things that cannot be said in normal
>logics, eg default assumptions, negation-by-failure, closed-world
>presumptions, etc.. (034)
> and (035)
> [BP] No as true anymore [re inference rules]. "Consequence" based
>reasoning is becoming more popular esp. in restricted fragments such as EL,
>e.g., (036)
> Given these two statements, and putting aside the sociological issues for a
>moment, in this case, one can determine whether something is a "rule" really
>only in the context of the expressivity of a particular representation
>language? Roughly, anything that can't be represented in the formalism is
>considered a rule? (037)
That would make rule langauges odd. (038)
The simple rule of thumb is the union of horn clauses with implicitly
univerisally quantified explicit variables (usually with variables
bound to names) or IF-THEN productiony conditions is a rule.
Everything else is not. Some non rules are equivalent to some rules. (039)
> I.e. say I want to represent a fragment of law, I can only decide what is a
>rule by first deciding which formalism and reasoner I'm using, then anything
>that couldn't be expressed in said language is a candidate for a rule? (040)
Or you could just not care. That its a rule in some generalized sense
is really quite pointless. That it can be expressed in the formalism
that you want to use is important. (041)
> In summary, what one means by a rule is wholly dependent on what
>representation language one deploys? (042)
No, my summary is: Don't get hung up on this bit of terminology. It's
not remotely helpful. (043)
> Other people I've spoken to suggest that there is fundamentally something
>distinct about the notion of a rule from what should be contained in an
>ontology, which seems like a different issue altogether? (044)
They are wrong. (045)
> They suggest that "concepts and rules" should be treated separately. (046)
This seems to be, at best, at a different level of conceptualization
than the formalism. (047)
> The description provided by Pat seem more to do with engineering, while those
>in the previous sentences hinge on a particular interpretation of ontology. (048)
Yeah, I wouldn't get hung up on what an "ontology" is either. Yet
Another Rathole. (049)
In the end, it shouldn't really affect what you're trying to do. If
you need to represent something, you need to represent it. If you put
it in your "ontology" rather than in your "rule base", but the answers
are the same, does it *really* matter? (050)
Cheers,
Bijan. (051)
_________________________________________________________________ (052)
----------
From: Ali SH <asaegyn+out@xxxxxxxxx>
Date: Wed, Oct 19, 2011 at 8:20 AM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: Pat Hayes <phayes@xxxxxxx>
Cc: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx> (053)
Dear Pat and Bijan, (054)
On Tue, Oct 18, 2011 at 6:52 PM, Pat Hayes <phayes@xxxxxxx> wrote: (055)
Guys, you have to adapt your terminology to the people you are
trying to communicate with. In the
OWL/RDF/RIF/Semantic-Web/LInked-Data world, there is no such thing as
an 'inference rule'. (If there were, it would be a line of code
inside an inference engine; but most inference engines don't work that
way in any case, but instead build tableaux. The textbook terminology
of formal logic has not been used in the applied ontology world for
about the last two decades.) (056)
Thank you for your discussion and clarification, it's been very helpful! (057)
Allow me to attempt re-phrasing what's been said. In contrast to a
paradigm for ontologies like Cyc, whereby one tries to model the
domain as faithfully and completely in one formalism and then
delegates reasoning tasks based on the analysis of this expressive
representation; in this context we have more of a bottom-up, a priori
engineered approach? Before you begin your representation, you
partition your domain into different types of knowledge and use a
variety of representation / rule languages to capture different parts
of intuitions. Simplifying greatly, does this fairly capture the
essence of the paradigm? (058)
All this said, I'm still a touch flummoxed at being able to adequately
and consistently distinguish an axiom from a rule. For example, the
standard inheritance / subclass relation of: (059)
(forall (x) (if (dog x) (animal x))) (060)
is supported by virtually all DL's. It seems like it could be a rule
to me. I mean, Pellet or Racer would be able to use the class
structure in an OWL-DL ontology to tell me that the properties of
Animals apply to Dogs. (061)
[PH] So, now, let us switch back to logical terminology, and I
will put scare quotes around the earlier usages. Are 'rules' axioms?
Yes, pretty much, if we are talking baout the Horn-clause style of
rule; although there are 'rule' languages which allow one to say
things that cannot be said in normal logics, eg default assumptions,
negation-by-failure, closed-world presumptions, etc.. (062)
and (063)
[BP] No as true anymore [re inference rules]. "Consequence" based
reasoning is becoming more popular esp. in restricted fragments such
as EL, e.g., (064)
Given these two statements, and putting aside the sociological issues
for a moment, in this case, one can determine whether something is a
"rule" really only in the context of the expressivity of a particular
representation language? Roughly, anything that can't be represented
in the formalism is considered a rule? I.e. say I want to represent a
fragment of law, I can only decide what is a rule by first deciding
which formalism and reasoner I'm using, then anything that couldn't be
expressed in said language is a candidate for a rule? (065)
In summary, what one means by a rule is wholly dependent on what
representation language one deploys? (066)
Other people I've spoken to suggest that there is fundamentally
something distinct about the notion of a rule from what should be
contained in an ontology, which seems like a different issue
altogether? They suggest that "concepts and rules" should be treated
separately. The description provided by Pat seem more to do with
engineering, while those in the previous sentences hinge on a
particular interpretation of ontology. (067)
Thanks,
Ali (068)
_________________________________________________________________ (069)
----------
From: Christopher Menzel <cmenzel@xxxxxxxx>
Date: Wed, Oct 19, 2011 at 2:22 AM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: Pat Hayes <phayes@xxxxxxx>
Cc: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>,
Ali SH <asaegyn+out@xxxxxxxxx> (070)
On Oct 19, 2011, at 12:52 AM, Pat Hayes wrote:
> Guys, you have to adapt your terminology to the people you are trying to
>communicate with. In the OWL/RDF/RIF/Semantic-Web/LInked-Data world, there is
>no such thing as an 'inference rule'. (071)
Pat, I believe I adapted my terminology quite precisely to the people
I was trying to communicate with, namely, Ali and interested
observers. :-) My purpose was nothing grander than to note the
ambiguity of "rule" in the sense he was talking about and the use of
"rule" in logic. As I noted in my post: (072)
> The senses of "rule" you describe for the most part seem rather different. (073)
That said, your lengthy discourse (with Bijan's qualifications) was
very informative. (074)
-chris (075)
_________________________________________________________________ (076)
----------
From: Kathryn B Laskey <klaskey@xxxxxxx>
Date: Tue, Oct 18, 2011 at 6:11 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx> (077)
Well said. Thanks -- i was planning to write something similar but am
too swamped to get to it. (078)
On Oct 18, 2011, at 6:52 PM, Pat Hayes wrote: (079)
> Guys, you have to adapt your terminology to the people you are trying to
>communicate with. ...[snip]... (080)
_________________________________________________________________ (081)
----------
From: Bijan Parsia <bparsia@xxxxxxxxxxxx>
Date: Tue, Oct 18, 2011 at 5:12 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: Pat Hayes <phayes@xxxxxxx>
Cc: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>,
Ali SH <asaegyn+out@xxxxxxxxx> (082)
On 19 Oct 2011, at 00:59, Pat Hayes wrote: (083)
> Bijans quibbles are all quite correct, (084)
Indeed! :) (085)
> but I plead that I was trying to get across a basic almost sociological
>divide here (and was talking to logicians) and there wasnt time to go into too
>much detail. (086)
Sure. Just amending where I thought some more detail would help. Tastes vary. (087)
And you are definitely on the side of angels at the moment (ducks). (088)
> He is also quite right that OWL2 refers to "axioms", a fact I had simply
>forgotten. Its unusual, though, in this respect. Calling them axioms is by no
>means, um, axiomatic. (089)
Indeed. But I think it's winning :) In rdf land, "triples" is by far
preferred for many of the same reasons. (090)
> One counter-quibble: (091)
For what do we live, but to make quibble fodder for our neighbours,
and quibble at them in our turn? (092)
> On Oct 18, 2011, at 6:34 PM, Bijan Parsia wrote:
>
>> On 18 Oct 2011, at 23:52, Pat Hayes wrote:
>>
>> .....
>> [snip]
>>> Still, there has been widespread interest in extending the expressive power
>of a DL logic by adding some of the functionality of a rule language to it.
>This has the great appeal of keeping the DL fragment intact while allowing
>inference engines to step outside the DL world where needed,
>>
>> Er...why isn't this just "They are more expressive logics".
>
> Well, that is a very natural way to see it from a logically trained POV, I
>agree. But the sense I often get is that this not in fact how implementers see
>it, but more like using a rule engine to do quick patch-around hacks to
>overcome a local lack of expressivity (eg doing a very quick check for
>transitivity) (093)
This isn't my sense, qua implementor and friend of implementors,
*except* maybe for OWLRL and languages/implementations like that.
AL-log explicitly used a hybrid method, but while Pellet's rule
support used a Rete it was *inside* the tableau (and worked *on* the
completion graph). KAON2 reduced *everything* (DL axioms and DL Safe
rules alike) to disjunctive datalog KBs. HermiT's hypertableau
naturally incorporates horn kbs. (094)
There is no "quick" check for transitivity in *class expressions*, of
course. But over the named individuals and their relations to each
other it is faster to do datalogish reasoning, for obvious reasons. I
don't know of any OWL engine that does that, though. (095)
> but not even claiming any kind of completeness or attempting to relate the
>rules to the logical semantics in other than a superficial way. I dont accuse
>you or your colleagues of such sloppiness, of course, nor do I mean to say
>that more careful or theoretically sound work is not done; but there are
>certainly more, um, shall we say, scruffy points of view which just want to
>get things working as quickly as possible. (096)
Right, but my suggestion, sociologically, is that is more "from below"
than "from above", i.e., going from a rule based implementation of
RDFS to "some useful bit of OWL". These implementations are, of
course, not hybrid either, but purely rule based. (097)
> And my point in the email was only that Ali might well have come across some
>discussion from within that more engineering-oriented kind of tradition, is
>all. (098)
No worries ;) (099)
>> I'm not sure I see, from the generic inference engine POV, the difference
>between, e.g., adding transitivity to ALC and adding DL Safe rules.
>(Obviously, from an implementation perspective, they are quite different. Some
>are sometimes amenable some of the time to hybrid proof procedures, but those
>aren't even always preferred these days, at least, in the sense of bolting
>together separatedly developed engines).
>
> Quite. I was talking about the bolting-together approach. (0100)
Yes, this is the point of clarification. The bolting together is
really quite rare nowadays (though, interesting, current Pellet +
Stardog the rdf store have some of this): If you have a DL engine with
rules, it's as likely to be designed for rules (due to Boris Motik,
mostly). If you don't, you likely just have a rules engine with some
random axiomitzation of some fragment of OWL. (0101)
(Or you're in the polynomial DL space, where the two approachs
coincide, really.) (0102)
Cheers,
Bijan. (0103)
_________________________________________________________________ (0104)
----------
From: Pat Hayes <phayes@xxxxxxx>
Date: Tue, Oct 18, 2011 at 4:59 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>,
Bijan Parsia <bparsia@xxxxxxxxxxxx>
Cc: Ali SH <asaegyn+out@xxxxxxxxx> (0105)
Bijans quibbles are all quite correct, but I plead that I was trying
to get across a basic almost sociological divide here (and was talking
to logicians) and there wasnt time to go into too much detail. He is
also quite right that OWL2 refers to "axioms", a fact I had simply
forgotten. Its unusual, though, in this respect. Calling them axioms
is by no means, um, axiomatic. (0106)
One counter-quibble: (0107)
On Oct 18, 2011, at 6:34 PM, Bijan Parsia wrote: (0108)
> On 18 Oct 2011, at 23:52, Pat Hayes wrote:
>
> .....
> [snip]
>> Still, there has been widespread interest in extending the expressive power
>of a DL logic by adding some of the functionality of a rule language to it.
>This has the great appeal of keeping the DL fragment intact while allowing
>inference engines to step outside the DL world where needed,
>
> Er...why isn't this just "They are more expressive logics". (0109)
Well, that is a very natural way to see it from a logically trained
POV, I agree. But the sense I often get is that this not in fact how
implementers see it, but more like using a rule engine to do quick
patch-around hacks to overcome a local lack of expressivity (eg doing
a very quick check for transitivity) but not even claiming any kind of
completeness or attempting to relate the rules to the logical
semantics in other than a superficial way. I dont accuse you or your
colleagues of such sloppiness, of course, nor do I mean to say that
more careful or theoretically sound work is not done; but there are
certainly more, um, shall we say, scruffy points of view which just
want to get things working as quickly as possible. And my point in the
email was only that Ali might well have come across some discussion
from within that more engineering-oriented kind of tradition, is all. (0110)
> I'm not sure I see, from the generic inference engine POV, the difference
>between, e.g., adding transitivity to ALC and adding DL Safe rules.
>(Obviously, from an implementation perspective, they are quite different. Some
>are sometimes amenable some of the time to hybrid proof procedures, but those
>aren't even always preferred these days, at least, in the sense of bolting
>together separatedly developed engines). (0111)
Quite. I was talking about the bolting-together approach. (0112)
Pat (0113)
>
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_________________________________________________________________ (0116)
----------
From: Bijan Parsia <bparsia@xxxxxxxxxxxx>
Date: Tue, Oct 18, 2011 at 4:34 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>
Cc: Ali SH <asaegyn+out@xxxxxxxxx> (0117)
On 18 Oct 2011, at 23:52, Pat Hayes wrote:
> Guys, you have to adapt your terminology to the people you are trying to
>communicate with. In the OWL/RDF/RIF/Semantic-Web/LInked-Data world, there is
>no such thing as an 'inference rule'. (If there were, it would be a line of
>code inside an inference engine; but most inference engines don't work that
>way in any case, but instead build tableaux. (0118)
Not as true anymore. "Consequence" based reasoning is becoming more
popular esp. in restricted fragments such as EL, e.g., (0119)
Frantisek Simancik, Yevgeny Kazakov, Ian Horrocks: Consequence-Based
Reasoning beyond Horn Ontologies. IJCAI 2011: 1093-1098 (0120)
Yevgeny Kazakov, Markus Krötzsch, Frantisek Simancik: Unchain My EL
Reasoner. Description Logics 2011 (0121)
(KAON2 had a related technique applies to SHIQ kbs. (0122)
Plus, Tableaux (or tree methods) typically work by deriving logical
consequences (i.e., representatives of models or contradictions). (0123)
> The textbook terminology of formal logic has not been used in the applied
>ontology world for about the last two decades.) (0124)
Ehhhhh. The distinction between a inference rule and, more generally,
a proof theory/procedure/system and an object sentence/axiom/wff is
alive and well. Plenty of areas of formal logic tend not to focus on
"inference rules" per se. (0125)
> That is not what the people that Ali is citing are talking about. In the
>applied-semantic-web world, traditional logics are not widely used, in fact
>hardly at all. The most widely used formalisms are description logics; so
>widely used in fact that for many people, DL's simply *are* the 'language' for
>writing ontologies, and the very idea of an ontology written any anything
>other than a DL (except maybe something even less expressive, such as RDF) is
>not even contemplated or mentioned. (0126)
I quibble. As extensions to OWL are continually proposed, explored,
and debated, it's really far too strong to say that alternatives are
not on the horizon. Many modellers treat whatever language they know
and have a tool for as exhaustive of the possibilities, but that's
often true regardless of the language. OWL/RDF/RDFS, being rather
popular, just mean that they loom larger on the horizon and modellers
are not forced to contemplate alternatives. (0127)
> However, this world does recognize another class of notations, loosely
>derived from Prolog or from production systems (which were developed entirely
>separately from logics and so share almost no scholarly or terminological
>links with the logic field), (0128)
I'll grant you production systems, but not Prolog. Programming with
Logic, after all :) Plus the relationship between relational
databases, datalog, and Prolog and first order logic are quite
standardly discussed. (0129)
The main difference is less heterogeneity of basic proof procedure in
the Prolog/Datalog world: Resolution is king in a way that it's not
for even for FOL ATP anymore. (0130)
> which operate by chaining together 'rules' (basically, and oversimplifying,
>Horn clauses thought of as encoding forward-constrained implications). (0131)
Since you lampshade the oversimplification, I forgive it :) (0132)
> So there is a large and active field which develops, studies and categorizes
>"rule languages" which range in complexity from simple Horn-clause
>forward-inference engines to elaborate things with defaults, exceptions and so
>on. There is also a usage of "rule" as in 'business rule', and an active area
>of formalization and standardization for these 'rules' , in which they are
>seen as essentially deontic rules, encoding normative ways to behave rather
>than facts which are true or false. And these are still considered to be
>'rules' and 'rule languages'. So it is not obvious that it all reduces to Horn
>clauses in every case. (Merging an assertional with a deontic language would
>be an interesting challenge.) And then there are logic-programming systems
>like Prolog, and production systems. All of these have a great deal in common
>at the implementation level, so they have come to be seen as parts of a single
>field of 'rule languages', one which now holds its own conferences, journals,
>standardization committees, etc.. etc..(For example, try googling RuleML.) (0133)
In expert systems, esp. deriving from production system, "inference
rule" often means a domain specific encapsulation of a reasoning
pattern such as the relation between a test result and the probabiltiy
of a disease or metacognitive advice such as if the diagnosis
confidence is low, perform another test. Indeed, any law likeish
generalization, as opposed to concrete facts. (0134)
> Both of these formalisms - description logics and rule languages - can be
>viewed as subcases of FOL (as indeed can relational DBases) and this point of
>view often seems obvious or trivial to logicians, but it is far from obvious
>in practice, (0135)
Actually, not even in theory. Finite (for datebases) and
preferred/minimal model theory are both complex and have lots of
profundity (e.g., descriptive complexity). (0136)
> especially as these fields have developed rather different ways to be
>practically useful. DL restricts the logical expressivity to a decideable
>subset of FOL with the finite model property, (0137)
Quibble: Not quite. SHIQ et al do not have the finite model property
per se (since its possible to encode structures with infinite
descending chains, i.e., descendent relations). But they do have
something which is called various things but basically that you have
an associated structure which is finite (in SHIQ's case, basically,
every infinite model becomes regular after a certain size, so cycle
detection (called "Blocking") can ensure termination). (0138)
[snip] (0139)
> Still, there has been widespread interest in extending the expressive power
>of a DL logic by adding some of the functionality of a rule language to it.
>This has the great appeal of keeping the DL fragment intact while allowing
>inference engines to step outside the DL world where needed, (0140)
Er...why isn't this just "They are more expressive logics". I'm not
sure I see, from the generic inference engine POV, the difference
between, e.g., adding transitivity to ALC and adding DL Safe rules.
(Obviously, from an implementation perspective, they are quite
different. Some are sometimes amenable some of the time to hybrid
proof procedures, but those aren't even always preferred these days,
at least, in the sense of bolting together separatedly developed
engines). (0141)
[snip] (0142)
> So, now, let us switch back to logical terminology, and I will put scare
>quotes around the earlier usages. Are 'rules' axioms? Yes, pretty much, if we
>are talking baout the Horn-clause style of rule; (0143)
Even in bog standard FOL, we can admit extended derived rules (e.g.,
by allowing a substitution rule onto theorems). As I recall from my
intro to symbolic logic days, this is done in textbooks to reduce the
size of the proof theory from a metalogical point of view while still
allowing a reasonably convenient proof system. (Plus progressive
exercises: Proof double negation using modus pones and indirect proof
or whatnot). (0144)
> although there are 'rule' languages which allow one to say things that cannot
>be said in normal logics, eg default assumptions, negation-by-failure,
>closed-world presumptions, etc.. However, that terminology of 'axiom' would
>be anathematic in the ontology world. (0145)
http://www.w3.org/TR/owl2-syntax/#Introduction (0146)
OWL 2 ontologies consist of the following three different syntactic
categories:.... (0147)
Axioms are statements that are asserted to be true in the domain being
described. For example, using a subclass axiom, one can state that the
class a:Student is a subclass of the class a:Person. (0148)
http://www.w3.org/TR/owl2-syntax/#Axioms (0149)
Etc. (0150)
Worse, and my bad, we all now use them for entailments, i.e.,
"Entailed axiom". Oh well. (0151)
> It smacks of mathematics (which ontology engineering most definitely is not)
>and it carries the presumption of being an 'assumed truth', which again is
>inappropriate in this other world. It would be much better to say, statement
>or expression or sentence, rather than axiom. (0152)
My experience, which let me to write that above bit, is that people
found "statement" and "sentence" confusing because it *wasn't*
distinct enough. "Axiom" is more like "line of code": the difference
helps keep clear what we're talking about (and prevents people from
thinking they understand when they don't). YMMV. (0153)
> But yes, many 'rules' are sentences, in fact sentences of the form ((A and B
>and C) imply D), where A--D are atomic sentences.
>
>> When people refer to an ontology (or an ontology artifact), are they
>referring singularly to (a) the axioms, or (b) the axioms under deductive >
>closure, or (c) the axioms in combination(s) with reasoner(s)?
>
> In the OWL/RDF world, definitely (a). However, don't call them 'axioms',
>please. (0154)
Unless you quote the spec :) (0155)
Cheers,
Bijan. (0156)
_________________________________________________________________ (0157)
----------
From: Pat Hayes <phayes@xxxxxxx>
Date: Tue, Oct 18, 2011 at 3:52 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>,
Ali SH <asaegyn+out@xxxxxxxxx> (0158)
Guys, you have to adapt your terminology to the people you are trying
to communicate with. In the OWL/RDF/RIF/Semantic-Web/Linked-Data
world, there is no such thing as an 'inference rule'. (If there were,
it would be a line of code inside an inference engine; but most
inference engines don't work that way in any case, but instead build
tableaux. The textbook terminology of formal logic has not been used
in the applied ontology world for about the last two decades.) (0159)
That is not what the people that Ali is citing are talking about. In
the applied-semantic-web world, traditional logics are not widely
used, in fact hardly at all. The most widely used formalisms are
description logics; so widely used in fact that for many people, DL's
simply *are* the 'language' for writing ontologies, and the very idea
of an ontology written any anything other than a DL (except maybe
something even less expressive, such as RDF) is not even contemplated
or mentioned. However, this world does recognize another class of
notations, loosely derived from Prolog or from production systems
(which were developed entirely separately from logics and so share
almost no scholarly or terminological links with the logic field),
which operate by chaining together 'rules' (basically, and
oversimplifying, Horn clauses thought of as encoding
forward-constrained implications). So there is a large and active
field which develops, studies and categorizes "rule languages" which
range in complexity from simple Horn-clause forward-inference engines
to elaborate things with defaults, exceptions and so on. There is also
a usage of "rule" as in 'business rule', and an active area of
formalization and standardization for these 'rules' , in which they
are seen as essentially deontic rules, encoding normative ways to
behave rather than facts which are true or false. And these are still
considered to be 'rules' and 'rule languages'. So it is not obvious
that it all reduces to Horn clauses in every case. (Merging an
assertional with a deontic language would be an interesting
challenge.) And then there are logic-programming systems like Prolog,
and production systems. All of these have a great deal in common at
the implementation level, so they have come to be seen as parts of a
single field of 'rule languages', one which now holds its own
conferences, journals, standardization committees, etc.. etc..(For
example, try googling RuleML.) (0160)
Both of these formalisms - description logics and rule languages -
can be viewed as subcases of FOL (as indeed can relational DBases) and
this point of view often seems obvious or trivial to logicians, but it
is far from obvious in practice, especially as these fields have
developed rather different ways to be practically useful. DL restricts
the logical expressivity to a decideable subset of FOL with the finite
model property, and its paradigmatic tableaux reasoners achieve
completeness within this decidable sub case. (There is a big
theoretical literature recording the history and logical ramifications
of all this, with links to modal logics and a great deal of advanced
model theory.) The rule language tradition is far less logically based
and more pragmatic: it typically pays no attention at all to
completeness ( OK, I know there are exceptions, but they are achieved
only by warping the semantics) and often thinks of the rule languages
as more like programming languages than logics. (0161)
Still, there has been widespread interest in extending the expressive
power of a DL logic by adding some of the functionality of a rule
language to it. This has the great appeal of keeping the DL fragment
intact while allowing inference engines to step outside the DL world
where needed, without sacrificing the guarantees of decideability
provided by the use of the DL fragment to do the basic consistency
chacking which supports practical ontology entailment. Such hybrids
have been being proposed, implemented and used since the beginning of
the semantic web effort. (0162)
I think this is what the sources cited by Ali are referring to. S (0163)
So, now, let us switch back to logical terminology, and I will put
scare quotes around the earlier usages. Are 'rules' axioms? Yes,
pretty much, if we are talking baout the Horn-clause style of rule;
although there are 'rule' languages which allow one to say things that
cannot be said in normal logics, eg default assumptions,
negation-by-failure, closed-world presumptions, etc.. However, that
terminology of 'axiom' would be anathematic in the ontology world. It
smacks of mathematics (which ontology engineering most definitely is
not) and it carries the presumption of being an 'assumed truth', which
again is inappropriate in this other world. It would be much better to
say, statement or expression or sentence, rather than axiom. But yes,
many 'rules' are sentences, in fact sentences of the form ((A and B
and C) imply D), where A--D are atomic sentences. (0164)
> When people refer to an ontology (or an ontology artifact), are they
>referring singularly to (a) the axioms, or (b) the axioms under deductive >
>closure, or (c) the axioms in combination(s) with reasoner(s)? (0165)
In the OWL/RDF world, definitely (a). However, don't call them 'axioms', please. (0166)
Pat Hayes (0167)
_________________________________________________________________ (0168)
----------
From: Ali SH <asaegyn+out@xxxxxxxxx>
Date: Tue, Oct 18, 2011 at 1:41 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: Christopher Menzel <cmenzel@xxxxxxxx>
Cc: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx> (0169)
On Tue, Oct 18, 2011 at 4:16 PM, Christopher Menzel <cmenzel@xxxxxxxx> wrote: (0170)
On Oct 18, 2011, at 10:06 PM, Ali SH wrote:
> Dear Leo and Chris,
>
> Thanks for the responses. I understand the distinction between
an inference rule and an axiom, (0171)
Right, as I'd suspected (and so noted at the bottom of my post). (0172)
Noted, but not acknowledged in my initial email response :D. (0173)
> the issue for me stems from a terminological confusion, because
obviously, an axiom can express a rule (not in the same sense as an
inference rule; i.e. if X is an employee then Y assigns X an employee
number). (0174)
Looks like an axiom to me. :-) "Rule" just seems to have a
pragmatic connotation that what is expressed is something that *ought*
to be done by whoever is playing a certain role (Y, presumably, in
this case). (0175)
In the LKIF paper, they have statements such as: (0176)
This is well explained in Deliverable D1.1, where LKIF itself is
discussed: for more complex or other types of knowledge than
terminological knowledge we also need rule formalisms. (page 3 in [1]) (0177)
There are also several rule-based approaches that try to capture
norms in rules with notions like violation or duty as antecedent or
conclusion. The rule itself captures the meaning of the norm, so that
the confusion between norm and normative statementis again retained.
(page 35 in [1]) (0178)
Which suggests to me that they aren't referring to inference rules.
But I have no clue how to reliably distinguish a rule from an axiom.
In [2] http://www.estrellaproject.org/doc/D1.1-LKIF-Specification.pdf,
they have a section describing their rules, which seems to me to be a
mix of axioms and inference rules. (0179)
For example, these seem like axioms to me (page 74 in [2]): (0180)
(rule §-9-306-1
(if (and (goods ?s ?c)
(consideration ?s ?p)
(collateral ?si ?c)
(collateral ?si ?p)
(holds (perfected ?si ?c) ?e)
(unless (applies §-9-306-3-2 (perfected ?si ?p))))
(holds (perfected ?si ?c) ?e)))
(rule §-9-306-2a
(if (and (goods ?t ?c)
(collateral ?s ?c))
(not (terminates ?t (security-interest ?s)))))
(fact F1 (not (terminates T1 (security-interest S1))))
(fact F2 (collateral S1 C1)) (0181)
> That said, your interpretation of rule poses an interesting
question, do people distinguish an ontology from an ontology +
whatever inference rules used to interpret it? (0182)
Inference rules simply come packaged with whatever logic one is
building one's ontology on (or affixing one's ontology axioms to). (0183)
That's what I thought. (0184)
> Based on analogy then, does gmail as software refer to the gmail
the source code, or gmail the compiled, deployed code? (0185)
Sorry, man, that's too heavy for me! :-) (0186)
I have a feeling this question has been tread before.... ;) (0187)
> When people refer to an ontology (or an ontology artifact), are
they referring singularly to (a) the axioms, or (b) the axioms under
deductive closure, or (c) the axioms in combination(s) with
reasoner(s)? (0188)
It seems to me that (a) and (b) are two viable meanings for
"ontology". (c) does not seem feasible to me, except insofar as one
identifies a reasoner with the logic it is based on. (0189)
This is where I guess the analogy with traditional software breaks
down. Gmail compiled and deployed seems to me to be (c). Though for
ontologies, the line between (b) and (c) are a bit unclear to me. I
don't know how someone (i.e. human) would be able to actually access /
generate (b) without some reasoner (their mind?). (0190)
[1] Joost Breuker, Rinke Hoekstra, Alexander Boer, Kasper van den
Berg, Rossella Rubino, Giovanni Sartor, Monica Palmirani, Adam Wyner,
and Trevor Bench-Capon. OWL ontology of basic legal concepts
(LKIF-Core). Deliverable 1.4, Estrella, 2007. (0191)
[2] Alexander Boer, Marcello Di Bello, Kasper van den Ber, Tom Gordon,
Andr´as F¨orh´ecz, R´eka Vas. Specification of the Legal Knowledge
Interchange Format. Deliverable 1.1, Estrella, 2007 (0192)
Best,
Ali
-- (0193)
(•`'·.¸(`'·.¸(•)¸.·'´)¸.·'´•) .,., (0194)
_________________________________________________________________ (0195)
----------
From: Christopher Menzel <cmenzel@xxxxxxxx>
Date: Tue, Oct 18, 2011 at 1:16 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: Ali SH <asaegyn+out@xxxxxxxxx>
Cc: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx> (0196)
On Oct 18, 2011, at 10:06 PM, Ali SH wrote:
> Dear Leo and Chris,
>
> Thanks for the responses. I understand the distinction between an inference
>rule and an axiom, (0197)
Right, as I'd suspected (and so noted at the bottom of my post). (0198)
> the issue for me stems from a terminological confusion, because obviously, an
>axiom can express a rule (not in the same sense as an inference rule; i.e. if
>X is an employee then Y assigns X an employee number). (0199)
Looks like an axiom to me. :-) "Rule" just seems to have a pragmatic
connotation that what is expressed is something that *ought* to be
done by whoever is playing a certain role (Y, presumably, in this
case). (0200)
> That said, your interpretation of rule poses an interesting question, do
>people distinguish an ontology from an ontology + whatever inference rules
>used to interpret it? (0201)
Inference rules simply come packaged with whatever logic one is
building one's ontology on (or affixing one's ontology axioms to). (0202)
> Based on analogy then, does gmail as software refer to the gmail the source
>code, or gmail the compiled, deployed code? (0203)
Sorry, man, that's too heavy for me! :-) (0204)
> When people refer to an ontology (or an ontology artifact), are they
>referring singularly to (a) the axioms, or (b) the axioms under deductive
>closure, or (c) the axioms in combination(s) with reasoner(s)? (0205)
It seems to me that (a) and (b) are two viable meanings for
"ontology". (c) does not seem feasible to me, except insofar as one
identifies a reasoner with the logic it is based on. (0206)
-chris (0207)
_________________________________________________________________ (0208)
----------
From: Ali SH <asaegyn+out@xxxxxxxxx>
Date: Tue, Oct 18, 2011 at 1:06 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>,
"Obrst, Leo J." <lobrst@xxxxxxxxx>, Christopher Menzel
<cmenzel@xxxxxxxx> (0209)
Dear Leo and Chris,
Thanks for the responses. I understand the distinction between an
inference rule and an axiom, the issue for me stems from a
terminological confusion, because obviously, an axiom can express a
rule (not in the same sense as an inference rule; i.e. if X is an
employee then Y assigns X an employee number).
That said, your interpretation of rule poses an interesting question,
do people distinguish an ontology from an ontology + whatever
inference rules used to interpret it? Based on analogy then, does
gmail as software refer to the gmail the source code, or gmail the
compiled, deployed code?
When people refer to an ontology (or an ontology artifact), are they
referring singularly to (a) the axioms, or (b) the axioms under
deductive closure, or (c) the axioms in combination(s) with
reasoner(s)?
I'd be curious to hear from Todd (or others who distinguish between
ontologies with and without rules) which sense of rule they refer to.
In my conversations with people, I don't believe they are referring to
"inference rule" when they distinguish between ontologies as not
having rules and some system that also has rules.
When people say that X doesn't have rules, do they mean that it can't
express something like (from wiki on RIF) (0210)
IF MARRIED(?x, ?y) THEN LOVES(?x, ?y) (0211)
or that the processing of the rule isn't part of the ontology?
Thanks,
Ali (0212)
_________________________________________________________________ (0213)
----------
From: Christopher Menzel <cmenzel@xxxxxxxx>
Date: Tue, Oct 18, 2011 at 12:38 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx> (0214)
On Oct 18, 2011, at 8:50 PM, Ali SH wrote:
> Hello Michael and all,
> I noticed some confusion today during the telecon when Michael and Todd were
>talking about differences between Ontologies & Theories, and Rules & Axioms.
>I've actually encountered a number of people who make this distinction -- that
>an ontology doesn't really express "rules", and that these rules are somehow
>different from "axioms". The line is still blurry to me, but it seems to be
>that in this terminology, a "rule" refers to anything that OWL doesn't
>support, whereas in the CL (and FOL world) there is no distinction between
>these "rules" and "axioms". (0215)
In logic, "rule" typically means "rule of inference". Together with
some set of logical axioms, rules are an essential part of a logical
system like propositional or first order logic. Thus, a standard set
of logical axiom (schemas) for propositional logic are: (0216)
(φ → (ψ → φ)
((φ → (ψ → θ)) → ((φ → ψ) → (φ → θ))
(¬φ → ψ) → ((¬φ → ¬ψ) → φ) (0217)
Note, however, that with axioms alone you are powerless to do anything
more than write down axioms. Rules of inference define a notion of one
sentence following from other and, hence, enables the derivation of
theorems that are not axioms. The usual rule of inference for
propositional logic, of course, is modus ponens: (0218)
MP: ψ follows from φ and φ → ψ. (0219)
A proof of propositional logic, then, is any sequence of sentences
such that each sentence is either an axiom or follows from sentences
occurring earlier in the sequence. (0220)
Predicate logic simply adds axioms for quantification, e.g., (0221)
∀αφ → φ(τ), where τ is an "acceptable" instance of φ
∀α(φ → ψ) → (φ → ∀αφ), where α does not occur free in φ (0222)
and, optionally, identity, and (typically) adds a rule of inference
for universal generalization: (0223)
UG: ∀αφ follows from φ. (Note this is usually qualified in certain
ways but never mind.) (0224)
CL, for better or worse, does not specify a proof theory but, if it
did, this is surely (?) what "rule" would mean. The senses of "rule"
you describe for the most part seem rather different. In my
experience, these "non-logical" uses of "rule" are usually synonymous
with "non-logical axiom". Speaking of which: (0225)
A first-order theory (in some first-order language) is any set of
non-logical axioms in the language of first-order logic. Peano
Arithmetic, Pat Hayes' ontology of liquids, etc are all first-order
theories. (0226)
I have a feeling you already knew this stuff but maybe someone else
will find it helpful. (0227)
-chris (0228)
_________________________________________________________________ (0229)
----------
From: Obrst, Leo J. <lobrst@xxxxxxxxx>
Date: Tue, Oct 18, 2011 at 12:35 PM
Subject: Re: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>,
Michael Gruninger <gruninger@xxxxxxxxxxxxxxx> (0230)
Ali and all, (0231)
Sorry I missed today, folks, just too busy these days. (0232)
I understand the notion of rule to be about the consequence relation,
e.g., modus ponens. A, A -> B |- B (where |- is syntactic consequence;
this is usually called entailment). This is at the meta-logic level.
These are often called “inference rules”. (0233)
An axiom (typically) uses the base logical connectives, and in this
case refers to (material) implication (conditional), e.g., (A /\
(A->B)) -> B. This is at the object (logic) level. (0234)
This is how I explain it to most of my students and others. Generally
rule-based systems or inference engines will use generalized modus
ponens, resolution, etc. (0235)
A deductive system can consist of axioms and inference rules, or
axioms only, or inference rules only. (0236)
Most folks bandy these terms around, and don’t make a clear
distinction between consequence and (material) implication. And you
will get a lot of gruff grief from people. (0237)
Modus Ponens: (0238)
X ® Y
X
------
Y (0239)
That inference rule is actually equivalent to: ((X ® Y) Ù X) ® Y (0240)
X Y X® Y ((X® Y) Ù X) ((X ® Y) Ù
X) ® Y
T T T T
T
T F F F
T
F T T F
T
F F T F
T (0241)
I have found the following to provide good descriptions (aside from
the usual books introducing logic or its meta-theory): (0242)
Hunter, Geoffrey. 1973. MetaLogic: An Introduction to the Metatheory
of Standard First Order Logic. University of California Press. (0243)
Ryan, Mark; Martin Sadler. 1992. Valuation Systems and Consequence
Relations. In: Abramsky, S.; Gabbay, Dov; Maibaum, T.S.E. Handbook of
Logic in Computer Science, Volume 1, Background: Mathematical
Structures. Oxford: Clarendon Press, pp. 1-78. (0244)
Concerning the difference between ontologies and theories: a group of
people will say that an ontology is just a logical theory, i.e., a
theory expressed in a logic. Others, philosophically realist, will say
that an ontology is a logical theory about some aspect of the real
world. I prefer the latter. (0245)
Other points: (0246)
If you look at SWRL, it is really a kind of Horn Logic/Rule
representation, i.e., a generalized Modus Ponens form used by logic
programming. RIF contains many notions of “rules” not just this kind
of “logical inference rule”, but production rules (forward-chaining
rules) from expert systems, etc. (0247)
Thanks, (0248)
Leo (0249)
_________________________________________________________________ (0250)
----------
From: Ali SH <asaegyn+out@xxxxxxxxx>
Date: Tue, Oct 18, 2011 at 11:50 AM
Subject: [oor-forum] Ontologies vs Theories / Axioms vs Rules
To: Michael Gruninger <gruninger@xxxxxxxxxxxxxxx>,
OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx> (0251)
Hello Michael and all, (0252)
I noticed some confusion today during the telecon when Michael and
Todd were talking about differences between Ontologies & Theories, and
Rules & Axioms. I've actually encountered a number of people who make
this distinction -- that an ontology doesn't really express "rules",
and that these rules are somehow different from "axioms". The line is
still blurry to me, but it seems to be that in this terminology, a
"rule" refers to anything that OWL doesn't support, whereas in the CL
(and FOL world) there is no distinction between these "rules" and
"axioms". (0253)
An example of such a distinction can be found in documentation re the
LKIF-Core (Legal Knowledge Interchange Format) ontology which makes
claims such as [1]
(http://www.estrellaproject.org/doc/D1.4-OWL-Ontology-of-Basic-Legal-Concepts.pdf): (0254)
We adhere to a rather restrictive view on what an ontology should
contain: terminological knowledge, i.e. intensional definitions of
concepts, represented as classes with which we interpret (model) the
world (page 7) (0255)
where things that would have other types of "rules" are part of
"frameworks" and not included as part of the ontology. (0256)
In these cases, it would still be possible to map from LKIF to a CL
ontology, but the reverse would either lose information or require the
selection LKIF and possibly one or more "frameworks" (perhaps stored
as OWL + RIF or SWRL combos in OOR). That said, I'm not sure what the
status of a RIF or SWRL module w/o an accompanying ontology would be
in the context of OOR, and how one would represent these combinations
using OMV. (0257)
Further, in their discussion of the deontics surrounding law, they state: (0258)
"Although the situation description may be expressed without
problems as a framework cast in OWL-DL, but OWL-DL does not allow this
deontic qualification to be expressed as a metaclass, or rather that
the deontic qualification allows reified statements. There are three
solutions to this problem. ... The second one is to express norms as
rules, which has an intuitive appeal, as in common sense terms legal
norms are synonymous with legal rules: one has to obey the rules.
However, this does not immediately solve the tractability problem
either as description logics and rule formalisms are not necessarily
compatible (see also [Boer et al., 2007])." (page 9) (0259)
I'm not certainly how prevalent these distinction between ontology,
theory, axiom and rules are, but I've come across it in (OWL heavy)
literature, and it is unclear to me whether such distinctions are
adequately covered by the OMV metadata. At the very least, if web
services will be built around the OOR platform, then this is an issue
that needs to be addressed. (0260)
Might someone help elucidate this distinction? (0261)
Best,
Ali (0262)
[1] Joost Breuker, Rinke Hoekstra, Alexander Boer, Kasper van den
Berg, Rossella Rubino, Giovanni Sartor, Monica Palmirani, Adam Wyner,
and Trevor Bench-Capon. OWL ontology of basic legal concepts
(LKIF-Core). Deliverable 1.4, Estrella, 2007.
-- (0263)
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