- From: Alan Rector <rector@cs.man.ac.uk>
- Date: Wed, 23 May 2007 09:51:57 +0100
- To: Chris Mungall <cjm@fruitfly.org>
- Cc: Phillip Lord <phillip.lord@newcastle.ac.uk>, Marijke Keet <keet@inf.unibz.it>, public-semweb-lifesci@w3.org
On 21 May 2007, at 19:50, Chris Mungall wrote: > > > On May 20, 2007, at 11:49 PM, Alan Rector wrote: > >> >> Chris >> >> >> On 18 May 2007, at 18:10, Chris Mungall wrote: >> >> >>> >>> I'm afraid I'm unclear how to state the OWL n-ary relation pattern >>> (http://www.w3.org/TR/swbp-n-aryRelations) where I really need >>> it. In all the examples given, the "lifted"[*] n-ary relation was >>> never truly a relation in the first place and always better >>> modeled as a class. It's kind of cheating. What if my n-ary >>> relation is transitive or if the 3rd argument is a temporal >>> interval over which the relation holds? >>> >>> I think the former is doable with property role chains. Updating >>> the n-ary relations note with this - and all the other omitted >>> details, such as how to re-represent domain/range, functional >>> properties, n-ary relations in restrictions etc - would take a >>> lot of work and would make it utterly terrifying to the naive user. >>> >>> Nevertheless the results are clunky and will need special tool >>> support[**] to avoid going insane. >> >> I'd love to see DLR or similar means worked into future versions >> of OWL or other standards, although I am not the one to comment on >> the logical/complexity issues. I certainly agree that re- >> expresssing relations as properties carries a modest penalty by >> being more verbose, but it is manageable. >> >> To take the example in question for some relation R, let's take >> temperature as an example. I shall use the subrelations >> "has_feature" / "has_state" to minimise arguments over what is, >> and is not a "quality" - an issue not germane to this discussion. >> Also I will use "has_state" as the property name so we don't have >> both a property "has_value" and a keyword VALUE. >> >> In the binary relation form in manchester simplfied syntax in OWL >> 1.0 we have: >> >> Organism has_feature SOME (Temperature_Feature THAT >> has_temporal_extent VALUE temporal_extent_1 AND >> has_state SOME (has_magnitude VALUE 37 AND has_units VALUE >> degrees_C)) >> >> where temporal_extent_1 is an individual which has facts >> has_start_time VALUE n AND has_end_time VALUE m. >> has_magnitude is a functional datatype property and has_units is >> a functional property. For the record, I accidentally left this ambiguous as to whether it was "Organisms that a temperature of 37C during temopral extent 1" Organism THAT has_feature. SOME (... or the claim, better as "This class of organism has the temperature feature during temporal extent 1" "ThisOrganismClass --> has_feature SOME (... Should be > > Here Temperature_Feature is a "history" (sensu Hayes) or a time- > slice. Do I have this correct? Deliberately left ambiguous to limit the number of cardinaltiy constraints to explain. It depends on the cardinality of is_feature_of. I had not put a max 1 cardinality constraint on it, implying that there can be many features, but any feature at any time. For most purposes the inferences are the same. However, to expand the example. If you want features to be 4-D objects that have values at a time, then each entity has at most one of each feature and each feature has one state at each time. If you want a 3-D view then each entity has exactly one of each kind of feature at a given time, and the feature has exactly one state. If you want either view exclusively, there is no need for History entities. Whichever way you do it, you need to express the cardinality constraints someplace. e.g. 4D Entity --> has_feature MAX 1 Temperature_feature is_feature_of: FUNCTIONAL (Feature AND has_time_point SOME Time_point) has_state MAX 1 State. e.g. 3D (Entity AND has_time_point SOME Time_point) has_feature MAX 1 Temperature_feature. has_state: FUNCTIONAL is_feature_of: FUNCTIONAL If you want to add something like "Situation" to the 3D view, you can do it be substituting (Entity AND in_situation (Situation THAT has_time_point SOME Time_point)) has_feature MAX 1 Temperature_feature. > > This sort of thing can always be made to work if the relevant > concessions are made in the upper ontology. For example, in the > above I never talk of qualities-as-continuants, but only through > their histories. To my mind this complicates things a lot - unless > you fully embrace the 4D view of the world. So the consequence of the representation using histories is complication. What is the advantage? > > What about for relations such as part of and location? For example, > a protein that is in the cytoplasm at a certain time: > > Protein that has_feature SOME (Location_Feature THAT > has_temporal_extent VALUE temporal_extent_1 AND > has_location SOME cytoplasm) > > Would this be a fair extrapolation? > > Would the following be accurate for a 4D representation of the same > thing? > > Protein that has_history SOME (History THAT > has_temporal_extent VALUE temporal_extent_1 AND > has_location(4d) SOME (History THAT history_of SOME cytoplasm) This seems suspect to me, but I am not clear what your underlying model is or what you want to infer. It seems to say that histories are located in histories which seems odd. And it is unclear to me what you gain by the more complex representation. Let's go back to basics. What is the statement in plane English? I presume: "A protein that is located in some cytoplasm during some temporal extent" What inferences do you want to draw about the Protein? the Cytoplasm? the History of each? What inferences do you wish to make that you cannot make from the simpler representations? What else do you need to say that can be expressed with Histories that cannot be expressed in the simpler representation? > >> where n,m are date-time expressions, for simplicity let us assume >> integers representing milliseconds since some reference point. > > Fair enough. A lot of the time you wouldn't have an ordinal scale > but rather a partial ordering, but this doesn't affect the design > pattern > >> Inn OWL 1.1 we can do quite a bit better - although again there is >> a need for improved tools to make it easier. >> >> * An organism has a given temperature at some point in an interval >> >> anOrganism --> >> has_feature SOME (Temperature_feature THAT >> has_time_point SOME (has_coordinate SOME int[>=n, <m]) >> has_state... >> >> * An organism has a given temperature throughout an interval. >> (This has to be expressed as "Any temperature feature of the >> individual anOrganism in the time interval has the given state" >> >> Temperature_feature THAT >> is_had_by VALUE anOrganism AND >> has_time_point (Some has_coordinate SOME int[>=n, <m]) --> >> has_state... >> >> where is_time_point_of: inverse has_time_point >> has_time_point: functional >> Axiom: (Feature THAT has_time_point SOME Time_point) has_value >> Max 1 State. >> has_coordinate is used here with int since I am assuming it is >> measured in "ticks since basepoint", but could equally well be a >> float >> >> >> >>> Nevertheless the results are clunky and will need special tool >>> support[**] to avoid going insane. In general I am wary of design >>> pattern type things - they are usually a sign that the language >>> lacks the constructs required to express things unambiguously and >>> concisely. >> >> Separate "unambiguously" and "concisely". Whether or not there is >> something ambiguous about a design pattern depends on the case. >> In this case I think there is no ambiguity. "Concisely" is a >> matter for tools and layered "higher level languages". >> >> The history of computing is the history of "design patterns" at >> one level that eventually get built into "higher level languages" >> at the next level of abstraction up. > > I think I have a less optimistic view of progress in computer > science. For example, many of the paradigmatic GoF design patterns > are there to make up for deficiencies in the OO languages that > *succeeded* more expressive and abstract functional languages. Change is not always monotonic improvement, but I'll maintain the general point over the long trajectory of language and computing development. Also it is not linear but a partial ordering. Not everything from one branch affects the others. Alan > >> No one would argue against layoring more convenient languages on >> top of OWL ( or its successors). The patterns are a first step >> towards this end, just as they were in the early days of >> programming languages. Neither would anyone argue against more >> expressive languages. >> >> But I would argue that building on known, tested, and proven >> semantics and computational methods is preferable to inventing new >> ones. I'd rather spend my time on improving tooling for something >> well-understood, standardised, and supported by a community of >> specialists than on trying to invent something new on my own that >> was likely to be none of these things. I'll invent when I have >> to - when I am convinced that the best available methods do not >> meet mission critical needs. But I take a lot of convincing, and >> even if convinced I will build out from the well understood >> foundations wherever possible, with just enough extra invention to >> do what is required. > > I don't think I would disagree here > >> I speak from experience. I've done both. >> >> Regards >> >> Alan >> >> ----------------------- >> Alan Rector >> Professor of Medical Informatics >> School of Computer Science >> University of Manchester >> Manchester M13 9PL, UK >> TEL +44 (0) 161 275 6149/6188 >> FAX +44 (0) 161 275 6204 >> www.cs.man.ac.uk/mig >> www.clinical-esciences.org >> www.co-ode.org >> >> >> >> > > ----------------------- Alan Rector Professor of Medical Informatics School of Computer Science University of Manchester Manchester M13 9PL, UK TEL +44 (0) 161 275 6149/6188 FAX +44 (0) 161 275 6204 www.cs.man.ac.uk/mig www.clinical-esciences.org www.co-ode.org
Received on Wednesday, 23 May 2007 08:52:07 UTC