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Re: What do the ontologists want?

From: David Allsopp <dallsopp@signal.dera.gov.uk>
Date: Wed, 16 May 2001 11:29:26 +0100
Message-ID: <3B025686.CA80D72B@signal.dera.gov.uk>
To: Jim Hendler <jhendler@darpa.mil>
CC: www-rdf-logic@w3.org

Jim Hendler wrote:

> actually, although we've been discussing this a lot in DAML+OIL
> committee (under the name tagging) I've come to realize that there's
> a better way to do this in the ontology world -- define an ontology
> in which objects have these properties and use them -- the languge is
> then in the standard, but different communities can work on different
> tagging schemes
> Essentially, create a DAML ontology with
> Agent:Message :a daml:class .
> Agent:TimeStamp :a daml:property
>    rdfs:range  Agent:Message
>    rdfs:domain <define your own or use XML datatype>  .
> etc.
> Later, you use instances of these in the obvious way
> Agent:Message11111988 :a Agent:Message
>   Agent: TimeStamp "4:00PM Tuesday"    [or your favorite]  .
> You can now have relatively arbitrary data structures, they're in a
> relatively stable language parsable with either RDF or XML tools, and
> you can exchange things freely with colleagues using various DAML or
> RDF tools.

That's very interesting (and the term 'tagging' hopefully avoids some of
the stating/quoting/reifying confusion) I have some questions...

As I understand it, you attach a timestamp property to the message
object (a resource of type Message); but I'd assume that we intend to
say that the timestamp applies to all individual statements within that

If so, how are these statements (the actual message content) 'contained'
by the message object, since it can't point at them without reification? 

For example, we have the triples

message_01 --rdf:type--> agent:Message
message_01 --agent:timeStamp--> "4:00PM Tuesday"

and the content of the message, such as:

Airport_01 --status--> Operational

How do we assemble these such that we know that the timestamp 
appies to the content? Or do we associate the two by convention?

(One could nest a serialized RDF/DAML document within the message object
(i.e have a 'content' property that points to a rather long string
literal) but that doesn't seem to be what you're suggesting).

Alternatively, the description of the Message object merely accompanies
other statements in a document, and it is up to the recipient to notice
it and take appropriate implementation-dependent action.

Or perhaps I have misunderstood the intended usage; I want to be able,
in principle, to determine the timestamp, origin etc of any individual
statement about any resource in my database/RDF Model. I am unclear how
or if putting a timestamp on a message object would translate to a
timestamps on its constituent statements (which are gathered together
along with those from many other messages in some form of database).


David Allsopp
DERA Malvern

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Received on Wednesday, 16 May 2001 06:33:46 UTC

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