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Re: [ontolog-forum] Ontology of Rough Sets

To: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Ronald Stamper <stamper.measur@xxxxxxxxx>
Date: Wed, 26 Jan 2011 11:10:44 +0000
Message-id: <4F23F276-3B25-4CFA-BF24-8BB2B90CBF3F@xxxxxxxxx>
I spoke of *enabling* the reliability of verifying the information, leaving the strictness of verification to be decided according to the actual situation.

Your intention to talk to Chris next week does not become false a week later having forgotten about your undertaking.  The expressed intention, as a result of discourse norms, will have produced in others expectations by which they will judge you and according to which you will decide how to act when you look in your diary and register your mistake.  

A record that it is raining without also the relevant time being recorded or known from the context would not deserve the trouble taken to gauge its truth value.  In the realm of practical affairs we deal with truth at a certain time.

Presentism demands a concern for times, provenance for the information and for knowledge of the agents responsible for the information.  There are practical limits to the thoroughness of any response to these concerns; but it is important not to overlook them.

Regards,

Ronald 


On 26 Jan 2011, at 01:56, Pat Hayes wrote:


On Jan 25, 2011, at 5:57 PM, Ronald Stamper wrote:

Dear Pat,

Presentism has the advantage for the study of information systems of forcing one to recognise that knowledge of things in the world that do not exist now can be known only via signs that stand for them.

Actually I think this applies to everything, existent now or not. All knowledge is known via signs. Arguably (cognitive scientists argue about this) all of our knowledge consists of signs inside our heads. 

Those signs do exist now.  They can be inspected.  They should include references to those agents responsible for the signs as well as for the model of the present reality to enable the reliability of all that information to be verified, as far as possible.  

Why? For some purposes very strict verification is important, for many others it is less so. I don't see this as being any kind of uniform overarching requirement on all notational systems. 

You make presentism sound like a dumb idea

For representing knowledge which is temporally sensitive, it is a very dumb idea. If I write "must talk to Chris next week" in my diary and wait a week, it has become false simply by the passage of time. If I write "it is raining" the sentence can become false in minutes. Not a good way to manage data, I submit. 

Pat

whereas it forces us to manage the present stock of physical data and to make explicit our dependence on the responsible agents who supply our information.

A presentist system risks becoming over complicated unless it can employ a highly succinct language.

Ronald Stamper 


On 25 Jan 2011, at 22:40, Pat Hayes wrote:


On Jan 25, 2011, at 10:10 AM, Matthew West wrote:

Dear Pat,
 
You  said:
 
And I guess I have to defer to you when it comes to databases. But then I wonder why there has ever been a notion of, for example, a temporal database? After all, if database classes can change with time, why do we need to do anything special to make them 'temporal' ?
 
There are at least two things going on here. Firstly, the whole point of databases is that you can add records to them. Of course as soon as you do, in principle you have a different ontology (or whatever you want to call it). However, that is OK, because what you want is an ontology of how things are now.

You do??? What an extraordinary idea. Seriously: surely almost any real-world data management task needs to keep track of what is true 'now' AND what was true previously. Medical records, for example, and customer records of purchases, and stock control, and, well, just about anything. But my main bother with what you say is the idea that an *ontology* can even be said to be true 'now' at all. Surely ontologies themselves should be timeless. This is not to say that they cannot be improved and changed as models change, of course; but the idea of using actual computer clock time to be an ontological record for the time of information seems to me to be unworkable. This would be a 'presentist' ontology. It would have the worldview of a lower mammal which has no idea of time but lives only in the present moment, like Robert Burn's fieldmouse. 

 
The idea of a temporal database is one where you not only know how things are now, but also how things were in the past, so you know about the changes that have happened as well as the current state, for example, a customer’s old address as well as their current one.

They also carefully distinguish 'valid' time - the time referred to by the data - from 'transaction' time - the time the data was inserted into the database; thereby even more clearly rejecting a simple 'presentist' model. 

 
There may also be other types of temporality, such as time indexed measurements.
 
Regards
 
Matthew West                            
Information  Junction
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From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Pat Hayes
Sent: 25 January 2011 08:04
To: [ontolog-forum] 
Subject: Re: [ontolog-forum] Ontology of Rough Sets
 
 
On Jan 22, 2011, at 8:58 PM, Christopher Menzel wrote:


On Jan 22, 2011, at 6:47 PM, Pat Hayes wrote:
On Jan 22, 2011, at 4:50 PM, Christopher Menzel wrote:

...A class can change its membership from one interpretation to another merely with the addition or removal of statements.
 
Sure.

i'm not sure I agree, and I wonder if Chris really does.
 
I don't. I hastily read Doug's claim to be the rather trivial claim that a class can change its membership from one interpretation to another by the addition or removal of elements from its extension.


What does this even mean, "a class can change its membership from one interpretation to another" ? A given class NAME may be interpreted differently in different interpretations, of course: but the classes themselves - the entities, whatever they are, which are denoted by the class names and which are, therefore, classes - cannot "change ... membership from one interpretation to another" since they ARE entities in a given interpretation. It does not make sense to speak of 'moving' a class (or anything else) 'from' one interpretation 'to' another.
 
I'm not following. Suppose I have a class name c in my language and let M be an OWL interpretation in which c denotes OWL class C. Now create a new interpretation M' that differs from M only in that we alter the extension that is assigned to c's denotation C. Doesn't that make credible sense of the idea that C's members have changed?
 
I guess that does make a kind of sense, provided we are all agreed that we are talking within the Common Logic model theory. But it would not make sense if we were using classical Tarskian semantics or, for example, the OWL normative semantics. And I think it is a misleading way of speaking, since it is easily misunderstood as saying that one can take a set and change its members (and it still be the same set....)



And even if it did, how would this be achieved by addition or removal of STATEMENTS? Classes do not (usually) contain statements.
 
Agreed.
 
That said, (2) does seem to be a strong *intuitive* idea in the KR, AI, and database communities.
 
This is the meaning i was referring to.
 
Never meant to suggest otherwise! :-)

Then allow me to suggest otherwise. As someone somewhat familiar with at least the KR and AI communities, I do not recall that the idea that class membership can change is, in fact, a strong intuitive idea there. If it were, the AI/KR field would have been happily using class language rather than, say, speaking of situations, ever since 1969. Temporal reasoners use many formal devices to represent time and change, but this simplistic notion of classes changing their membership is not one of them. If one were to try to use it in a realistic example, one would rapidly discover why.
 
I'll defer to you vis-á-vis the AI community; perhaps I've overgeneralized there.  But in my own experience building "real world" database models and ontology models, I often heard folks talking about classes changing membership. Notably, in an implementation of a database model, intuitively, the instances of the classes identified in the model change with every update.
 
And I guess I have to defer to you when it comes to databases. But then I wonder why there has ever been a notion of, for example, a temporal database? After all, if database classes can change with time, why do we need to do anything special to make them 'temporal' ?
 
Pat
 
 
-chris
 
 
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