Re: It's pizza-time again

"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message news:409673ba$0$562$e4fe514c_at_news.xs4all.nl...
> Dawn M. Wolthuis wrote:
>
> >>x wrote:
> >>mAsterdam wrote:
> >>
> >>>This was just an introduction to expand on my uneasy feeling
> >>>towards equating 'thing' and 'fact'.
> >>>
> >>>In that context I also used a distinction:
> >>>
> >>>_thing_ :
> >>>pizza, topping, table, clock, customer, onion, order, order-item.
> >>>(now I am not so sure about the last two).
> >>>
> >>>_fact_ :
> >>>"It's 4 p.m", "We are out of onions",
> >>>"the customer at table 12 ordered 2 neapolitan icecreams".
> >>
> >>From these lists I would infer:
> >>_thing_ = "material" noun.
> >> _fact_ = occured event, occurence
> >>
> >>Sounds like the distinction between TO BE and TO OCCUR
> >
> >
> > I think of it as a difference between IS (a thing, an entity) and IS
TRUE (a
> > proposition, predicate). So, when talking about "files" the name and
> > description of the file describe the entity and the attributes are
> > considered information about that entity -- something that "IS". If we
have
> > a PERSON entity/file/function, then GENDER is an attribute of that
PERSON,
> > that entity that IS.
>
> But the "file" would contain many OCURRENCES of PERSON, no?

PERSON can be thought of as a RELATION or a function mapping A KEY (could be compound) to a tuple. But it could also be a function variable (relvar) where the function itself varies depending on the keys in the "domain of the function" and the tuples in the range. That is typically how we view PERSON, for example, when we are doing data modeling. So, is a RELVAR an entity? We could define it that way. Then an ENTITY would be a variable? Yup, I'd go for that. I think that works for an XML entity too.

def. entity:
An entity is a variable whose values are functions (or relations)

In RM then we would be saying that RELVAR=entity rather than a single row being an entity (it would be a possible value for the entity, or a possible single domain & range value within the value of the entity), for example. We use the term "ENTITY" related to the old terms of file, record, or field, depending on the context, but considering it a variable works for all of these.

Then if CLASS is a variable (which some call it) and an OBJECT is a value, ... it was clear a second ago, but now I've hit a cloud, so I'll come back to it when my view is not obstructed by my brain. --dawn <snip> Received on Mon May 03 2004 - 19:09:45 CEST