Re: General semantics

From: Clifford Heath <>
Date: Fri, 21 May 2010 15:57:56 +1000
Message-ID: <4bf620e6$0$32019$>

paul c wrote:
> By unary relation I mean a relation with one attribute (which I think is
> pretty standard lingo, surprised that anybody here wouldn't think that)

Right, that's what I thought you meant. In which case, it could be a representation of either an existential fact type (an object type), or a unary predicate over one. The distinction is important. A unary predicate creates a subset of the object type it involves.

This distinction was, I believe, the cause of your earlier disagreement.

Further, a unary fact type does not have to be mapped as a unary relation. It could be represented as a boolean value in a table of that object type.  

> but I have no idea what a 'fact type' is. I know of relation and tuple
> types but don't know what use terms like 'fact type' or 'unary fact'
> terms might have.

Fact oriented modeling has a parallel history with relational modeling. It's built on logic rather than sets; those are two sides of one coin. Needless to say, it has its own terminology - I tried to introduce some. It's a different perspective, equal in power and purity to RM. It has some advantages in mapping to natural language somewhat better. See for more details. Ignore it, or look into it, but don't scoff at it until you've looked into it. Received on Fri May 21 2010 - 07:57:56 CEST

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