Re: General semantics

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 http://ormfoundation.org 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