The new definition of Within

The spatial relationship methods in the the previous version (May 5, 1999) were defined in terms of the 9-intersection matrix. Although they were sometimes counterintuitive - for example coincident points would not be pass the Equals test - they were unambiguous. The new version (Nov 22, 2005) has moved away from that to natural language definitions. This is unfortunate, because natural language is inherently ambiguous. I fear that some unintended changes may have crept in, but it is hard to tell.

The new definition of Equals is "TRUE if g1 is completely contained in g2". The old definition - translated to my natural language - was "TRUE if g1 is contained IN THE INTERIOR OF g2". The change is significant, because the methods are no longer a classification. For example, a point on the boundary of a polygon will now satisfy both Touches and Within, whereas it only satisfied Touches by the old spec. Is this change intentional?


The new definition of Within

Correction... Due to the cross-wired links, I was looking at the Implementation Specification thinking that it was a new version of the Types and Functions spec.

So let me rephrase my comment:

Two coincident points satisfy the definition of Within in the current "Simple Features - SQL - Types and Functions (1.1)" document. Of course, one cannot argue with a definition... but I suspect that this is an oversight - they also satisfy Equals. The clause "and the intersection of I(b) with E(a) is not empty" should be added to the set-theoretical definition. In terms the 9-string it should be "a.Relate(b,