XOM API for Processing XML with Java

[Gregory Garretson <gregory AT garretson.info>]

Michael Kay wrote:

> > Why is an Attribute a Node that has a ParentNode as a parent, 
> > as returned by attribute.getParent(), but at the same time 
> > it's not a child of a ParentNode, as returned by parent.getChild(n)?
> >    
>
> When people ask that question of the XPath model, my usual response is: it
> was a mistake to use the word "parent" for the relationship between a node
> and its owner, given that (a) we expect parent to be the inverse
> relationship of child, and (b) we expect things to have two parents, not
> one.
>  
Actually, I think you're confusing two problems that come from different 
sources. The expectation that things will have two parents is a problem 
that comes with the use of the "parent-child" analogy to describe trees. 
However, since it is very well established in computer science (and 
graph theory) to speak of a tree in terms of parent and child nodes, it 
isn't a bigger problem here than it is anywhere else, which, I would 
argue, is still not much.

On the other hand, I think that your point (a) is very good; even in 
comp sci, we typically expect the parent-child relationship to be a 
reciprocal one, so if c.getParent() returns p, then we should expect 
p.getChild(n) to return c for some n. Perhaps there should be a 
different name for getParent(), as John suggests. But then there's the 
inheritance problem that Mike C. brings up. Sorry I don't have any good 
suggestions...

Gregory