Re: [xml-dev] Incongruous UML data models and XSD data models

[Michael Kay <mike@saxonica.com>]

The "nested boxes" graphical representation of a hierarchy can sometimes be useful, and it has the advantage of providing a direct visual representation of a "containment" relationship. In dealing with document structures, some people will recognize its use in "clause analysis".

One problem (but that's true of most graphical representations of trees) is that it doesn't scale well - you quickly run out of paper.

However, the tree metaphor for a data structure is very readily understood and very ancient - it goes back at least to the tree of Jesse in Isaiah.

Michael Kay
Saxonica


> In trying to teach [about] XML, I think we all tend at some stage to
> have used the tree as a reference, which is a pity, because the
> classical "family-tree" diagram of XML is upside down: really more of a
> root-system.
> 
> Near&Far did at least present its diagram sideways, but I think that may
> have been because it's more usual to have XML documents with greater
> width (siblings, represented vertically) than depth (descendants,
> represented horizontally). If you have to start adding non-element
> nodes, the whole tree-metaphor becomes unreadably dense.
> 
> How are most of the people we want to present a graphical model to
> at understanding different-shaped boxes joined by lines anyway?
>