[Zope] The XML-dtml notation "&dtml-variable;"

[Andrew]

Christopher Petrilli <petrilli@digicool.com> said: 
> On 11/4/99 11:31 AM, Michel Pelletier at michel@digicool.com wrote:
> 
> > Johan Carlsson wrote:
> >> 
> >> But, isn't there a way to supply a default value
> >> (if the variable lookup fails)?
> >> 
> >> Something like &dtml-variable default-value;
> > 
> > I think that would be stretching the semantics of <dtml-var> a bit
> > beyond where they should go.  Just wrap the entity in a <dtml-if> and
> > test for the variable existence beforehand.  Longer, but much more
> > clear.
> 
> Would something like this be more palatable?
> 
>     <dtml-var foo default="Empty">
> 

How is this different from the following?

<dtml-var foo null="default-value">


Drew