[Zope] Newbie question

[David Lambert]

I am currently browsing the API Reference section of the Zope book and am 
trying simple examples. I am puzzled as to how various methods may be 
accessed from dtml. For instance the line:

<dtml-var expr="getSize()"> works fine, but:

<dtml-var expr="dow()"> (which I would have expected to return the day of 
week) gives an error

Obviously I am confused. Could somebody try and put me on the right tracks!

TIA

Dave.