Why does this work

<dtml-call "_['testadd'].manage_addDTMLMethod('MethodId', 'Method Title','method text')">

While this does not:

<dtml-call "_['testadd'].manage_addZSQLMethod('ZSQLID', 'ZSQL Title', 'DB','','select * from data')">

Error Type: AttributeError Error Value: manage_addZSQLMethod

I studies the Znolk product and found that it uses _setObject directly instead of manage_addZSQLMethod .

In general there is an inconsistency in adding objects: sometimes you can use the manage_addYourProduct interface, and sometimes only going through the addProduct invocation (don't have the whole thing handy here) will do the trick. This can get very confusing. Wouldn't know if that's the matter here, though. I think this should be standardized in the interfaces.

but it IMHO the visibility of manage_addDTMLMethod and manage_addZSQLMethod _should_ be the same ?

I agree