# Xml namespaces not in model with builder

**URL:** <https://www.ruby-forum.com/t/xml-namespaces-not-in-model-with-builder/116252>\
**Category:** Rails\
**Created:** [October 3, 2007, 9:49pm UTC](https://www.ruby-forum.com/t/xml-namespaces-not-in-model-with-builder/116252 "2007-10-03T21:49:47Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![karma\_guru](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@karma\_guru](https://www.ruby-forum.com/u/karma_guru)\
**Post date:** [October 3, 2007, 9:49pm UTC](https://www.ruby-forum.com/t/xml-namespaces-not-in-model-with-builder/116252/1 "2007-10-03T21:49:47Z")

</div>

I’m trying to grab some data from within a model and output it in xml.  
I’ve done this previously using the builder libs and it works a treat.

However, I’m trying to add xml with namespaces and get the following  
error:

Namespace prefix app on name is not defined

I’m trying to express the following:

app:name

\</app:name\>

name is the model and there is no reference to ‘app’ in my model. It  
is needed for the destination where the xml will be used.

I’m using xml.tag! ‘app:name’ as the colon causes issues and have  
tried the builder workaround for colons too with no success.

Does anyone know how I work around this?

Thanks!

-Paul