DB 5 -- Element "example" not allowed inside element "article" ?

Hi All,

I am trying to insert an element "example" inside "article"; however, I 
get the following error message in the XML editor (I am using oXygen XML 
editor):
element "example" from namespace "http://docbook.org/ns/docbook" not 
allowed in this context

However, per information on:
http://www.oasis-open.org/docbook/documentation/reference/html/example.html

I see "example" has a parent "article"

Please advise.

Thank you,
Anagha
PS: I am using DocBook 5, the article element appears as: <article 
xmlns="http://docbook.org/ns/docbook" version="5.0"> in my xml file.