Firefox Addon - install.rdf - What does "em" mean in <em: description> ... </ em: description>

Question

What does em mean in

 <em:description>...</em:description> 

This is an excerpt from the addon install.rdf firefox file. I'm curious what the em part adds. I also could not find a solution to this on Google.

Answer 1

em is an XML namespace containing a description element. At the top of the install.rdf file, you should see this attribute:

 xmlns:em="http://www.mozilla.org/2004/em-rdf#" 

This tells the XML parser that the em prefix is ​​bound to this URI. This is what a particular description element gives, and how XML documents can have multiple description elements that do not conflict (by associating each description type with a different URI).