When you declare an element in the site structure, the definition of the element ID is not required. If you omit it, RIFE will look at the XML filename of the element declaration and use the base part for the element ID.

For example, the following definition:

<element file="element/engine/simple.xml" url="/simple"/>

is exactly the same as:

<element id ="simple" file="element/engine/simple.xml" url="/simple"/>