This is the runtime identifier used for accessing the object being defined.

There are some pre-defined object identifiers listed below.

bb        Backing bean or code behind

top       object on top of the stack

Since this is the identifier at runtime, the naming convention would be as dictated by the platform. That is, whether camel case, or other formats are in use.

For Struts, this identifier would end up in the configuration file, for form beans.