What names are known?

[G . B . Stott]

Hi there,

Here is a reasonably simple question fro someone who knows lout. The
standard version of file doc looks as follows when all comments are removed.

  @SysInclude { fontdefs        } # font definitions
  @SysInclude { langdefs        } # language definitions
  @SysInclude { dl              } # DocumentLayout package
  @SysInclude { docf            } # OrdinaryLayout extension
  @Include { mydefs }

@Use { @DocumentLayout }
@Use { @OrdinaryLayout }
@SysDatabase @RefStyle { refstyle }               # reference printing styles

Assuming mydefs is non-existent or empty, what names are known before the
first @Use? I'm not wanting all possible values: just an indication of the
sort of things that can occur within a definition (which has no import or
extend prefix) on the right hand side of a named parameter, say.

Barrie.