Use of org.freedesktop.DBus.Error

[Thomas Downing]

Two simple questions:

1. where can I find the specification for org.freedesktop.DBus.Error?  Or a list 
of all the defined error names for the same (e.g. UnknownMethod, etc.).

2. If a process experiences an error while servicing a method call, but it is 
not a fatal error (the process is still consistent and operating), what is the 
prefered error name under org.freedesktop.DBus.Error, if there is such?

Thanks,

Thomas Downing