phone (one-based):this type of identifier is used throughout the toolkit; it can be converted to a phone name via an OpenFst symbol table. Not necessarily contiguous (the toolkit allows "skips" in the phone indices).
hmm-state (zero-based): this is an index into something of type HmmTopology::TopologyEntry. In the normal case, it is one of {0, 1, 2}.
pdf, or pdf-id (zero-based):this is the index of the p.d.f., as originally alloca