Konsep Inti
It is decidable whether a given deterministic attributed tree transducer with monadic output can be realized by an equivalent deterministic top-down tree transducer with look-ahead.
Abstrak
The paper addresses the problem of deciding whether a given deterministic attributed tree transducer (datt) with monadic output can be realized by an equivalent deterministic top-down tree transducer (dtR) with look-ahead.
The key insights are:
If a dtR is equivalent to a datt, then the datt must have the "single path property" - i.e., the attributes of the datt only process nodes along a single path in the input tree.
The authors construct an associated dattR (B, A') from the given datt A, where the attributes of A' also only process nodes along a single path, similar to the states of the dtR.
They show that the dattR (B, A') can be converted into a two-way transducer TW, and then apply the result from prior work that decides whether a two-way transducer can be realized by an equivalent one-way transducer.
If a one-way transducer equivalent to TW exists, then the authors show how to construct a dtR equivalent to the original datt A.
The paper also extends the results to nondeterministic attributed tree transducers with "look-around" and monadic output, showing that it is still decidable whether an equivalent dtR exists.