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Pushdown Transducer Library (PDTs)  
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# expand the (boundedstack) PDT into an FST keeping paths within a threshold of the best path pdtexpand weight=$threshold pdt_parentheses=pdt.parens >out.fst \ No newline at end of file  
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> > 

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Pushdown Transducer Library (PDTs)  
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A PDT is encoded as an FST, where some transitions are labeled with open or close parentheses. To be interpreted as a PDT, the parentheses must balance on a path.  
Changed:  
< <  See here for more information.  
> > 
A PDT is encoded as an FST where some transitions are labeled with open or close parentheses. To be interpreted as a PDT, the parentheses
must balance on a path. The subset of the transducer labels that correspond to parenthesis (open, closed) pairs is designated from the C++library in a
The following operations, many which have FST analogues (but are distinguished in C++ by having a
There are also delayed versions of these algorithms where possible. See the header files for additional information including options.
Note with this FSTbased representation of PDTs, many FST operations (e.g., As an example of this representation and these algorithms, the transducer in textual format:
fstcompile >pdt.fst <<EOF 0 1 1 1 1 0 3 3 0 2 0 0 2 3 2 2 3 2 4 4 2 EOF with parentheses:
cat >pdt.parens <<EOF 3 4 EOF
accepts This can be shown with:
$ fstcompile >1122.fst <<EOF 0 1 1 1 1 2 1 1 2 3 2 2 3 4 2 2 4 EOF # intersect the FST and PDT; the result is a PDT pdtcompose pdt_parentheses=pdt.parens pdt.fst 1122.fst  # expand the (boundedstack) PDT into an FST; this enforces the parenthesis matching pdtexpand pdt_parentheses=pdt.parens  # remove epsilons (formerly the parentheses) fstrmepsilon  fstprint 0 1 1 1 1 2 1 1 2 3 2 2 3 4 2 2 4
Had the input string been The above recognition algorithm has the exponential complexity of conventional PDT parsing. An alternate approach with cubic complexity, which is a generaliztion of Earley's algorihtm, is: # intersect the FST and PDT; the result is a PDT pdtcompose pdt_parentheses=pdt.parens pdt.fst 1122.fst  # find the shortest balanced path pdtshorestpath pdt_parentheses=pdt.parens  # remove epsilons (formerly the parentheses) fstrmepsilon  fstprint 0 1 1 1 1 2 1 1 2 3 2 2 3 4 2 2 4
Finally, the following invocation returns all paths within
# intersect the FST and PDT; the result is a PDT pdtcompose pdt_parentheses=pdt.parens pdt.fst in.fst  # expand the (boundedstack) PDT into an FST keeping paths within a threshold of the best path pdtexpand weight=$threshold pdt_parentheses=pdt.parens >out.fst  
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Pushdown Transducer Library (PDTs)  
Changed:  
< <  This is an experimental pushdown transducer (PDT) library. A PDT is encoded as an FST, where some transitions are labeled with open or close  
> >  This is a pushdown transducer (PDT) extension of the OpenFst library. A PDT is encoded as an FST, where some transitions are labeled with open or close  
parentheses. To be interpreted as a PDT, the parentheses must balance on a path.  
Changed:  
< <  This is an extension library of the OpenFst library. See here for more information.  
> >  See here for more information. 
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Changed:  
< <  Pushdown Transducers (PDTs)  
> >  Pushdown Transducer Library (PDTs)  
Changed:  
< <  This is an experimental pushdown transducer (PDT) library. A PDT is  
> >  This is an experimental pushdown transducer (PDT) library. A PDT is  
encoded as an FST, where some transitions are labeled with open or close parentheses. To be interpreted as a PDT, the parentheses must balance on a path.  
Changed:  
< <   CyrilAllauzen  07 Jun 2011  
> >  This is an extension library of the OpenFst library. See here for more information. 
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Pushdown Transducers (PDTs)  
Added:  
> >  This is an experimental pushdown transducer (PDT) library. A PDT is encoded as an FST, where some transitions are labeled with open or close parentheses. To be interpreted as a PDT, the parentheses must balance on a path.  
 CyrilAllauzen  07 Jun 2011 \ No newline at end of file 
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Added:  
> > 
Pushdown Transducers (PDTs)
 CyrilAllauzen  07 Jun 2011 