Ideas for Google Summer of Code/Flag diacritics in lttoolbox

Flag diacritics are a method used in the HFST tools to allow the writer of a transducer to exclude impossible analyses at run-time, where removing them from the transducer would explode its size. This would allow us to nicely handle languages with prefix inflection, or with circumfix inflection

Some work on Flag diacritics has already been made in lttoolbox-java.

Objectives

• Add support for flag diacritics to the .dix format.
• Add support for flag diacritics to lttoolbox
• Write a dictionary which demonstrates the use of flag diacritics (e.g. for Kurdish, Persian, Tajik, or some other language)

Coding challenge

• Write a dictionary in the lexc formalism which uses flag diacritics to treat a particular linguistic feature (e.g. verb prefixes in Indo-Iranian languages).

Format ideas

<dictionary>
  <alphabet/>
  <sdefs>
    <sdef n="verb"/>
    <sdef n="pres"/>
    <sdef n="past"/>
  </sdefs>
  <cdefs>
    <cdef n="ge:0" c="ge- prefix not present"/>
    <cdef n="ge:1" c="ge- prefix present"/>
  </cdefs>
  <pardefs>
    <pardef n="ge__prefix">
      <e><p><l></l><r/></r></p><c n="ge:0"/></e>
      <e><p><l>ge</l><r/></r></p><c n="ge:1"</e>
    </pardef>
    <pardef n="breek__vblex">
      <e><p><l/><r><s n="verb"/><s n="pres"/></r></p><c n="ge:0"/></e>
      <e><p><l/><r><s n="verb"/><s n="past"/></r></p><c n="ge:1"/></e>
    </pardef>
  </pardefs>
  <section id="main" type="standard">
    <e lm="breek"><par n="ge__prefix"/><i>breek</i><par n="breek__vblex"/></e>
  </section>
</dictionary>

Normal lt-expand output of this would look like:

breek:breek<verb><pres>
gebreek:breek<verb><past>

But if you showed the constraints, it would look like:

breek[ge:0][ge:0]:breek[ge:0]<verb><pres>[ge:0]
breek[ge:0][ge:1]:breek[ge:0]<verb><past>[ge:1]
gebreek[ge:1][ge:0]:breek[ge:1]<verb><pres>[ge:0]
gebreek[ge:1][ge:1]:breek[ge:1]<verb><past>[ge:1]

See also

• lttoolbox

Further reading

• Karttunen and Beesley (2002) "Finite State Morphology" (CLSI) ch. 8 "Flag diacritics"