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

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"