From looking at both a PC install of Kobo Desktop 2.02, and the zipped firmware 1.94 upgrade for a Kobo Touch it looks as if the dictionary is a series of files.
There is one binary file with an html extension for each pair of letters
Code:
28/05/2011 11:08 PM 2,027 aa.html
28/05/2011 11:08 PM 19,517 ab.html
28/05/2011 11:08 PM 34,131 ac.html
28/05/2011 11:08 PM 24,400 ad.html
28/05/2011 11:08 PM 6,675 ae.html
28/05/2011 11:08 PM 11,401 af.html
28/05/2011 11:08 PM 13,319 ag.html
28/05/2011 11:08 PM 1,324 ah.html
28/05/2011 11:08 PM 9,060 ai.html
28/05/2011 11:08 PM 331 aj.html
28/05/2011 11:08 PM 1,087 ak.html
28/05/2011 11:08 PM 36,961 al.html
28/05/2011 11:08 PM 24,794 am.html
28/05/2011 11:08 PM 54,143 an.html
28/05/2011 11:08 PM 845 ao.html
28/05/2011 11:08 PM 22,460 ap.html
28/05/2011 11:08 PM 2,070 aq.html
and then one large plain-text file that lists all the words
Code:
13/12/2010 10:21 AM 1,081,793 words
On the PC they are located in (assuming default locations) either
c:\Program Files\Kobo\dicthtml OR
c:\Program Files (x86)\Kobo\dicthtml.