It's nice to see SQLite supports table constraints:

$ sqlite3 test.db
SQLite version 3.6.19
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> create table t1
   ...> (k int,
   ...>  s int,
   ...>  e int,
   ...>  d int,
   ...>  constraint se_or_duration check
   ...>    ((s is not null and e is not null) or d is not null));
sqlite> insert into t1 values (1, 8, 4, null);
sqlite> insert into t1 values (2, null, null, 8);
sqlite> insert into t1 values (3, null, null, null);
SQL error: constraint failed
sqlite>

It's been a while since I've looked at Factor, and things are looking good.

When using emacs with Factor under Microsoft Windows, remember to make sure before you start Factor that emacsclient is in your path, and then do:

"editors.emacs" require

to tell Factor your going to use emacs. After that, make sure that you've started the server in emacs with server-start and try something like:

\ . edit

to see the definition of the . word.