In this case,if you write some stirng in your fields which contains '<' , OpenERP will give a error:
Unescaped '<' not allowed in attributes values
you can use '<' instead it.
for more infomation(like why does '>' work properly ) considering this:
http://stackoverflow.com/questions/6322126/whats-the-big-deal-with-using-the-lt-instead-of-simply-to-do-comparison