<field name="relation_field" attrs="{'required': [('ttype','=','one2many')], 'readonly': [('ttype','!=','one2many')]}"/>
<field name="selection" attrs="{'required': [('ttype','in',['selection','reference'])], 'readonly': [('ttype','not in',['selection','reference'])]}"/>
<field name="size" attrs="{'required': [('ttype','in',['char','reference'])], 'readonly': [('ttype','not in',['char','reference'])]}"/>
<field name="relation_field" attrs="{'required': [('ttype','=','one2many')], 'readonly': [('ttype','!=','one2many')]}"/>
<field name="selection" attrs="{'required': [('ttype','in',['selection','reference'])], 'readonly': [('ttype','not in',['selection','reference'])]}"/>
<field name="size" attrs="{'required': [('ttype','in',['char','reference'])], 'readonly': [('ttype','not in',['char','reference'])]}"/>