schema.xml question

[Antonello Mangone]

Hello everyone, my question is ....
Is it possible in schema.xml set a group of fields to use as a default field
to query in "OR" or  in "AND" ???

example:

<group name="group_name">
    <field name="a" type="..... />
    <field name="b" type="..... />
    <field name="c" type="..... />
</group>

<defaultSearchField>group_name</defaultSearchField>

Thanks in advance