From always, Xpath has matched all elements with a given query, and I had to add [1] at the end to match only the first match.
In OpenERP 7 I have this view definition:
<record id="view" model="ir.ui.view">
<field name="name">mail.message.full_expand</field>
<field name="model">mail.message</field>
<field name="inherit_id" ref="mail.view_message_form"/>
<field name="arch" type="xml">
<xpath expr="//field" position="attributes">
<attribute name="readonly">1</attribute>
</xpath>
</field>
</record>
Its purpose is to copy another view, but fully read-only. However it stops at the first match. Is there any way to make Xpath match every field?