Grouping an XPath function reference within an arbitrary set of elements

I have XML such as

<doc>
 <Object id="x">
  <Attributes>
   <MATERIAL>PLA</MATERIAL>
   <METHOD>Inserted</METHOD>
   <PRESSURE>HP</PRESSURE>
  </Attributes>
 </Object>
 <Object id="y">
  <Attributes>
   <MATERIAL>P</MATERIAL>
   <METHOD>Unknown</METHOD>
   <PRESSURE>HP</PRESSURE>
  </Attributes>
 </Object>
 .
 .
 .
</doc>

where the Object element appears an a priori unknown number of times, and I want to have an XPath expression that returns a 0 or 1, if a condition holds true within any (at least 1) of the Objects.

Doing something like

number(boolean(//Object/Attributes[(MATERIAL="PLA")])) * number(boolean(//Object/Attributes[(METHOD="Unknown")])) 

returns 1 because both are true somewhere, but I want a 0 because nowhere within any single Object are they both true.

I am restricted to XML 1.0.

I was hoping for a slick solution perhaps involving some kind of predicate on Object that I have not been able to discover.

Each Object attribute is unique, if that can be leveraged.

Drawing on a parallel to SQL, I want to somehow group by the Object when applying the condition of interest.

While I can programmatically extract the Objects and process them individually, I would really rather not!

TIA, Dave