There are several rules and a catch-matching priority scheme for executing a
<catch>.
For details, see
Rules for Catching Faults in a Catch Activity
.
If fault cannot be matched to a
<catch>
using the rules referenced above, then it executes the
<catchAll>
.
If there is no
<catchAll>
within the fault handlers, then the implicit fault handling logic executes. This logic acts like there is a
<catchAll>
present that contains a single compensate activity that executes the default compensation routine for all enclosed scopes. Once executed, the original fault is rethrown to the next enclosing scope or the process if none is available. If the handler is already at the process level, then the process terminates with the fault.

<faultHandlers>
 <!-- catch all faults with a matching name, but no data -->
  <catch faultName="x:foo"> 
    <empty/>
  </catch>
 <!-- catch all faults with the matching variable type,
       whose name is not "x:foo"-->
  <catch faultVariable="bar"
    faultMessageType="tns:barType>
    <empty/>
  </catch>
 <!-- catch the fault specified by the name 
        and variable type -->
  <catch faultName="x:foo" faultVariable="bar"
     faultMessageType="tns:barType>
    <empty/>
  </catch>
<!-- catch all faults not caught by a specific handler -->
  <catchAll>
    <empty/>
  </catchAll>
</faultHandlers>