Suppose the instance contains: 

   <person>
      <salary>
         <base xsi:type='xs:integer'>Hello<base>
         <bonus>Hello<bonus>
      <salary>
   <person>

And the relevant parts of the schema are: 

    <xs:element name="person">
     <xs:complexType>
      <xs:sequence>
          <xs:any processContents="skip" maxOccurs='unbounded'/>
      <xs:sequence>
     <xs:complexType>
    <xs:element>
    <xs:element name="bonus" type="xs:integer"/>

In this case, "salary" matches the wildcard with "skip". Now, it's clear 
that "salary" is not assessed and no validation outcome is computed for it. I 
have always assumed that this means no processing of the children of such an 
element (such as "base" and "bonus" above), even if we can find declarations 
for them. I think this is implied by the definition of "skip" in Section 3.10.1 
The Wildcard Schema Component [1], as well as the last note in section 5.2 
Assessing Schema-Validity[2]. Is there anywhere else in the Rec this is spelled 
out more explicitly? 

[1] http://www.w3.org/TR/xmlschema-1/#Wildcard_details 

[2] http://www.w3.org/TR/xmlschema-1/#validation_outcome