The current text in section 1 [1] does not clearly explain the meaning of this policy assertion  including this informational content [2] will help clarify the semantics of this policy assertion. 
  
Specifically, the first paragraph of section 1 [1] may be modified as follows:

This specification describes a domain-specific policy assertion for the SOAP Message Transmission Optimization Mechanism W3C Recommentation [MTOM] that can be specified within a policy alternative as defined in Web Services Policy 1.5 - Framework [WS-Policy]. This policy assertion indicates that messages are encoded as described in section 3 of the SOAP Message Transmission Optimization Mechanism [MTOM] using MIME multipart/related [RFC2387] and XML-binary Optimized Packaging [XOP]. For backwards compatibility, the policy assertion can also be used in conjunction with the SOAP 1.1 Binding for MTOM 1.0 [MTOMS11] Member Submission. 

[1] http://www.w3.org/TR/2007/WD-soap12-mtom-policy-20070918/
[2] Informational content: "This policy assertion indicates that messages are encoded as described in section 3 of the SOAP Message Transmission Optimization Mechanism [MTOM] using MIME multipart/related [RFC2387] and XML-binary Optimized Packaging [XOP]."