Creating SOAP Error responses

I am creating a Web Service that internal client at my company will be calling. The service methods look like the following:

CreateProposalResponse ProposalSOAService::CreateProposal( CreateProposalRequest )

For the CreateProposalResponse message I need to add business Error Messages into the response. I've been reading a lot about putting errors into the SOAP Headers, but for business errors I don't feel that this is the appropriate place to put them because you this should be system/transport/validation kinds of errors not business Errors. Below is my response XML for the CreateProposal() SOA call. Can someone advice me on how to add Error messages to this response? I am having a hard time envisioning this and how the calling clients would determine the difference from a normal response and a business error/exception.

My CreateProposalResponse Message looks like the following:

<?xml version="1.0" encoding="UTF-8" ?>
<CreateProposalResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                       xsi:schemaLocation="http://xmlns.xxx.com/aces/proposal src/Proposal_v1.0.xsd"
                       xmlns="http://xmlns.raytheon.com/aces/proposal">
  <userId>022483</userId>
  <Proposal>
    <proposalTitle>SBT Prop</proposalTi开发者_高级运维tle>
    <proposalDescription>Proposal is for SBT</proposalDescription>
    <businessSegmentCode>SAS</businessSegmentCode>
    <proposalType>Test</proposalType>
    <proposalExternalRefID>SBT38829</proposalExternalRefID>
    <proposalStartDate>2009-01-01</proposalStartDate>
    <proposalEndDate>2025-01-01</proposalEndDate>
  </Proposal>
  <sourceSystemID>SBT</sourceSystemID>
  <targetSystemID>ACES</targetSystemID>
</CreateProposalResponse>

I agree with Aasmund Eldhuset unless these errors are an indication that the operation has failed. In that case, you should use a SOAP Fault.

How about simply having an <errors> array element as an optional element in your message, and populate it with one or more <error> elements describing the error(s)? Then, you could specify that a response message will either contain a populated <errors> element (along with other metadata elements that might be desirable even in the face of an error; perhaps <sourceSystemID> and <targetSystemID> are such elements?) but no <Proposal>, or it will not contain a <Proposal> but no <errors> (or the element will be empty).

(By the way, I agree that business errors should be indicated in the message body, not as SOAP errors.)