Assign value to claim through ClaimsTransformation

What is the recommended way to simply assign a default value to a claim through ClaimsTransformations?

For instance:

  // Validation failed: The 'DefaultValue' attribute is not declared.Schema validation error 

  <!-- Assign the true to 'extension_isProfileComplete' claim whenever users fill in all required info at signup -->
       <ClaimsTransformation Id="ProfileIsCompleted" TransformationMethod="CopyClaim">
        <InputClaims>
          <InputClaim ClaimTypeReferenceId="extension_isProfileComplete" TransformationClaimType="inputClaim"/>
        </InputClaims>
        <OutputClaims>
          <OutputClaim ClaimTypeReferenceId="extension_isProfileComplete" DefaultValue="true" AlwaysUseDefaultValue="true" TransformationClaimType="outputClaim"/>
        </OutputClaims>
      </ClaimsTransformation>  

I know I can achieve the same using a TechnicalProfile only for that but it seems overkill.

Solution 1:

I use:

    <ClaimsTransformation Id="CreateXXX" TransformationMethod="CreateStringClaim">
        <InputParameters>
            <InputParameter Id="value" DataType="string" Value="Some value"/>
        </InputParameters>
        <OutputClaims>
            <OutputClaim ClaimTypeReferenceId="xxx" TransformationClaimType="createdClaim"/>
        </OutputClaims>
    </ClaimsTransformation>