XML Dsig implementation ignores tag names and extra elements in SignedInfo. For example, the following XML passes validation:

...
<aSignedInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<aCanonicalizationMethod
Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"></aCanonicalizationMethod>

<aSignatureMethod
Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"></aSignatureMethod>

<aReference URI="">
<Transforms>
      <aTransform
Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"></aTransform>

</Transforms>
<aDigestMethod
Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"></aDigestMethod>
<aDigestValue>1Bq8FsjajUBYPD7stQeJSc66GlM=</aDigestValue>
    <test>some extra text</test>
</aReference>
</aSignedInfo>
<aSignatureValue>cbNpPGavhM0...</aSignatureValue>
...

Only Transforms tag is not affected.