title: Creating own XSD schema
body: <p>I have wrote program for xml signing. I added some <strong>HashDataInfo</strong> elements which are described in <a href="https://www.w3.org/TR/XAdES/" rel="nofollow noreferrer">https://www.w3.org/TR/XAdES/</a>,but there is no description for them in <a href="https://uri.etsi.org/01903/v1.3.2/XAdES.xsd" rel="nofollow noreferrer">https://uri.etsi.org/01903/v1.3.2/XAdES.xsd</a> , so when I am validating xml document against that schema, it shows exception (Invalid <strong>HashDataInfo</strong> element).
  I have added in XAdES.xsd schema description for HashDataInfo,and now everything is good.
  My question is.
  Is it legal or not? Can I have some problems in future? Or I just can edit xml schemas and there will be no problems with standard?</p>