Objectives: The WG must identify and define the necessary elements and the technical procedures for the digital signature of XML documents and for the management of style sheets on a national basis.
Reasons: The motivation for the creation of this WG is that the documents in HL7 CDA Rel. 2.0 format are based on the XML language and, considering the different types of signature available today, the identification of a homogeneous way of signing for all the Regions, would simplify not only the digital subscription process, but also that of verifying the signature. In addition, the need to standardize the display of the contents of clinical documents in HL7 CDA Rel. 2.0 format requires the identification and definition of a minimum set of style sheets shared on a national basis.
Context and experiences: European and Italian standards provide for three types of digital subscription, identified by the acronyms CAdES, PAdES and XAdES. The CAdES subscription allows you to sign any type of document, the XAdES subscription only XML documents, and finally the PAdES subscription only PDF documents. In particular, XAdES provides for different types of signature, such as enveloped, enveloping and detached. As far as style sheets are concerned, their use (necessary to render documents in HL7 CDA Rel. 2.0 format) poses problems relating to the signature’s verification of documents in HL7 CDA Rel. 2.0 format themselves, since, on the basis of the specific style sheet, the data presented to the signer do not always coincide with all those contained in a document. The criticality is represented by the need to guarantee the signatory the repudiation of any data not presented at the time of signature and the non-repudiation of those present. HL7 International has defined a generic style sheet, which has been made available on the web portal of the Electronic Health Record, in the section dedicated to the collection of style sheets on a national basis (http://www.fascicolosanitario.gov.it/fogli-stile).