The use of XML was mandated by the e-Government Interoperability Framework (e-GIF) programme as the standard to be used for messaging by government organisations and accordingly this has been adopted by the NHS.
For the most part, the schema applies the data specifications as authorised by the NHS and documented in the NHS Data Model and Dictionary.
The Issued Documentation
NHS Data Standards maintain and issue the following schema documentation:
- The Schema Files (generated using ALTOVA XMLSPY ©)
The Schema files consist of a series of interpretable XML/HTML statements which define the data structures and content rules for the use of the message. User systems use the schema to either populate or interpret a 'schema instance' that is the resultant XML formatted message file which carries the data.
The schema therefore represents the 'design' of the message and it may be necessary therefore to interpret and understand the information inherent in the schema file code.
- The Schema Documentation (generated using ALTOVA XMLSPY ©)
These files are generated using XMLSPY software and may be read in any browser, e.g. MS Explorer©. The files consist of a 'root' entry HTML formatted file and a (usually) large number of supporting .png graphic files used by the root HTML.
This documentation enables useful "drill down" functions for investigating structures and data items, but these features are not as powerful as when using a full schema editor (see below).
Most browsers will support printing and thus the schema details can be printed as required but users are warned that browser based prints often generate a large number of pages.
The CDS-XML schema generates approximately 450+ pages of details, printing is therefore not advised.
- The Schema Release Note
This is a text based MS WORD document identifying the changes applied to the schema release.
References to Information Standards Notices and other technical change requirements are detailed.
Whilst schema can be read as HTML in most browsers, it may be difficult to fully interpret the schema unless the reader has a detailed understanding of HTML.
It is recommended that schema are read using an XML interpreter (such as ALTOVA XMLSPY ©), many of these are freely available on the internet.
Schema technicians may prefer to use such software to examine schema more deeply as the interactive facilities provided are generally more powerful than browsing the XML/HTML supplied schema code.