Extensible Markup Language (XML)

Introduction The eXtensible Markup Language (XML) is a formatting language that allow the creation of text documents which are both computer- and human-interpretable. The standards for XML documents are created and maintained by the World Wide Web Consortium (W3C) [1], and describe the rules for marking data with tags. Similar to HTML, the use of tags allows the document creator to place additional meaning around data (whether numeric or text). In the case of XML, the tags are not pre-defined, so the document creator is free to select tag names that describe what the tag contains.

As an example, we will look at a simple XML document that shows a patient with some basic demographics:

  <Patient>
     <ID>1234567</ID>
     <Name>
        <Prefix>Mrs</Prefix>
        <First>Jane</First>
        <Last>Doe</Last>
        <Suffix/>
     </Name>
     <DOB>1/10/1970</DOB>
     <Gender>Female</Gender>
  </Patient>

In the above example, <Patient> is an example of a tag. You will notice that almost all of the tags come in pairs (i.e. <ID> </ID>), with the exception of <Suffix />. Because there is no suffix, this tag is empty. Empty tags can be displayed as <Suffix></Suffix> or <Suffix />. You will also notice that the tag names used are very descriptive of the data contained within, instead of providing information on how to format the text on the page (like HTML). This is because XML is meant to separate data from display, allowing it to be used instead as a flexible format for transporting information, as opposed to a static view of some data.

XML in Clinical Information Systems

(Article in progress)

• 1 - W3C XML [1]
• 2 - HL7 v3 Messaging Standards [2]
• 3 - Clinical Document Architecture (CDA) [3]
• 4 - Continuity of Care Record (CCR) [4]

Submitted by Luke Rasmussen