Extensible Markup Language. A markup language that defines a set of rules for encoding documents in a format which is both human-readable and machine-readable.
Unlike HTML, XML’s set of rules is not chosen, but defined by its writer.
A properly written XML document has a ‘tree’ structure, in which each branch represents a data entity, starts with < and ends with >.
Here’s an example of XML representation for the DICOM Patient Identification Module:
<PatientIdentification>
<PatientName>Bond^James^Jr.^3rd^</PatientName>
<PatientID>007</PatientID>
<PatientBirthDate>19440709</PatientBirthDate>
<PatientSex>Alpha Male</PatientSex>
</PatientIdentification>
XML’s use has expanded as a result of increasing popularity of web services.
Because XML is stripped from all but its own text, it is readable to all applications and hardware, which allows software developers to sort, store, and transport data in various applications and web pages.
One of the major arguments against XML is that it takes a lot of memory and disk space because the data element names tend to be larger than the data itself.
Example:
HRZ’s HL7Kit can convert messages received using the HL7 standard to XML and send them to a 3rd party application for processing. XML popularity has made it the de-facto standard for data exchange between web applications.