What Does Plain Old XML (POX) Mean?
The term "plain old XML" (POX) is a reference to certain types or uses of the eXtensible Markup Language (XML) that are less complex or sophisticated than other versions of the language. In general, POX refers to the simple ways of using XML in projects.
Techopedia Explains Plain Old XML (POX)
One of the more technical definitions of POX is that it is an unadorned XML that is transferred over simple protocols such as HTTP, SMTP or FTP, or through some kind of proprietary middleware product. POX can also be defined technically as a type of XML that is unencumbered by wrappers such as SOAP.
IT Professionals may also use POX in a slightly different context. There is the issue of whether to create a schema or additional documentation for XML code models. The idea is that, although there are situations where schemas and other resources may be necessary for larger projects where many pairs of eyes will be on the XML code, there are other situations that can work well without these kinds of extras.