Data transmission has three aspects: transmission, propagation, and reception.It can be broadly categorized as broadcasting, in which information is transmitted unidirectionally downstream, or telecommunications, with bidirectional upstream and downstream channels.
XML has been increasingly employed as a means of data interchange since the early 2000s, particularly for machine-oriented interactions such as those involved in web-oriented protocols such as SOAP, describing "data-in-transit rather than ... data-at-rest".
One of the challenges of such usage is converting data from relational databases into XML Document Object Model (DOM) structures.