an ASCII text file with XML markup tags
an old fashioned flat text file (which contains the data) which also references another flat text file (called a schema) which contains the structure of that data
a plain text file, so you could easily create and edit the file using Notepad
a simple text file--just like HTML, but unlike a WordPerfect or DBase file, for example
a simple text file, which can be transferred across the Internet just like HTML
a text file you can edit with any editor like WordPad
a well structured, plain text file