Quaker,

I don't think the reference to META file types is appropriate in this case.

Xara's *.XAR and Adobe Photoshop's *.PSD files would more correctly be termed PROPRIETORY file types. They contain information (vector, bitmap, etc.) in standard or non-standard forms plus their own, propietory information used to implement their specific features, methods, attributes, protections, etc.

META, as used in high tech, is almost always used as Merriam-Webster's dictionary specifies in #3 below:

"META
Main Entry: meta-
Variant(s): or met-
Function: prefix
Etymology: New Latin & Medieval Latin, from Latin or Greek; Latin, from Greek, among, with, after, from meta among, with, after; akin to Old English mid, mith with, Old High German mit
1 a : occurring later than or in succession to : after <metestrus> b : situated behind or beyond <metencephalon> <metacarpus> c : later or more highly organized or specialized form of <metaxylem>
2 : change : transformation
3 [metaphysics] : more comprehensive : transcending <metapsychology> -- used with the name of a discipline to designate a new but related discipline designed to deal critically with the original one <metamathematics>
4 a : involving substitution at or characterized by two positions in the benzene ring that are separated by one carbon atom <meta-xylene> b : derived from by loss of water <metaphosphoric acid>".

For example, HTML META tags contain descriptions of the HTML tag contents in the file. SGML and XML are METALANGUAGES used to define other languages. BNF (Backus-Naur Form) is a META language used to describe other languages (programming languages like C++ are formally described in BNF).

Please pardon my running on.