YaX is advertised as a key system, but it rather organizes
attributes in parameters, which parameters can be executed, so
that YaX is halfway between key management and macro definition
(and actually hopes to provide a user's interface). Values
assigned to attributes can be retrieved and tested in various
ways, with full expandability ensured as much as possible.
Finally, YaX's syntax is a quite peculiar (as few braces as
possible), but may be customized. YaX is based on texapi and
thus requires e-TeX.
