[lextypes] DLL proof of concept

[Bob Foster]

What constitutes proof of concept for DLL (or anything like it)?

Here is a list off the top of my head:

- A reference implementation that accepts every valid definition and rejects
every invalid definition (that is defined as required to be reported,
according to the spec).

- An implementation that converts a valid definition to a form that allows
it to be used with one or more existing schema languages such that a value
is declared valid if and only if it conforms to the DLL definition.

- A language-independent API specification and an implementation in one or
more existing programming languages that allows, at a minimum, an
application to ask, for any string value, whether it is a valid instance of
a given datatype, and if so, to obtain the parse result. The API should be
able to operate independent of validation.

Bob Foster