Good Auto-generation of POD from a Schema?

All,

Does anyone know of a tool that can create vanilla POD-like C++ structures from a Schema description?

Important qualities are:

• reasonable to use as "first class citizens" inside of the code.
• aggregates are packed just like native arrays.
• other, interactive language support ( i.e. Python or Matlab. )
  • use of each languages na开发者_如何学Gotive-types a plus.
• default and valid values defined and used.

Nice to haves are:

• no implicit use of the heap ( explicit through the schema would be okay )
• very light API ( no API is okay; element-name accessors-by-reference are okay; get_foo/set_foo is tolerable but discouraged. )

I've played with Google Protocol-Buffers briefly. It appears that a "repeated" & "packed" primitive satisfies one of my conditions, but the API is not designed for this use.

Context: I'm looking to write portable, high-performance code, ( thus must of my requirements, ) where intermediate products can be loaded / saved and then inspected and manipulated by proper analysis / scripting languages. The data structures are always changing, thus needing a way to auto-generate the classes for all languages involved.