Looking for existing schema

[Steve]

Hi,

I'm trying to find out if a particular schema I've been asked to develop
already exists.

The schema itself will hopefully represent the definition of messages on a
1553 Milbus. For example - I'll need to define data elements and their bit
positions, sizes, fixed point scaling factors, frame rates for messages,
etc.

Is there such thing as central repository of public schemas? Or can someone
suggest useful sites where I can search for existing schemas? Or better
still, a schema already complete to save me some work!

Thanks for any help.