Dynamic JSON schema modification

I have two folds of requirements :

1) building a JSON schema programmatically from a JSON

2) modify the schema if a JSON comes with new elements (this is a bit complex)

Here I must mention that the JSONs are having common skeleton structure. Only some may contain some more elements (attribute). So my program should first Build a schema according to the first JSON it gets and then should Read the next JSON and Identify the new elements in the JSON and Add the new elements to the Schema.

Can I get any help from the forum - any sample program?

Thanks.