!~~prefixedDec
        corresponding strings in documents must begin with the
        associated string in the schema, and the right part of strings
        in documents must be decimal.

def prefixedDec(nstr, schema):
    """
    !~~prefixedDec
        corresponding strings in documents must begin with the
        associated string in the schema, and the right part of strings
        in documents must be decimal.
    """
    if not nstr.startswith(schema):
        return False
    postfix = nstr[len(schema):]
    try:
        int(postfix)
    except ValueError:
        return False
    return True