What changes are not backwards compatible?

1. The removal of an event, object, attribute, data type, or enum member.
   1. The name of an event or object is missing in the NEW schema.
   2. The dictionary key of an attribute or data type (its implied name) is missing in the NEW schema.
   3. The dictionary key of an enum member (its value) is missing in the NEW schema.
   4. The uid or class_uid of an event is missing in the NEW schema.
2. Renaming an event, object, attribute, or enum member.
   1. A special case of removal in which the same caption belongs to an element with a different name, key, or class_uid; or the same class_uid belongs to an event with a different name.
3. Changing the data type of an attribute unless:
   1. The data type is changing from int to long. This exception is allowed on the basis that nearly all encodings use variable lengths by default, meaning that data written in nearly all encodings as an int can be safely interpreted as a long.
   2. Changing a scalar type when the underlying type (e.g. string_t) remains the same and there are no constraints on the new type.
4. Changing the requirement value of an attribute from optional or recommended to required.
5. Making the constraints of a data type more restrictive.
6. Adding a required attribute to an existing event or object.
7. Changing the caption of an event, enum member, or category.