CORBA35 — Section: Chapter 9, Chapter 5

Section 9.2.9 says "A reference to a DynValueCommon interface (and interfaces derived from it) exhibit the same sharing semantics as the underlying valuetype that it represents.", which defines the sharing semantics of DynAny. However, I think its precondition is that valuetype's sharing semantics can be preserved in Any. DynAny is usually used with Any, converted from or to Any. If Any can't preserve sharing semantics, there is no necessary for DynAny to keep them. Suppose we use a struct which consists of several valuetypes to store a graph. In order to ensure the correctness of an application based on DII/DSI, converting this struct to Any and then to DynAny should produce an identical graph. However, if Any can't preserve sharing semantics, this goal is impossible. Any's sharing semantics focuses on valuetype conversion, because we don't concern the concrete internal implementation of Any. It means that when we extracting valuetypes from an Any or converting an Any contains valuetypes into a DynAny, sharing semantics should be preserved. For example, different Anys contain same valuetype only produce one valuetype instance when their contents are extracted. We can implement this by the help of a global valuetype manager. To sum up, the sharing semantics of valuetype can be divided into three layers: valuetype itself, Any and DynAny. All of them constitute a complete hierarchy. Only after each layer has been implemented, we are able to ensure that applications that use the DII and DSI can correctly view and preserve the semantics of the valuetype graph. Because Any's sharing semantics is very fundamental, it is necessary for us to clarify it in the specification, though we haven't special chapter/section on Any. We can add it to Chapter 5 "Value Type Semantics". Section 5.2.4.2 only defined sharing semantics in the layer of valuetype itself. We should say something about sharing semantics in the other two layers at the end of this section.