DDSXTY — Improve support for shared data

The Type System currently allows a type designer to specify that the storage for a type member may be located outside of the type itself. (This is an important capability when, for example, objects of the member’s type are very large.) However, it provides insufficient flexibility when such objects are stored in collections: the entire collection may be stored externally, but the collection members must be stored contiguously.
Resolution:
Enhance the Type System to allow collection elements to be shared, not just members of aggregation types. In the IDL Type Representation, this shall be expressed syntactically by the application of the built-in @Shared annotation to the collection member type.

Enhance the Type System to allow collection elements to be shared, not just members of aggregation types. In the IDL Type Representation, this shall be expressed syntactically by the application of the built-in @Shared annotation to the collection member type.
Note that this resolution does not provide a general-purpose annotation facility for collection members. It merely provides an appropriate Type System property and Type Representation syntax to express it.
Sequences:
sequence<@Shared Foo, 42> sequence_of_foo;
// or:
sequence<
Foo, //@Shared
42
> sequence_of_foo;
Arrays:
Foo array_of_foo @Shared [42];
// or:
Foo array_of_foo //@Shared
[42];
Maps:
map<string, @Shared Foo, 42> map_of_string_to_foo;
// or:
map<
string,
Foo, //@Shared
42
> map_of_string_to_foo;
Strings: Strings will not support this feature (i.e. individual characters cannot be stored externally to the string itself). Since string elements can only be individual narrow or wide characters, this “limitation” in theory is not expected to be a limitation in practice.