One of the fundamental ideas behind COM is that of binary compatibility. According to Microsoft, a client written in any language can use a COM component. This is sort of true. What is left to discover is that some client environments require more "support" from the component. Clients fall into roughly 2 camps of unequal capability. The first camp is exemplified by languages like C++, and (later by) VB. These languages are perfectly aware of QueryInterface (QI) and can generally access any interface supported by a component through the v-table, or custom portion of a dual interface.
