4.3 Terminology

To avoid misunderstandings, here we'll supply the meaning we give to some terms used in this chapter. We don't provide formal definitions: we just want to ease the understanding of some concepts. To better understand these concepts, see COM's documentation.

Component

a piece of software with some functionality that can be used by other components. It's composed by a set of objects that implement this functionality.

Component Object

an object through which all the functionality of a component can be accessed, including its other objects. This object may have many interfaces.

Application Object

A component object with a interface that comprises all the top-level functionality of a component; the client does not need to use other interfaces of the component object. This concept simplifies the understanding of a component, as it puts all its functionalities in an hierarchical manner (an application object together with its sub-objects, which can only be accessed through methods and properties of the application object).

COM server

Some piece of code that implements one or more component objects. A COM server must tell the other applications and components which component objects it makes available. It does so exposing them.

OLE control

An object that has an user interface, and can be embedded inside other applications that have OLE containers (usually C++ or VB applications).

CoClass

A type library describing a component should have a CoClass entry, specifying some information about the component:

• a name, differentiating one CoClass from others in the same type library;
• its CLSID, the unique identifier that distinguishes this component from all others;
• the interfaces of the component object, telling which one is the default. In a typical situation, only one interface will be supplied; thus the component object could be called an Application object for that component;
• the source interface, that is, the interface the component uses to send events to the client. This interface is not implemented by the component: it just uses objects that implement this interface.

Lua Application Object

It's the Lua table used to implement the Application Object.