2.3 Component taxonomy

Conceptually, Office documents may have up to three classes of components: images, OLE-based embedded components, and virtual components. Images are graphic data that are stored and manipulated directly by the application. This includes the cached versions of any embedded components and any graphic data that the application manipulates directly. OLE-based embedded components are data created using a separate application, as described above. Among the most common types of embedded components are components that implement image types. To differentiate these image types (which are created by a separate application, and hence a type of component) from the primitive images managed by the application we will use the term ``image components.'' Finally, virtual components are objects that are not implemented as OLE-based components but that are perceived by the user as separate entities (i.e., pages in Word, slides in PowerPoint, and sheets in Excel).