Object linking and embedding -- COM

intro, components, standards, Java workgroup, corba and hush, summary, Q/A, literature

Reuse is not necessarily code sharing. In effect, there seems to be a trend towards sharing components at a higher level of granularity, as possibly independent applications. This approach has, for example, been taken by the Microsoft object linking and embedding facility (OLE), which offers support for embedding (a copy) of a component in a (container) component, for including a link to another component, and for storing compound objects. See slide 11-ole.

Object-enabling technology

OLE

document centered -- text, graphics, reports
component software -- standard programmatic interface
distributed object systems -- component object model
(D)COM

Features

linking, embedding, storage

Alternatives

IBM SOM/DSOM, Apple OpenDoc

slide: Object-enabling technology -- OLE

The OLE technology, which builds upon (D)COM technology, is characterized by its developers as object-enabling technology, to contrast it with a more classical language-dependent object-oriented approach relying on inheritance.

The object-linking technology allows the user to maintain a link from one application to another, so that for example a text processor may directly employ the results of a spreadsheet. Moreover, object linking is dynamic and allows any updates in the spreadsheet application to be reflected directly in the outcome of the text processor. In contrast, object embedding works more as the traditional cut and paste techniques in that it results in including only a copy of the material. To be embedded or linked, applications must satisfy a standard programmatic interface. In effect, the interface must provide the facility to request an update of the display of the information contained in the application. In this respect, the OLE technology may be characterized as document-centered.