OLE From an End User's Perspective

OLE lets users create compound documents by associating two types of data with an object: presentation data (which displays the object), and native data (which is all the information necessary to edit the object). Users can link or embed objects created in other applications into their files.

When users link objects into a file, they're really adding two things to the file: 1) the object's presentation data, and 2) a pointer to the object's source file (the file that created the object and which includes everything necessary to edit it). When someone updates the object's source file, the object in the document is updated as well. The tricky thing about working with linked files is that moving the source file from its original location, or moving the compound document to a location where it can't access the source, breaks the link.

When users embed objects in a file, they include both the object's presentation data and all the data necessary to edit it inside the compound document they're creating. This naturally makes files that contain embedded documents quite a bit larger. The following table compares linked versus embedded objects.

A Comparison of Linking and Embedding

Task	Linking	Embedding
Number of files	You have to maintain at least two documents: the source document for the linked object (such as a Microsoft Excel worksheet), and the destination document (such as a Word document) that uses the linked object. You can set the link so that changes in the source document reflect automatically in the destination document.	You have to maintain only a single file: the one that contains the embedded object.
Creating objects	Create a linked object by copying it from the source document and paste-linking it into the destination document.	Create an embedded object either by pasting or by dragging it and dropping it into the destination document.
Updating objects	More than one destination document can use the same source document. When you change the source document, all the destination documents are updated automatically.	You have to update the embedded object for each document in which its embedded.
Destination format	Depending on the nature of the object itself and the capabilities of the OLE client, you can link it in several different formats. For example, you can link worksheet data from Microsoft Excel into Word as an object that appears as a graphic, as formatted text, as unformatted text, as a picture, or as a bitmap.	All embedded objects appear as graphics in the destination document.
Maintaining objects	You have to keep track of separate files and maintain links between the source document and the destination document.	Everything you need is bundled with the file that contains the embedded object.
Object size	Because the source document exists as a separate file, the destination document isn't affected by the size of the source document.	Because the embedded object and all the information necessary to create it are stored in the destination document, that document can get quite large.
Managing objects	In some applications, you can use the Links command (usually on the Edit menu) to manage linked objects. For example, you can set a link so that you can update it manually or automatically, lock it, change it, or break it. You can relink data easily.	You can un-embed most embedded objects; they then exist as a picture. You can't re-embed them into their native format. To reduce the size of the destination document, save it under another name.