3.1 Object Replacement Character, U+FFFC

Short description: The object replacement character is used to stand in place of an object (e.g. an image) included in a text.

Reason for inclusion: The object replacement character was included in Unicode only in order to reserve a codepoint for a very frequent application-internal use. Many text-processing applications store the text and the associated markup (or in some cases styling information) of a document in separate structures. The actual text is kept in a single linear structure; additional information is kept separately with pointers to the appropriate text positions. The overall implementation makes sure that these two structures are kept in sync. If the text contains objects such as images, it is extremely helpful for implementations to have a sentinel in the text itself; any additional information is kept separately.

Problems when used in markup: Including an object replacement character in markup text does not work because the additional information (what object to include,...) is not available.

Problems with other uses: The object replacement character is also problematic when used in plain text.

Replacement markup: The markup to be used in place of the Object Replacement Character depends on the object in question and the markup context it is used in. Typical cases are <html:img src'...' />, <html:object ...>, or <html:applet ...>. These constructs allow to provide all additional information needed to identify and use the object in question.

What to do if detected: In a proxy context or browser context, ignore. When received in an editing context, remove, maybe with a warning to the user.