Unlike link, the semantics of olink are application specific. The olink element provides a mechanism for establishing links across documents, where ID/IDREF linking is not possible and URI-based linking may be inappropriate.

In general terms, the strategy employed by olink is to point to the target document by URI, and point into that document in some application-specific way.

Other elements can also behave like olink by using the common linking attributes xlink:href and xlink:role. When an element has an xlink:role="http://docbook.org/xlink/role/olink" attribute, then its xlink:href attribute is interpreted using olink semantics. That is, the part of xlink:href before the fragment identifier (#) is interpreted as equivalent to an olink targetdoc attribute value instead of a URI, and the part after the fragment identifier as an olink targetptr attribute value.

anchor, link, xref