Robust Intra-document Locations

Several types of existing and next-generation hypertext functionality, including external hyperlinks, annotations, and transclusions, rely on references to locations within another resource. If the document domain cannot guarantee referential integrity, but rather is more like the World Wide Web, in which documents change regularly and without notification, potentially invalidating internal location references, it is crucial to build robustness into the intra-document location resolution mechanism, so that locations continue to function even as documents change chaotically. This paper aims to begin a process to evolve a standard for (normative) robust location descriptors and (non-normative) reattachment algorithms. We discuss criteria for evaluating the robustness of an intra-document location mechanism. Then we describe robust locations, an approach we believe meets these criteria. Robust locations include a standard minimal location descriptor and a recommended reattachment algorithm. We also suggest what can be done when the changes are so great that location resolution is problematic. Finally, we describe the implementation of robust locations within the Multivalent Document system.