Generalized Annotations for Shared Commenting, Content Rating, and Other Collaborative Usages

Martin Roscheisen, Stanford University
Terry Winograd, Stanford University

ComMentor implements a generalized form of inline annotations to arbitrary documents on the Web. Based on which "annotation sets" a user has chosen, annotations from these sets are retrieved from a third-party server. A rich number of usages can be realized with this architecture, including seals of approval/content rating, structured discussion about paper drafts, collaborative filtering, tours, shared "hotlists" with section-based visibility control, usage indicators, co-presence, and value-added trails. We have defined and implemented a general object request protocol for requesting and managing annotations on third-party servers. We are looking into the kinds of extensions to HTML and http we are suggesting based on the lessons learnt from the prototype implementation and our subsequent experience with using it.


Martin Roscheisen, Christian Mogensen, and Terry Winograd (1995).
ComMentor Home Page. URL:

Annotations as Third-party Value-added Information

There are many different reasons why people want to communicate to each other about specific things they find as networked information resources. These include comments and annotations of the kind a workgroup would share about their common area of interest, the ability to have newsgroup-like fora associated with specific items on the "net", value-added trails that link items together that someone considers being connected under a particular view, systematic critique and review information, "Seals of Approval" (SOAPs)/content ratings, or filters in support of enabling people to make sense of whatever information is presented to them, as well as usage indicators (such as how often a particular documents has been looked at by a group of people), "hotlists" generalized to shared structures which look different depending on who (with which access rights) look at them, or filters in support of enabling people to make sense of whatever information is presented to them.

All of these applications have in common two properties that are not associated with the standard mechanisms for hypertext (http, HTML):

For example, consider a set of "consumer reports" annotations provided by a review organization and attached to product catalogs on the web, or the private (within the group) comments made by our local research group as part of their joint reading of the WWW conference proceedings. In each case, the annotations themselves need to be kept separate from the annotated documents and access to them handled in a uniform way for appropriate subscribers.

We have argued that the legal, social, and economic independence of third-party value-added information needs to be reflected architecturally in the technical framework.

We designed and developed a general mechanism for such third-party value-added information, prototyped in the "ComMentor" system. It enables people to share annotations to arbitrary documents at any position in-place, share comments/pointers with other people (either publicly or privately), and create shared "landmark" reference points in the information space. The framework also represents a further step towards giving people a presence on the Web, laying the foundation for on-line communities.

The idea of a system enabling a multiplicity of independent individuals to create lightweight value-added "trails" through a document space was envisaged most prominently by Vannevar Bush as early as 1945 [BUSH]. ComMentor can be thought of as a tool which such "trail blazers" use to add value to contents, and which other people use to find guidance based on these human-created super-structures. The overall architecture can be seen as a platform where value-added providers can provide their services (as a third player next to content providers and end users).

There are a number of existing systems that incorporate mechanisms that are related to our current architecture. These include the annotations facility in Lotus Notes (which requires making available "hooks" for annotation attachment in a given document), annotations in Acrobat (which are in-place but not shared), and various other in-place facilities which are based on a shared file system to allow multiple people to share comments (these include ForComment(TM), and some versions of MS Word--both of which are not incremental, that is, only one user can write comments at a given time, and then pass on this right.)

In the World-Wide Web arena, there has been ongoing discussion about the appropriate mechanisms for group annotations, but these have generally assumed whole-document attachment (rather than attachment in place) and universal (rather than access-controlled) distribution. They have not been developed into widely used facilities. There are a few experimental systems dealing with annotations of various kinds. Ubique uses a proprietary architecture, geared towards synchronous user-user communication rather than value-added structures.

We describe the overall ComMentor architecture including a description of the user view and a note on how documents are synthesized. We then discuss our experience using the facility and describe a variety of usage scenarios that we are currently aware of.

Much of the technical detail is specified in our publications, including the implemented version of the client-server protocol and the definitions of the meta-information objects relevant for implementing shared comments to distributed documents. A second-cut version of this protocol based on lessons learnt in the first cut might be a good candidate for standardization.