Day & Zondervan's Mobile Access Position Paper

Some Lessons Learned from Mobile Access

55 Cambridge Parkway, Cambridge, MA 02142, USA

Lotus has been shipping products supporting mobile access to shared information for longer than the Web has existed. We briefly outline the nature of those products, the likely impact of new technology, and what we think W3C should learn from what Lotus has done.

Lotus Products for Mobile Access

Lotus Notes was first described in the open literature in 1988 [Kawell 88]. Although it has undergone a tremendous number of improvements since then, including the server's transformation into the Lotus Domino web server, the core concepts of that paper are still present in today's shipping product:

weak network connectivity (rarely-connected networks) leads to a need for local replicas of a shared database.
in a rarely-connected network, serializable updates to shared information are very expensive.
group communication applications (now called groupware) need not implement serializable updates to shared information; weaker consistency is acceptable
a very robust system can be built by treating all replicas equally (no master copy).
replication must be a background activity that can take place while the user is performing other actions.

Other Lotus products are also worth noting for this workshop: Lotus Weblicator uses Notes technology to cache web sites and Notes databases for offline use. Lotus EasySync synchronizes PalmPilots with Notes email, calendar and address book. The Domino Pager Gateway allows Notes users to send pages to each other, and to have content automatically forwarded to their pagers (currently limited to one-way alpha-numeric pagers). Domino Wireless Access allows users to access their Notes email, calendar and address book from a cellular telephone, using Unwired Planet's HDML technology.

Research Projects

In the Lotus research group, we are currently exploring the use of 2-way pagers such as the Motorola PageWriter 2000. These have very small, character-cell screens; barely usable keyboards; and unpredictable delivery times for communication between the pager and Notes. We run simple agents in Notes to forward email to the pager and to rewrite email coming from the pager. Despite the many limitations of these devices, no-one who has one of these will give it up. Wearing the device changes one's relationship to email in interesting ways. We anticipate that we will extend our experiments to include address-book and calendar functionality.

Lessons Learned

Replication technology is vital for disconnected access, and we believe that mobile access is synonymous with weakly-connected access. The Web model of permanent connection may be reasonable when dealing with desktop machines on Ethernets, but is suspect when dealing with two-way pagers in tunnels.

We are enthusiastic about open protocols and standards. Nevertheless, it is worth noting that modern Notes replication is much faster than the algorithm described in [Kawell 88]. The details of the replication technology have changed several times since the initial release as we have learned new ways to organize information for more efficient replication. We would caution against fixing a standard too early. We would also caution against casually adding replication to HTTP.

Notes replication works better than replication on the Web partly because the default unit of replication is a database, which is larger than a document but smaller than a site. Both for replication and for printing, it will be useful to add annotations (possibly in RDF) describing the structure of collections.

For wireless access, we would like to see standardization based on HTTP and XML. Unfortunately, HDML is rapidly becoming the de facto industry standard, and we would strongly encourage working with Unwired Planet to bring HDML under the XML umbrella.

References

[Kawell 88] Leonard Kawell Jr., Steven Beckhardt, Timothy Halvorsen, Raymond Ozzie, and Irene Greif. Replicated Document Management in a Group Communication System. Proceedings of the Second Conference on Computer-Supported Cooperative Work (CSCW), 1988. Reprinted in David Marca and Geoffrey Bock (eds.), Groupware: Software for Computer-Supported Cooperative Work. IEEE Computer Society Press, 1992.