Owen M. Densmore

Zippering: managing intermittent connectivity in DIANA

This paper describes an approach for handling intermittent connectivity between mobile clients and network‐resident applications, which we call zippering. When the client connects with the application, communication between the client and the application is synchronous. When the client intermittently connects with the application, communication becomes asynchronous. The DIANA (Device‐Independent, Asynchronous Network Access) approach allows the client to perform a variety of operations while disconnected. Finally, when the client reconnects with the application, the operations performed independently on the client are replayed to the application in the order they were originally done. Zippering allows the user at the client to fix errors detected during reconciliation and continues the transaction gracefully instead of aborting the whole transaction when errors are detected.

The Diana Approach to Mobile Computing

DIANA (Device-Independent, Asynchronous Network Access) is a new application architecture to solve two major difficulties in developing software for mobile computing—diversity of user interface and varied communication patterns. Our architecture achieves display and network independence by de-coupling the user interface logic and communication logic from the processing logic of each application. Such separation allows applications to operate in the workplace as well as in a mobile environment in which multiple display devices are used and communication can be synchronous or asynchronous. Operation during disconnection is also supported.

A user-interface toolkit in object-oriented PostScript

Only the diehards want to develop applications using basic window system facilities. The preferred approach is a higher‐level “toolkit” of user interface components, such as menus and scroll bars. Experience with current toolkits shows the need for an object‐oriented interface to these components.