Zippering : Managing Intermittent Connectivity in DIANA Arthur

ion-Control (PAC) model [3] and the Serpent model [1] have some overlap with the DIANA model in that they all attempt to separate the presentation of a user interaction from its functionality within the application logic. DIANA proposes a form-based solution to implementing a user interface architecture in which the core application logic is de-coupled from the interface logic. The applications in DIANA use a form based approach in which applications do not have to be responsible for ne-grained rendering details as user's input or retrieve information to and from the forms. The fact that existing interfaces require most applications to control the presentation on a very interactive and ne scale is regarded as one of the reasons why human computer interfaces are hard to design and implement [11]. Imielinski and Badrinath [8] identify some of the issues involved in mobile wireless computing, including location management, con guration management, disconnection, cache-consistency, recovery, scale, e ciency, security and integrity. The paper also presents a model of a system to support Mobility. In this system, Mobile Units are assumed to have wireless e-mail access to Mobile Support Stations ( xed network hosts with a wireless e-mail interface to communicate with the mobile units). Most of our discussion assumes the presence of a similar system for the purposes of wireless e-mail communication. The Coda File System [15] is a highly available le system designed to suit distributed and mobile computing. It uses an optimistic replica control strategy to provide high availability and relies on a dynamic cache manager to provide disconnected operation. DIANA proposes to use a similar caching strategy to minimize the network utilization and improve e ciency in addition to support disconnected operation. Details of various aspects of the Coda File System are available in [13, 14, 16]. Java [7] is a language for portable applications that may be disseminated among a variety of platforms. HotJava is a browser that allows dynamic fetch of Java applets over the Internet in a manner that extends the notion of the World Wide Web. HotJava works best in a connected network environment; it has no special features to handle disconnected or intermittently connection operation. 1.3 Outline of Paper In this paper, we describe the architecture and show the bene ts of using the DIANA architecture in mobile computing. Section 2 describes an application example using the DIANA architecture. Section 3 gives an overview of the DIANA architecture. Section 4 shows the connected operation. Section 5 focuses on disconnected mode. Section 6 illustrates the design issues for Application Surrogates. Section 7 describes current state of the DIANA architecture. Section 8 discusses future issues about versatile connectivity. We conclude with section 9. Keller, Densmore, Huang, and Razavi / Zippering in Diana 5