Mobile Database Design, Access, & Transactions ❯ UbiData: Ubiquitous Data Access

Overview

In today's networked computing environment, users demand constant availability of data and information which is typically stored on their workstations, corporate file servers, and other external sources such as the WWW. An increasing population of mobile users is demanding the same when only limited network bandwidth is available, or even when network access is not available. Moreover, given the growing popularity of portables and personal digital assistants (PDA), mobile users are requiring access to the data regardless of the form-factor or rendering capabilities of the mobile device they choose to use. The UbiData Project, currently funded by the National Science Foundation, addresses the challenges and new requirements imposed by mobility. In particular, UbiData aims to provide algorithms, protocols, and system implementations that enable:

• Any time, any where access to data, regardless of whether the user is disconnected, weakly connected via high-latency, low-bandwidth networks, or completely disconnected.

• Device independent access to data, which allows users to switch among different portables and PDAs, even while mobile.

• Support for access and modification of data within classes of related applications, which do not utilize common formats, for example using an ASCII text editor to modify a MS Word document.

UbiData is based on a three-tier architecture that supports the automatic hoarding of data from multiple, heterogeneous sources into a variety of mobile devices with different characteristics. The middle tier eliminates the manual and tedious synchronization currently done by the user, between the mobile device and the fixed network on the one hand, and between multiple mobile devices owned by the user on the other hand. This middleware enables the automation of synchronization tasks in both connected mode (following disconnection) and weakly connected mode, where only intelligent and effective synchronization can be used in the presence of a low-bandwidth network.

Application independent document editing for mobile devices

The motivation for this work is to allow a use case where a person could take a StarOffice/MS Word document, convert it to text and transfer it to a low capability mobile device over a possibly low bandwidth connection and merge the changes from the edited document back into the original document with no effort. Apart from convenience, a text document is on average 80% smaller than the original word document (based on data gathered from 398 random word documents) so the bandwidth savings are enormous. Most research on bandwidth adaptation has not considered this possibility except the OpenOffice XMerge group. The XMerge group is using a plugin based system to allow for document conversion and merge. Although, document conversion to text and imposition of a basic document structure on text is application/format specific, it should be possible to implement a generic diff/patch or merge procedure. This is what we are trying to explore and are using a diff/patch methodology to allow for version control. The generic diff/patch system also implies the possibility of using any editor to edit the text document and then merge the changes back to original document which would make the editing system application independent. This capability is a step towards meeting the goals of the ubidata project viz. ubiquitous data access, inspite of device, network and application limitiations. The system is being implemented by adding to and modifying existing code written by the INRIA VERSO group, Rocquencourt, France. We use XML as an intermediate format to allow a generic diff/merge system to be devloped. The INRIA VERSO groups XyDiff tool allows for computing the diff betweeen two XML documents and patching diffs onto the original document. However in this domain, when the edited text is used, all formatting information has been lost and we need to reconstruct the edited documents hierarchical structure from the information contained in the original document before we can apply the diff/merge. Hence the diff procedure is being modified and the patch procedure is maintained as is. Initial results using Abiword as a source editor have been favorable. The code is intended to be GPLed and available for comments and free download after additional work and testing is completed.

Objective

The overall self describing sensor network approach is based on the need to provide a scalable, plug and play, smart sensor network that is more flexible and maintainable. The approach leverages both mature and new technologies and standards to develop the system architecture composed of the sensor platform architecture, sensor network hierarchy, and associated software framework. The main approach consists of empowering the sensor network by using surrogate code located on the sensor node to allow interpretation of the data and sensor node control. Our sensor network hardware platform includes RF communications, EEPROM for data storage, EEPROM for surrogate storage, and microprocessor for communication and data manipulation.

Funding

National Science Foundation

People

Dr. Sumi Helal
Dr. Joachim Hammer
Jinsuo (Allen) Zhang
Young Park
Gargi Sur
Abhinav Kushraj
Mike Lanham
Ajay Kang

Publications

• A. Helal and J. Hammer, "UbiData: Requirements and Architecture for Ubiquitous Data Access," SIGMOD RECORD, Vol 33, No. 4, December 2004. ( pdf)

• Jinsuo Zhang, Abdelsalam (Sumi) Helal and Joachim Hammer, "UbiData: Ubiquitous Mobile File Service," Proceedings of the ACM Symposium on Applied Computing (SAC), Melbourne, Florida, March 2003 (pdf).

• M. Lanham, A. Kang, J. Hammer and A. Helal , "Format-Independent Change Detection and Propagation in Support of Mobile Computing," Proceedings of the XVII Brazilian Symposium on Databases (SBBD), Gramado, Rio Grande do Sul, Brazil, October, 2002 (pdf).

• A. Khushraj, A. Helal and J. Zhang, "InCoda: Incremental Hoarding and Reintegration in Mobile Environments," Proceedings of the IEEE/IPSJ International Symposium on Applications and the Internet (SAINT), February 2002, Nara, Japan (pdf).

• A. Helal, J. Hammer, A. Khushraj and J. Zhang, “A Three-tier Architecture for Ubiquitous Data Access” Proceedings of the First ACS/IEEE International Conference on Computer Systems and Applications, to be held June 2001, in Beirut, Lebanon (pdf).