CS8803 Course Reading Summaries
Paper #: 5.2 19
Title: Sleepers and Workaholics: Caching Strategies 

in Mobile Environments. Daniel Barbara, Tomasz 

Imielinski,VLDB Journal 4(4): 567-602(1995). 

Caching of frequently accessed data items will be 

critical procedure that will reduce contention on 

the narrow bandwidth channel and low processing power

 of the network as mobile devices have a tendency to

 disconnect from a network frequently, due to power 

saving and short battery life. The authors of the 

paper with these problems try to put forward a 

solution so that mobile devices continue to receive 

up to date data and can use network resources for

 maximizing their query runtime.

The author of the paper presents to the reader three

 solutions to the problems. The first solution put 

forward by the author is the idea of timestamps. 

After a certain time period the server checks if 

the information needs any updating and if it does,

 it fetches the current upto date information. 

The author then presents the Amnesic Terminals, in 

which items that have changed since the last 

invalidation report are notified by the server. 

Lastly, the simple idea of checksum is presented by 

the author. Here a checksum is performed on the 

current and the latest data. If the checksum differs, 

this means that the current data is not upto date 

with the latest data and hence a synch is required 

on the current data. A great deal of mathematical 

analysis is presented for scenarios in which of the 

above mentioned procedure will be relevant. 

 
On hindsight writing critiques in 2009 for the paper

 that was written in 1995, one can definitely come 

up with a lot of obvious weaknesses in the paper. 

The state of the network now in 2009 is much more 

sophisticated and robust with a wide range of video

 intensive applications such as YouTube and Hulu 

being extensively used by users. This was not the 

case in 1995 and hence the author lays a lot of 

emphasis on network bandwidth and network processing

 power. The mobile devices themselves have been 

greatly improved with IPhone having 32GB of storage

 capacity and hence the idea of caching on these 

devices periodically is not a major challenge any more.