We have implemented the two new approaches and tested them on a sample NASA data set. The code was written in Java Programming Language and the tests were run on a Local Area Network. A SUN SPARC ULTRA 1 workstation was used as the server and a Pentium P-166 Processor based PC was used as the client. The Global Change Master Directory Query Preview Panel was used as the basis for the Java Code. The sample NASA data set, with 60275 tuples, was obtained from the NASA V0 Client Homepage. We have used longitude, latitude, and year as our preview attributes. We have also modified the previous code to download this sample data set and incorporated results of this version to our report to show how previous approaches perform with this sample data set in comparison with the two new approaches. Figure 7 shows a snapshot of the Query Preview Panel used in our tests and Figure 6 gives the comparative results of these tests.
|
Approaches |
Approach |
Approach |
|
|
Querying Time |
2-3 seconds |
1-2 seconds |
0-1 seconds |
|
Client Main-Memory Utilization |
750 Kbytes |
None |
50 Kbytes |
|
Setup Time |
25-30 seconds |
None |
10-15 seconds |
|
Server Disk Utilization |
750 Kbytes |
200 Mbytes |
750 + 50 Kbytes = 800 Kbytes |
|
Data Preparation Time |
None |
Within 1 day |
Within 1 hour |
|
Restrictivity Level of the Preview Panel |
None |
None |
1 selection per attribute |
Figure 6: Experimental analysis of the approaches (previous, post-fetch, and pre-fetch).

Figure 7: The Query Preview Panel used in our experiments.