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values corresponding to the concerned data set. 
Changes can now be made by the user. The modi- 
fied data or newly inserted data is logged in tempo- 
rary tables in the database. These changes are 
actually effected by the database administrator 
(DBA). 
37 Other MetaView/GIS facilities 
The main window of the browser, allows users to 
make request by using either and on-line or off-line 
tool. A user can fip or telnet to other machine to 
transfer data. These systems use third party net- 
working software for their functions. An off-line 
request can also be made by a FAX. The system 
prepares a fax report for the user based on the data 
set that is presently being accessed. A handy mail- 
tool is also available for users. These functions can 
be accessed with the menu Request/Off-line/Fax 
and Request/Off-line/Mail. 
The browser also has gateways to other directory 
services. Briefly these services are: 
e SQL: This is provided for advance users who 
may wish to interact with the MetaView/GIS 
databases directly. Based on the server’s vendor 
database. 
* DeltaX: A tool for the interchange of GIS data 
formats. A complementary system of Meta- 
View/GIS. 
* GCNet: A directory service developed at 
SMRSS, NRCan for researchers, scientists and 
users of remote sensing information. 
* Mosaic: An Internet information browser and 
WWW client of NCSA. A user can connect to 
most directory services from here. 
* Archie: The Archie information system is a net- 
work-based information tool offering pro-active 
data retrieval and indexing for widely distrib- 
uted collections of data. Perhaps the best known 
application of the Archie system is to maintain 
the Internet Archives database. 
e FreeNet: A National Capital FreeNet informa- 
tion service based in Ottawa, Canada. Users can 
connect to other FreeNets across the globe. 
4.0 Administrative functions 
The administrative functions in MetaView/GIS 
include the registration of new privilege users and 
the maintenance of the MetaView/GIS databases. 
A privilege database vendor must be registered and 
given an account so as to enable him/her to input 
his data into the database. The administrator also 
runs programs that will reflect modification of 
existing data items and changes to the database. 
Apart from the DBA, no other user of the system 
can issue a commit transaction on the spatial data 
that is assessed in the database. Transactions of the 
database vendors commit, into tables that are not 
assessed by other users of the system. All tables are 
created with journaling option. Thus the underly- 
ing database management system (Ingres and Ora- 
cle) keeps a record of all changes to the tables. The 
DBA uses these journals for monitoring updates 
and for maintaining change histories. 
A strict set of referential integrity rules are defined 
on the database tables. As much as the system can, 
new data items are cleaned up. On failure to meet 
the integrity rules, a message is transmitted back to 
the database user about the problem. Since the 
DBA (of the GIS vendor site) is the only one who 
can update the MetaView/GIS databases, the 
autonomy of the database is always maintained. 
The disadvantage here is that changes made by the 
database vendors do not get reflected in the Meta- 
View/GIS database immediately. 
369