One of the main difference between MetaView/ GIS and the 
other directory services is the ability for a user to specify 
queries using region selection. MetaView/GIS maintains two 
types of databases: one contains map data, the other contains 
the metadata. The map database contains data for displaying 
maps of the world. The other database maintains the 
metadata, directory, catalogue, etc., of data sets in other 
databases. The first database is internal to the 
MetaView/GIS system, and users cannot therefore influence 
its organization and/or modification. The metadata database 
is however available for updates by certain category of users. 
There are two main users of the MetaView/GIS system; 
those who will maintain the data in the database and those 
who will interact with the database to access information 
about data sets and databases. 
The MetaView/GIS software is organized on a client/server 
model. The server has the MetaView/ GIS databases. A 
client runs at the user’s site. Queries by the users are 
bundled and transferred to the server, which retrieve the 
necessary data from the database and return it to the client. 
Similar to the Delta-X, the communication between the 
client and the server is done in an asynchronous mode over a 
communication network. As shown in Figure 2, the Delta-X 
clients and servers, are basically, the MetaView/GIS servers 
and clients. 
3.2 MetaView/GIS Server and Clients 
The MetaView/GIS server interfaces between the 
MetaView/GIS clients and the databases of the system. 
Similar to the Delta-X, the MetaView server is responsible 
for transaction management; this includes the monitoring 
and scheduling of transactions, the authentication of client 
requests, the administration of resources and the 
commit/abort of transactions and recovery. Further, other 
MetaView Servers has the capacity to store, execute and 
manage data requests, connect to a client to transmit data, 
communicate with other MetaView/GIS servers for 
assistance when necessary and authenticate MetaView/GIS 
privileged clients. 
Visual queries involve first invoking a display of a globe, 
and then determining a region or an area of a globe where 
information is desired. A user can invoke this facility of 
MetaView/GIS by opening the map database. A user may 
zoom in on an area to facilitate more precise region 
selection. The selected area is interpreted as the bounding 
coordinates and is transmitted to the “Search region" in the 
Database Information Window. A user can also specify the 
search region manually for searches to be constraint within 
the region. The provision of visual spatial querying 
capability is one of the main distnguishing features of 
MetaView/GIS. 
3.4 Metadata Update Functions 
There are essentially, two classes of users of MetaView/GIS. 
A general public user and a privileged user. The privileged 
clients are the database owners that provide the metadata of 
their databases/data sets to the MetaView/GIS database. 
The owners of the databases or the data sets need to insert 
data in MetaView/GIS database, and to update existing 
information.  MetaView/GIS provides a more flexible 
approach and friendly entry forms for these purposes. 
Updates made by authorized user are logged in temporary 
tables in the database. These changes are actually effected 
by the database administrator (DBA). 
3.5 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 ftp or telnet to another machine to transfer data. These 
systems use third party networking 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. 
Also, other MetaView spatial browser services include SQL, 
for advanced users who may wish to interact with the 
MetaView/GIS databases directly, and Delta-X for the 
The MetaView client includes the GUI portion of the MV/GIS 
software that runs at the user's site. When MV/GIS is started 
it first displays its top level window as shown in Figure 4. At 
the top level a user has the option of connecting to Delta-X to 
convert data stored in one format and to transport it to users. 
access, retrieval of data sets from databases in the 
federation. MetaView provides access to other directory 
services. 
4. CONCLUSIONS 
Although the Delta-X and MetaView/GIS spatial browser 
work with geospatial data, its architecture, design and 
implementation can be applied to any type of data. The 
successful implementation of both systems in our Division, 
provided unprecedented capabilities to all the GIS 
workstations on our network. Our users can browse through 
the directory and metadata database of the federal 
government data holdings developed by the Inter Agency 
Committee on Geomatics. Data transfer between the various 
GIS databases and standard file formats are further proof of 
3.3 Queries 
The Spatial Browser is used to search the database by any of 
the following options: keywords, data set name, category code, 
category name, agency/owner name, contact person name, 
database name, application name or project name. The 
Summary button gives a summary of the data sets in the 
database. 
6 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996