' in 1991, our 
design and 
'ersion of the 
operational 
It of Delta-X 
management 
pport, project 
ntrol. Issues 
>valuation are 
[IVES 
jects are: 
ulti-database 
it provides 
ferent GISs : 
elta-X); and; 
/Ser as a front 
icilitates the 
1s databases, 
fic datasets, 
rage, format, 
t, etc. 
ities 
nalities are 
inctionalities 
The clients 
the database 
d as a server 
. The key 
ace is that it 
; server. The 
ther Motif or 
s capable of 
note X client 
which a user 
er is able to 
tify a dataset 
r a dataset is 
-set owners, 
ng feature of 
allow spatial 
selecting the 
the search. 
Browser to 
ine (E-mail, 
information 
  
Invoking Delta-X from a user workstations 
first establishes connection to a default 
DxServer. Delta-X provides functions for: 
» Displaying selected or all features of a 
vector map, the image or even a digital 
elevation model of a coverage. 
« Retrieving a specific data-set, either 
vector, raster, etc. and translating to the 
user's specific format. 
» Administrative functions such as 
registering and de-registering a database, 
starting up the dxServer after failure, 
authorizing users, etc. 
+ Monitoring the progress of data-being 
retrieved and the state of a ongoing 
transaction. 
Although Delta-X is not a Geographic 
Information System, it has the potential of 
being used in conjunction with other user 
libraries and software for full GIS application 
development. In particular, it provides the 
opportunity for those interested in exploiting 
parallel and distributed processing capability to 
develop algorithms for their specific 
applications. 
3. OPERATIONAL FRAMEWORK 
The work on this project stared with an 
evaluation of the computing systems, GIS 
software packages and database management 
technologies. There were a number of 
emerging technologies and we opted for 
Commercial of the Shelf Components. The 
functionalities of several DBMS' were studied 
and Ingres RDBMS was selected. A spatial 
topological data model was developed and 
implemented. 
The environment we considered for the system 
implementation included: 
* large organizations which often use 
different (and incompatible) GISs to store 
their spatial data in different databases, 
further GISs are nodes connected to a 
Delta-X server in a LAN, 
* anetwork of wide area networks (WAN) 
connecting multiple Delta-X servers; and 
* individual users (Delta-X clients), who are 
authorized to connect over a LAN or a 
WAN to at least one Delta-X server. 
A Heterogeneous GIS environment was 
selected due to the wide variety of GIS 
Software and hardware platforms available on 
the market. The approach we took in our 
349 
solution was to consider the databases residing 
in various agencies to be autonomous. The 
availability of autonomous databases over a 
WAN to users has many implications. First, 
the dataholders must be part of a federated 
environment and the data users must have 
authorization to access data in the federation. 
The federation must allow browsing of 
databases so that users can identify the data 
required and request transfers. Second, the 
data holders manage and control their spatial 
data and metadata, so that data will be up to 
date, consistent, error free and secure from 
unauthorized changes. In this environment, 
the user can browse the metadata database for 
data sources. Data transfer from "donor' to 
user 'target' systems is executed by the Delta- 
X. 
4. MANAGEMENT PERSPECTIVE 
AND TECHNOLOGY SUPPORT 
One of the cost effective methods the Division 
used to see if the users' needs are satisfied 
was to implement a research prototype system 
based on the requirement analysis and to test 
the functional capabilities of the design. This 
way, the concepts that were established earlier 
could be tested on a real system to make sure 
they work. This allowed our team to install 
the prototype on a local area network (LAN), 
make effective assessment of the development, 
conduct performance analysis and establish 
requirements such as storage and display 
capability. The results of these tests made it 
possible for further system enhancements 
towards developing an industrial strength 
prototype system that will meet the challenges 
of data exchanges over a wide area network 
(WAN) without rehashing much of the code 
developed for the research prototype. 
Moreover, the rationale that was followed was 
to use existing technology as much as 
possible. To illustrate this in the context of 
Delta-X, we decided to use PHIGS, RPC, 
Open Windows, MOTIF and INGRES among 
other products. The integration of these 
technologies into Delta-X was necessary for 
the effective performance of the system. The 
conformance to such standard packages helped 
the system designers to make it highly 
portable. 
5. RESOURCES 
A project of this nature needs a funding 
strategy to encourage the developers to reach 
the goals and even surpass them. The limited