Alphanumeric and graphic query stations and a large range of peripheral de- 
vices can be connected to any of the above workstations. Refer to previ- 
ously published papers [Hügli 1985, Mc Laren 1986] for more informations. 
S9-D and S9-E will be delivered in autumn 1986, S9-AP and S9-S in early 
1987. 
The core of the SYSTEM 9 software is a software package called the Kernel 
which is present in all workstations. The Kernel provides the functions 
to manage the project and data flow, to store and manipulate data using 
the relational database management system and to drive the different 
devices such as graphics displays, digitiser, plotter, command input 
screen, plotting tables, etc. 
Various application packages are built on top of this kernel toolbox and 
make full use of the database management system. These packages include: 
- data capture and editing from existing maps (S9-D) 
- photogrammetric data capture and editing (S9-AP), including a photo- 
grammetric preprocessor 
- input and processing of field-survey data, a "geodetic" preprocessor 
- digital terrain model, including profiling, perspective views and volume 
computation 
- aerial triangulation programs for bundle and independent-model methods 
- polygon overlay analysis packages 
- data interchange modules for transfer of BC2/RAP2 and Intergraph data- 
files 
THE SYSTEM 9 DATA MODEL 
It is evident that conventional techniques for capture of spatial and 
attribute data must be much enhanced or even replaced to cope with the 
complex data structures and specifications of geographic information 
systems. The following demands are more and more often required: 
- Flexibility in database definition to allow the user to structure the 
database for his data-set model 
- Consistent topologic structuring of the data set 
- Sharing of primitives (points, lines, surfaces) among features of dif- 
ferent classes 
- Ability to create and access complex features, such as parcels, which 
reference simple features such as parcel boundaries, houses and land 
use on a parcel 
- Ability to synthesise polygons from geometric primitives (lines) in 
real-time or in batch mode 
- Strict quality-assurance procedures requiring automatic checks for topo- 
logic and topographic errors (e.g. a street crosses a house) and storage 
of information on quality with nodes 
- Relating attribute information to data at various entity levels 
Given these extended requirements, it was clear that a new data model had 
to be defined for SYSTEM 9. Fig. 1 gives an overview of the selected 
model. 
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