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Kôlbl, Fadli, Boussalh, Hostettler, Hunziker 
3. ELEMENTS OF AN INFORMATION SYSTEM 
It is thus advisable to define first the basic elements to be surveyed, to establish the relationship between these elements and then to 
combine them to form objects. This cycle can be repeated thereafter to form combined and complex objects. 
3.1 Basic Elements 
By referring now to the historic monuments, we can define the following basic elements: 
• Body of constructions: 
o Dwelling houses, simple houses or houses with inner courtyard, etc. 
o Community objects: mosques, granaries, etc. 
o Particular constructions: ramparts, protective walls, defence towers, etc. 
• Ornaments (fig. 1): 
o Façade ornaments 
o Door frames 
o Door ornaments 
o Window frames, window and grille ornaments 
o Gutters, etc 
• Squares 
• Lanes 
• Infrastructures: drinking water, waste water, electricity, telephones, etc. 
During the pilot project different tests were carried out to capture these elements. When designing the current catalogue of the data 
base to be used, a reclassification was made and a number of new elements were added, but the initial structure was basically 
retained. 
3.2 Agglomeration of Individual Elements (Local Level) 
The agglomeration of different elements thus form the villages (ksour) or the kasbahs. For these constructions, the architect usually 
uses plots and oblique images to present their typical aspects. 
3.3 Regional Level 
The entire set of different towns, their interconnection as well as the agricultural land surrounding them define the living area of the 
population. Consequently, it is important to make a reference to the regional information, the main land use, the infrastructure of the 
communication network, the agricultural land and the water supply. It is also advisable to add other information levels such as the 
economic context or the possibilities to increase the income of workers in craft industry, industry or tourism without forgetting agri 
culture. To be credible, it is understood that this work has to be done in relation with already existing inventories. 
This economic network should be connected with the ethnic component, which still defines very strongly the region and which could 
help in understanding the development and the specific aspects of the historical monuments. 
4. GENERAL REFLECTIONS ON THE DATA MODEL 
A geographic information system is a relatively complex system but may offer great flexibility for the management of the informa 
tion coming from the inventory of the historical monuments. An attempt is made below to recapitulate the basic elements of an 
information system in connection with such an inventory: • 
• Geometric information 
• Image information (raster data and symbols) 
• Semantic and descriptive information 
4.1 Geometric Information 
In general, a geographic information system has a drawing surface, which allows representations in 2D or 3D. The basic element of 
this surface are: points, lines, surfaces, complex objects, and in case of 3D systems: cubes, bodies, cylinders, rotation surfaces, etc. 
We can even include in this group the digital terrain model. 
4.2 Image Information 
This information is in general organized on the basis of raster data such as images or orthophotos with strict geometric reference. 
Usually, the individual picture elements cannot be addressed in a logical way, which means that we cannot highlight specific roads or 
other objects by queries, except by sophisticated processes. These elements can be summarized as follows: