Information Systems. In this last area, HBDS is the 
standard for geographical data structuring at the 
Institut ^ Géographique National in France 
(Dassonville, 1991). 
Basicaly, HBDS is composed of six basical abstract 
data types (indicated here as "a.d.t."), respectively 
named: 
—class, attribute of class, link between 
classes, these three a.d.t. composing the 
"structure skeleton", 
—object, attribute of object, link between 
objects, these three a.d.t. composing the 
"realizations". 
Figure 1 shows the graphical representation 
associated to each a.d.t. . 
  
attribute 
of class 
attribute 
of abject 
    
  
   
Link between 
classes 
     
link 
between 
  
objects 
  
  
Fig. 1 : Graphical representation of the six basical 
abstract data types. 
An attribute has a kind, a type, possibly predefined 
values, a possible unit when digital, a given type of 
fuzziness, and various other features we cannot 
detail in these few pages. The different kinds are: — 
scalar, -array (distinguishing vector, matrix and 
tensor of any size), -list (circular or linear) — 
compound (looking like a C-structure or a Pascal 
record). 
Arrays may be built as "sparse", when there are 
many missing values, for instance, and this 
capability concerns vectors, matrixes and tensors. 
The possible types are : —integer, —float, —complex, 
—gauss (Gauss complex), -quaternion 
(Zhypercomplex, very usefull in robotics), —rational, 
-boolean, -character, -string (of any length, 
extensible as necessary without previous declared 
length ). 
Digital types may be built as "long", thus having any 
number of digits. 
Links between classes carry a potential relationship, 
whereas links between objects represent an effective 
relationship verified by a couple of objects. 
In HBDS, all the a.d.t. are considered as implicitely 
persistent.The first extensions are three a.d.t, 
respectively named : hyperclass ( a set of classes), 
hyperattribute (attribute carried by a hyperclass and 
40 
inherited by all the classes included in this 
hyperclass), hyperlink (link starting from a 
hyperclass, or arriving on a hyperclass, and thus 
inherited). Figure 2 shows the graphical 
representation of these new a.d.t. 
  
hyperattribute 
  
Tes 
hyperclass | oF 
hyperlink 
Ce 
RE 
  
  
  
  
  
Fig. 2 : The three first extensions. 
Hyperclasses may intersect or embed others, thus 
providing a multiple inheritancy. The second 
extensions are respectively named embryo, 
prototype and structure. An embryo looks like a 
basical a.d.t. of the skeleton, but with no realization; 
it is used for assembling with others, composing a 
prototype (Bouillé, 1993b); it is just a model, which 
copies will provide structures, each structure 
receiving afterwards more specific attributes and/or 
links corresponding to its specific phenomenon 
features. The figure 3 shows the graphical 
representation of a prototype, named "GRAPH", 
representing all the topological relationships 
between vertices (improperly named "nodes"), arcs 
(also sometimes named segments) and areas, as it 
may be found in most of geographical themes. 
  
Prototype 
  
  
  
  
  
  
  
  
  
  
  
Fig. 3 : From prototype to structures. 
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