Maps Attr ibutes 
  
  
| 1 
  
  
  
Graphics Input [Attribute Management Attribute Output 
  
  
  
  
  
  
Graphics Pre-process 
1 | 
Graphics Operation||Image Operation 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Digital Terrain Model 
  
  
  
  
  
  
Geo-model Analysis 
  
  
  
  
  
Graphics and image output 
  
  
  
Fig. 4 The structure of MCGIS. 
MOGIS uses Geo-Code Model (GCM) to describe 
geographical attributes.GCM reasonably grades 
geographical factors and uses symbol strings, 
such as digital strings and literal strings, 
to express geographical attributes. Every bit 
in those strings represent different 
attribute, with its value representing the 
attribute value. 
Vector and raster (grid) are two basic 
graphics data formats used in MCGIS. Vector 
data is mainly used to input graphics and 
calculate geometric data (area, length etc.), 
and raster data or images is mainly used to 
operate graphics and images.MCGIS defines two 
basic image operation, that is, image overlay 
and image extract, both of which are based on 
the GCM-expressed geographical attributes. 
Image overlay can be expressed as 
11+12+13+...+In —> I 
where 
(1)-11, 12, ..... ,In are as independent 
geographical factor images (raster maps); 
(2) I as an integrative geographical factor 
image,which is composed of I1, I2,...,In. 
Image extract is the reverse calculation of 
image overlay,which can be expressed as 
I -»"Ti1-I2TI2t0... 1n 
that is,getting some dependent or independent 
geographical factors from an integrative 
factor. 
Generating Digital Terrain Model (DTM) is 
another important function of MOGIS. DTM can 
be expressed as 
Ti=Fi(x,y) 
where 
(1) Ti as topographical factors, such as 
elevation,aspect,slope etc; 
(2) Fi as the function of topographical 
factors to geographical coordinates (x,y). 
MCGIS also uses a series of mathematic 
methods to solve geographical problems with 
271 
known models.Those mathematic models includes 
multiply regression analyses model, tendency 
analyses model, cluster classification model 
and principal component analyses model and so 
on. 
2.2 GKB — geographical knowledge acquisition 
and management system of MCGES 
As a branch of AI applications, expert system 
uses knowlege as logical kernel. Geographical 
knowledge is the logical association of 
geographical data, such as, geographical 
planning, experience and phenomena.Therefore, 
geographical knowledge must be acquired from 
geographer. The level of acquisition and 
management of geographical knowledge is an 
important factor to show the level of GES. 
Knowledge acquisition includes knowledge 
representation and knowledge refinement, and 
the former is the most important one. 
Geographical knowledge representation may be 
defined as expressing geographical knowledge, 
such as planning, experience and phenomena, 
with abstract logical languages that can 
be understood by computer. This kind of 
expression can be inputted to computer and 
stored in knowledge base. 
After analysising geographical research 
contents, we devide geographical knowledge 
into following three levels: 
(1) the basic level,which describe and grade 
the geographical independent factors, is based 
on GCM; 
(2) the medium level, which classifies 
integrative geographical factors, is a group 
of classification rules; 
(3) the advanced level is a series of 
integrative geographical planning rules. 
A kind of list language is designed to input 
geographical knowledge in MOGES,and there are 
several functions in the knowledge base 
management module or sub-system (see Fig.5). 
2.3 GIE — reason controlling module of MCGES 
Inference engine controls the inference 
operation of the knowledge in the knowledge