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between the physical reality and the model components. 
This implies that operation on the model will produce 
real effects on the land resource represented. Therefore, 
information representing land resources is manipulated 
by both the monitoring process and the land resources. 
3. INFORMATION MODELING 
The amount of information monitored for a large rural 
land monitoring system requires that a structured 
approach be taken to model and represent that 
information. Since many entities in rural land 
monitoring system share common characteristics, this 
characteristics must be exploited in order to maximize 
commonality and minimize implementation efforts. 
These considerations have led to the application of the 
object oriented technique for monitoring rural land use. 
This technique allows the modular development of 
specifications and implementations of monitoring 
system of rural land use. 
3.1 Object Description 
To define an MO (Monitored object) class, the 
characteristics of each instance that is a member of that 
class must be specified. The characteristics of an object 
can be specified as the followings. 
(1)Superclasses of the MO, 
(2) Visible attributes of the object; 
(3)Operations that can be performed on an MO; 
(4)Notifications that may be emitted by an MO as a 
result of internal events; and 
(5)Behavior that an MO exhibits. 
3.2 Modular Package 
To allow additional flexibility in modeling land 
resources, these characteristics (except for the 
superclasses) are collected into modular packages. MOs 
are modeled as collections of packages. Packages may 
be mandatory or conditional. Mandatory packages 
always are a part of each instantiated object. However, 
conditional packages may be absent when an object is 
instantiated. 
3.3 Object Attributers 
Attributes are the named characteristics of an MO. A 
value is associated with each attribute of an MO. Such 
values may be read or modified through internal system 
or monitoring actions. In addition to attributes, the 
concept of an attribute group is introduced. It is a 
named group of individual attributes, and provides a 
shorthand reference to multiple attributes. All 
operations on attribute groups are performed as if each 
attribute had been referenced separately. 
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
3.4 Object Behavior 
The behavior specification for an MO specifies the 
dynamic characteristics of an object and its attributes, 
notifications, and actions. It includes the semantics of 
attributes and describes the way in which monitoring 
operations affect the object and its attributes. Behavior 
also describes the internal events that occur and result 
in observable changes in the object. 
3.5 Operation on Object 
MOs generally represent active entities that exhibit 
their behavior and more through.sSome state space. 
Thus, there is a requirement to be able to control the 
entities represented by the MOs by means of operations 
performed on the MO. Monitoring operations are 
categorized into the followings. 
(DAttribute-oriented operations. Generally, these 
operations allow for the retrieval and setting of 
attribute values. However, these operations, even 
when supported by an MO, are subject to policy 
constraints. These constrains may relate security and 
access privilege limitations. Otherwise, these 
operations obey the encapsulation principle. 
(2)Whole object-oriented operations. These operations 
impact an object’s behavior as a whole without being 
targeted at setting or retrieving attribute values. 
3.6 Notification from Object 
Because MOs represent active land resources, internal 
and external events occurred impact the operation 
modeled by the MO and must result in corresponding 
behavior in the MO. These event are made visible to 
the local monitoring process as notifications that are 
emitted by the MO whenever such an event occurs. In 
addition to events that occur as autonomous activity of 
the object and its environment, the object also may be 
impacted by monitoring operations. 
3.7 Object Inheritance 
Object-oriented modeling allows specialization of one 
MO class from another. A class derived from another 
class is referenced to as a subclass of that class. 
Otherwise, it in turn is refereed to as its superclass. A 
subclass may be specialized from a superclass by 
modifying the characteristics of the superclass. For 
rural land use monitoring, such modifications are given 
as the following. 
(1)The addition of new monitoring operations and 
notifications; 
(2)The addition of new attributes and attribute groups; 
and 
(3)The addition of new compatible behavior. 
  
  
  
  
  
  
  
  
  
  
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