2.3 Implementing approach of integration
The characteristics of GIS software integration are focused on the functions of graph and
image processing, connecting between spatial data and related attribute data, and spatial
analyzing etc. Hence, it is necessary to be supported by the visual developing environment for
GIS software integration. At present, developing tools for integrating GIS applications are
provided as follows: Visual Basic, Visual C
++, Visual FoxPro and Delphi, Power Builder etc.
The “component integration mode” is a major and important approach to implement integration.
It means consisting of controllers provided by the environment and the commercial GIS
software, and OLE automatic object based on integrating target.
During the procedure of component integrated, it is important to understand well about
“event driving mechanism”. And it is used in the applying software and working mode of
graphic user interface. To the different events, various controllers are prefabricated for graphic
interface in visual developing environment. They are: window events, mouse events, and get or
lose events etc. For every event of various objects, the system will be produced a corresponding
information and passed it to the information response function or procedure. Because of the
event driving mechanism, its controller right is given to the user and the system. It is not
necessary to distinguish the user’s operation and to consider the control procedure of
programming workflow but just to concentrate to execute the function of the system for the
developer.
The technical procedure of GIS software integration is included in interface design, class
module creation, and function development of API (Application Programming Interface). A
design of multimedia interface is mainly focused on using MDI (Multiple Document Interface)
technique and designing and organizing the menu and tool bar. Multitier menu is not only
presented an optimizing organization but also user interface of event driving mechanism in
visual integrating environment. Menu design is incarnated a technical style of the system
designer and the deepness of his or her understanding to the user’s manipulating custom. The
purpose of creating class module is mainly used to encapsulate program paragraph and made it
repeatable and usable easily. Class module can be function module and also be repeatedly called
program paragraph in the integrated system; at the same time, the class can be used to create
ActiveX component in which it is defined by the class and the object is an instantiate of the
class. Class module creation is included: setting, defining class attribute; writing a procedure of
the class to create method and to give codes of the processing event. Actually, the class is
encapsulated the attribute, method, and event to repeatable objects, and executed a specific
function through creating object instantiate defined by it. But, all the controllers, which were
provided by commercial GIS software and visual developing environment for integrating, are
not properly satisfied the demands of function integration. Taking an example of Visual Basic,
graphic function is its weakness. At this situation, API function needs to be called. Windows
API is consisted of four function classes, they are windows management, interface of graphic
device, system service and multimedia. API function can be called in any developing language
in dynamic link library (DLL). Therefore, API function will be a reserving technique support to
the component integration Model in implementing a certain target of software integration.
III. Practice of Component Integration
3.1 Integrated practice with selected commercial GIS software
The aim of GDLMIS (Guangdong Landuse Management Information System) construction
is to store land information scientifically, to update the maps and document timely, and to have
a good command of land resource and its utilization state in the whole province through
querying. And the system is also needed to provide decision making support for land
management, cultivated land protection and modern agricultural allocation etc. The major data
sources were recent landuse maps and update maps with various scales 1:500,000 for province,
1:50,000 for cities and counties, and even more detail 1:25,000 in mountain area, 1:10,000 in
agriculture area for the towns and valleys class. The system is also proposed to create updating
landuse maps using multidisciplinary analysis and conclusion with remote sensing image, field
inspecting data, and red line maps of the land owner etc. Various data sources. Hence, the
characteristics of the system construction is large amount and various sources of data, and many
models are needed in the system including RS (Remote Sensing) information processing,
applying and decision making support model. As the result, a concept model of the integrating
system was designed as follows in figure 1.
Fig. 1 A Concept Model of Integrated System for Guangdong Land Information Management System
3.1.1 Component integration
According to the aim of the system construction, its functions need to be included in strong
graphic edit, systematic query and spatial analysis etc. It is necessary to furnish controllers and
programmable objects as basic components under the support of OLE automation from modular
commercial GIS software for creating user interface in the concept model of the system. The
menu system of the user interface is a logic organization of all the functions in the integrated
system. The multitier design of the menu system is not only considered the logic relationship
between functions but also taken serious of logic relationship between controllers and
programmable objects. The later one looks like a programming problem. Actually, it is an
important factor that is given strong influence on reliability of the integrating system. Another
important part of the user interface is tool bar which is presented the graphic shortcut of the
common tools on the desktop for the system. In view of the module feature and such integrating
object of tool bar provided from the commercial GIS software selected, Tool Bar Button in each
module can be arranged into user interface. This feature makes the integrated system reflecting
a much better flexibility.
As is known to all, there are no usable controllers and programmable objects in digital
image processing functions. In this instance, OLE technique is used to insert the image
processing module into the system and to implement its every function. At the same time,
image processing module can be translated into Chinese partly, and made it properly
coordinating with the interface of the system.
3.1.2 Class module creation
In general, user interface is a constructing procedure of component integration, and class
module creation is really an implementing procedure of the system integration. A class is not
contained programming groups of the control under Visual Basic integrating environment.
Usually, class module is consisted of a few in common with programming procedures and
functions. They create the methods of the class models. During implementing procedure of a
method, an operation is called to executing or getting user’s response information from
“container” – form with controller. And according to the different response event of the user,
the event procedure is driven taking an example as clicking OK or clicking Cancel. In fact,
user’s response information is a message assigned value to the variable and passed to the class
module executing the task assuming responsibility of class module. For example, mod Record
Sets is one of the frequently called modules. It contains two methods that one is created Record
Set; another is recorded classified and statistical set. The method of creating Record Sets is
called feature form selected and displayed the names of the database and the tables by user.
After user selected, the “task” of the module is driven to open the operation of the database; if
there is no related graph displaying the graphic window, a class module of graphic display is
called to execute the graph displaying. Another example, mod Buffer Zone is a typical function
module in which contains three methods; they are creating buffer zone, selecting distance of the
buffer zone and getting coordinate information. Through calling the module, it is defined the
center position of the buffer zone, calculated the exact distance based on the coordinate of
projection and scale provided by the user, and finished the display of buffer zone position
according to the selected point, arc or polygon.
