200 
6. China Ministry of Construction Land classification 
system, which includes Level I and Level II types. 
Level I is divided into 3 types, i.e., Agriculture land, 
Building land and Virgin land. Level II is divided into 
15 sub types. 
2.2.3 Application profile classes 
Application profile classes are designed based on core classes 
and corpora classes according to the requirements of different 
research targets. Its extension principle and method will be 
discussed in section 4. 
3. LAND USE/LAND COVER CLASSIFICATION 
STRUCTURE 
Based on the extension framework mentioned above, the land 
use/land cover extensible classification structure is designed. It 
includes content structure, semantic structure and syntax 
structure. 
3.1 Content structure 
Content structure is the concept model of classification system. 
It reflects the classification system’s function. In other word, it 
has hierarchy architecture from top concept layer to down 
concrete elements. Usually, this structure can be designed and 
implemented supported by UML, ERWin, Visio, etc. 
Extensible land use/land cover classification’s content structure 
can be divided into classification section, sub-section, and 
element (figure 3). Classification section refers to the collection 
of related sub-sections and elements. Sections are allowed to 
have the nesting relationship. Classification element is the basic 
unit of the content structure. It has multi-attributes, which will 
be introduced in semantic structure. 
Figure 3. Content Structure of land use/land cover classification 
Although in a uniform framework, different application or 
different discipline field has various classification content 
structures. Thus there has a descriptor indicating whether a 
classification section or element shall always be selected or 
sometimes be selected. This descriptor may have the following 
values: M (mandatory), C (conditional), or O (optional). 
• Mandatory (M): The classification section or element shall 
be selected. 
• Conditional (C): Specifies an electronically manageable 
condition under which at least one classification type or 
element is mandatory. 
• Optional (O): The classification element may be selected 
or may not be selected. Optional classification elements 
have been defined to provide a guide to those looking to 
fully distinguish their data, ments only become mandatory 
if the optional entity is used. 
3.2 Semantic structure 
Semantic Structure is used to define classification elements’ 
concrete description style. It is the base of “common 
classification standard”, “best practices” or “user-defined 
semantic description instructions”. Element’s semantic 
meanings can’t be divided. Its semantic structure is designed 
based on the ISO IEC 11179-3 standard as follows. 
- Chinese Name : Classification type or element’s 
Chinese name 
- English Name : Classification type or element’s 
English name 
- Identifier: Unique Identifier of the classification type 
or element 
- Definition : Introduction of classification type or 
element conception 
- Obligation: classification type or element is optional 
or not 
- Data Type: element’s value type 
- Value Domain: elements’ value domain 
- Comment: Supplement comment for element or other 
advices 
- Remote Sensing Interpretation Sign: Description of 
objects which is suitable for remote sensing 
interpretation by manual or computer 
3.3 Syntax structure 
Syntax structure is the basis of the coding rules of 
classification’s semantic model which is used to describe the 
extension framework. Syntax structure includes element 
description method (e.g., ISO IEC 11179 standard), metadata 
structure description method (e.g., MARC structure, SGML 
structure, XML structure), language description (e.g., Extended 
Backus-Naur Form), etc. 
Which syntax structure is used to describe the application 
classification profile will be selected by the users who will 
implement the classification system according to their 
requirements. Usually, the recommended syntax structure is 
XML schema. 
• XML Schema is suitable for classification element 
definition and relationship description. 
• XML Schema is suitable for interface definition among 
different classification system in an uniform framework. 
4. CLASSIFICATION FRAMEWORK EXTENSION 
PRINCIPLE AND METHOD 
4.1 Extension principle 
Objective of extensible land use/land cover classification is to 
providing a kind of universal classification framework which is