The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
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find the corresponding GML fragment when retrieve original 
data file. In addition, structure of document such as relationship 
and order between elements might be disarranged. Thus, these 
factors certainly will bring difficulties to management and 
retrieve of document data. 
<?xml version="1.0" encoding="UTF-8"?> 
<xs:schema 
xmlns:xs="http://www.w3.org/2001/XMLSchema" 
elementFormDefault="quaiified" 
attributeFormDefauIt="unqualified"> 
<xs:element name="root_LogFiles" 
type="FileColIectionType"/> 
<xs:element name="WholeFile" 
type="WholeFileType"/> 
<xs:element name="SegmentFile" 
type="SegmentFileType"/> 
<xs:complexType name="FileCollectionType"> 
<xs:sequence> 
<xs:element ref="WholeFile" minOccurs="0" 
maxOccurs="unbounded"/> 
</xs:sequence> 
</xs:complexType> 
<xs:complexType name="WholeFileType"> 
<xs:sequence> 
<xs:element ref="SegmentFile" minOccurs="0" 
maxOccurs="unbounded"/> 
<xs:element name="Store_Time" 
type="xs:string"/> 
<xs:element name="Store_Member" 
type="xs:string"/> 
</xs:sequence> 
<xs:attribute name="name" type="xs:string"/> 
</xs:complexType> 
<xs:complexType name="SegmentFileType"> 
<xs:sequence> 
<xs:element name="SegmentFileName" 
type="xs:string"/> 
<xs:element name="ColletionPath" 
type="xs:string"/> 
<xs:element name^'ChildSegmentFileName" 
type='’xs:string" minOccurs="0'7> 
</xs:sequence> 
<xs:attribute name="narae" type="xs:string'7> 
</xs:complexType> 
</xs:schema> 
Table 2. log schema file 
Then, how to manage these GML documents stored in database ? 
The approach this paper adopted is to define a storage log file 
for each partitioned GML document after stored in database. 
Data file with the same schema corresponds to one storage log 
file, this log file save relevant storage information for each 
GML document stored in database, includes: GML fragment 
name, GML fragment storage position, fragment order and 
metadata about GML document storage such as saving time, 
saving person and so on. 
Since information of each log file is basically fixed. Thus, it s 
necessary to define a standard log schema file. In this way, log 
file could be customized according to schema file. We use 
XML format to describe log file, in the same way, we also use 
XML format to describe standard schema file. 
Definition of storage information for fragment document as 
follows, element SegmentFileName indicates fragment file 
name, element ColletionPath indicates path the fragment file 
stores. Element ChildSegmentFileName indicates file name of 
features that would be nested by feature corresponds to this 
fragment. 
Definition of storage information for the whole GML document 
as follows, element SegmentFile indicates relevant information 
of partitioned fragment file, element StoreTime indicates store 
time of this document, element StoreMember indicates the 
store person of this document. In addition, extend relevant 
information according to requirement. 
FileCollectionType indicates storage information of different 
data file with the same schema. 
According to definition of above nodes, log schema file could 
be defined as following table. Thereby define log file by this 
schema file. 
Thus, when store instance document City.xml, user can define a 
log file to store information of document partition according to 
this log schema file, consequently facilitate later operation and 
retrieve. Log file of City.xml generated on the basis of log 
schema file is omitted in this paper. On this basis, log file of 
city.xml and city.xsd schema file could be stored in 
corresponding management collection. In this way, GML 
instance document, GML schema file and storage log file could 
be stored in native XML database and implement native based 
storage of GML data. 
3. DESIGN AND IMPLEMENT OF G2NXDBM 
PROTOTYPE SYSTEM 
3.1 Design of G2NXDBMs Framework 
This constructed G2NXDBMs prototype system, Figure 4 
shows frame sketch map of this system architecture. 
G2NXDBMs prototype system mainly implements storage 
management on GML data, GML schema and metadata by two 
modules: GML storage and GML query. 
Figure 4. Architecture of G2NXDBMs 
Design idea and function of GML storage module could be 
described as follows: ©analyze GML application schema 
document, generate one to one mapping rule between schema 
and storage structure; ©establish relevant collection in