Jiulin SUN[1],
Songcai YOU[2],
Shunbao LIAO[3]
(Institute of Geographic
Sciences and Natural Resources Research,
The
Geodata sharing is one of nine pilot projects of Scientific Data Sharing
Program of China (SDSP). Its implementation is divided into three stages, i.e.
experimental stage, construction stage and running stage. Now, the project is
on its second stage.
The objectives of this project
are to collect and integrate data for supporting basic scientific research and
knowledge innovation on the field of earth system sciences as well as providing
service to education and publics. The main data sources are from the online
publication of scientific data produced by all related research projects which
are funded by each level governments. The operation of this data portal (http://www.geodata.cn) is of non-profit.
Based on the analysis, metadata
and its relative techniques and data policy play key roles in scientific
clearinghouses, these key issues must be discussed and resolved.
1. Standardization
of Geodata
Geodata
producers have typically developed their own collection methods, attribute
catalogs, data types and formats, which were particularly suitable and designed
for their own applications. This variety was sensible, because new methods and
ideas could be tested without the counterproductive pressure to standardize.
However, along with the quickly increasing availability and use of geodata, it
has also come increasing difficulties resulting from the immense semantic and
structural variety which can now be found among geodata sets. For these
reasons, there has been a push for the development and implementation of
geodata standards. Such standards exist for a variety of areas (semantics,
syntax, metadata, interfaces). Now, as the result of the specific needs of each
of the widely varying thematic application areas which use geodata, so many
standards and standard modifications have been developed, that it is difficult
to give a summary of the standards themselves. For to manage the data distributed in different
locations via metadata through internet, we analyze the existing metadata
standards such, FGDC, ISO 19115, China sustainable development metadata, etc
and found that all elements in the metadata could be classified into three
layers. The first layer is a set of key elements, which is called as core
metadata, these elements are common to all datasets; the second layer is a set of
elements for specific subject, which is called schema metadata; the third layer
is application profile metadata. This classification is important to the
development of management systems.
Data Classification is the conscious decision
to assign a level of sensitivity to data as it is being created, amended,
enhanced, stored, or transmitted. The classification of the data should then
determine the extent to which the data needs to be controlled/secured and is
also indicative of its value in terms of Business Assets.
The
classification of data and documents is essential if you are to differentiate
between that which is a little (if any) value, and that which is highly
sensitive and confidential. When data is stored, whether received, created or
amended, it should always be classified into an appropriate sensitivity level.
A simple 5 scale grade will suffice as follows: top secret, highly
confidential, proprietary, internal use only, public documents. This
classification must be followed by data publishers, data managers and data
users.
For to avoid and reduce the
rebuild of metadata standards, and reuse existed metadata standards as more as
possible, a metadata extension model based on the analysis of metadata
standards status is developed. The model is composed of 3 tiers, i.e., core
metadata, schema metadata and application profile metadata. Geosciences
metadata extension framework is designed and developed based on XML Schema
techniques. According to the specified core metadata, several metadata
extension instances are implemented, such as geosciences core metadata,
geography core metadata and remote sensing application metadata. Metadata
extension also provides Web application interfaces. Geospatial information
services interfaces are defined through 14 extended metadata elements.
Keywords: Metadata, Data sharing,
Geosciences clearinghouse, Metadata extension, Policy
[1] Jiulin SUN, male, born in 1937, Professor, Academian
of Chinese Academy of Engineering, focused in resources management and
agricultural resource information studies. E-mail: sunjl@cern.ac.cn, Tel: +86-10-64889266 ,
[2] Songcai YOU, male, born in 1963, Dr. of
Engineering, Associate Professor, focused on geodata sharing and global change
studies. E-mail: yousc@igsnrr.ac.cn,
Tel: +86-10-64888890 ,
[3] Shunbao LIAO, male, born in 1966, Dr. of Science, Associate Professor, focused on renewable resources information management studies. E-mail: liaosb@igsnrr.ac.cn, Tel: +86-10-64889448