Virtual Observatory Data Access Service (VO-DAS 1.1) |
Virtual Observatory Data Access Service (VO-DAS) is a data access framework, which is developed by Chinese Virtual Observatory (China-VO) project, providing a user to access world-wide big volume datasets, to query different types of astronomical data resources including catalogs, spectrum and images. There are three kinds of user interfaces available, i.e. graphical, command line and webpage.
- Distributed databases support.
- Data resource registry and browse.
- Huge volume dataset support.
- Cross-identification (cross-match) of astronomical catalogs.
- Uniform interface for different types of resources : catalog, spectrum and image.
- Java: Sun JRE
- Container: Apache Tomcat 5.0 or later, which can be downloaded here.
- Web Services: Globus Toolkit 4.0 Java WS Core, which can be downloaded here.
- Middleware: OGSA-DAI WSRF 2.2, which can be downloaded here.
- Database: MySQL 5.0/SQL Server 2005.
- Others: Apache Ant 1.5 or later, which can be downloaded here.
· VO-DAS Server: JRE 1.4.X, Apache Tomcat 5.0.X, Globus Toolkit 4.0 Java WS Core 4.0.X, OGSA-DAI WSRF 2.2.
· Data Node: JRE 1.4.X, Apache Ant, Apache Tomcat 5.0.X, Globus Toolkit 4.0 Java WS Core 4.0.X, MySQL 5.X.
· Storage Server: FTP.
· Registry: Apache Tomcat 5.0.X.
· Client: 1.Graphic and command Line: JRE 1.4.X
2.webpage: browser: IE 5.0 or FireFox 3.0 server: JRE 1.4.X, Tomcat 5.0.X.
VO-DAS server:
- For Windows: Please download the “tar.gz” file here (about 28MB) in which VO-DAS server has been deployed.
- For Linux: Please download the “tar.gz” file here (about 38MB) in which VO-DAS server has been deployed.
VO-DAS client:
- Please download the “tar.gz” file here (about
Registry
· Please download registry template included in “tar.gz” file here (about 0.27MB). edit it to adapt for your requirements.
Data Node
· Please download metadata template included in “tar.gz” file here (about
Storage Server
· FTP is only supported in VO-DAS system and 159.226.169.222 is available for use. If you want to use it, please send E-mail to yyang@lamost.org. You can also use other FTP servers available for you.
Installation Guide
The VO-DAS system contains several services including VO-DAS server, data node, client, storage server and registry server. The installation is how to deploy these interdependent services into one unified system. More information are included in the “tar.gz” file here (about
- VO-DAS server: There are two kinds of containers, i.e. Globus and Tomcat, in which VO-DAS server can be deployed. For Tomcat, you can download the “tar.gz” file above in which VO-DAS has been deployed. But you can directly use existed VO-DAS server, i.e. http://159.226.169.50:8080.
- Data Node: It is generated by operating commands manually. See more information, please see the website of OGSA-DAI WSRF 2.2 and the related file above. This step will be produced an XML file, i.e. metadata.xml, which contains metadata of datasets in VOTable. Catalog and spectrum data node are provided in VO-DAS system now.
- Registry : The registry is simplified as an XML file in which URI of metadata.xml above has registered.
- Storage Server : FTP server is only supported in VO-DAS system. It is usually specified by user when user want to submit asynchronous query.
- Client: configuring, running and connecting the client to VO-DAS server, then access datasets stored in data nodes through VO-DAS server. you can use three ways to access VO-DAS: graphical, command line and webpage.
If you want to understand more information about the VO-DAS system, please download the system’s source codes “tar.gz” file here (about
FAQ:
1. What are functions of these services and the relationships among them?
VO-DAS system is consisted of VO-DAS server, data node, registry, storage and client. The functions are as follows:
VO-DAS Server: It is the core part and its aims are to manage, parse and control some tasks submitted by user.
Data Node: It mainly encapsulates data resources, which can be directly accessed by VO-DAS Server.
Registry: it is simply considered as a container which contains some URIs of data nodes .
Storage: It is used to store data retrieved by user. You can choose any storage server that supports FTP.
Client: It is a program that controls a display for the user and that allows the user to interact with the system.
The relationships are as follows.
2. Why you design three different clients?
Because different clients can adapt for the different requirements of astronomers. GUI is a full Graphic User Interface, so It is frendly and simple for user to access VO-DAS. command line is full commands to visit VO-DAS, so you can use it to do more complex tasks and to develop softwares based on it. Webpage is an easiest way for user, as it do not require to configure environment at all.
3. Whether these services can be deployed on one machine?
Yes, you can deploy them to the same machine. You can also do it on separated machine.
4. Why do I always not successfully setup or deploy?
It is difficult for you if you do it in the first time.
5. How to submit tasks to VO-DAS?
For graphic and command line user, you have to edit ADQL and submit it to server; for webpage user, only fill some parameters and submit it.
6. What is to access VO-DAS steps?
Before you access the VO-DAS, you have to type the server IP and port and make the client connect to VO-DAS server successfully. Second, edit ADQL (for graphic and command line) or fill parameters (for webpage) and submit it to the server; then the server begin to process these tasks. Now you can wait a minute or check what are statuses of these tasks. After these tasks are completed to process , VO-DAS returns the result datasets for synchronous query or you can download the datasets from the storage server for asynchronous query.
7. What is difference between synchronous query and asynchronous query?
Synchronous query and asynchronous query are supportted in VO-DAS system:
- Synchronous query is that user can not simultaneously submit query jobs, and user has to submit job to server till the result datasets of last task are returned. It meets small volume data query.
- Asynchronous query allows user to submit a number of consecutive jobs without waiting for the result of query. It meets big volume data query.
Future Plans
- As VO-DAS system is improving, more information will be added or updated.
Developers include Chao LIU, Haijun TIAN, Dan GAO, Yang YANG , Yong LU and Chenzhou CUI. Suggestion and comment are sincerely welcome, please send to Chenzhou Cui and Yang YANG.
© 2009, China-VO
