1. Google Sky

2. VO-DAS, Uniform Resolution for Astronomical Data Access
Chenzhou CUI
Chinese Virtual Observatory Project
National Astronomical Observatory of China

3. Contents Brief introduction of Virtual Observatory
Data access in Virtual Observatory
VO-DAS architecture
VO-DAS use cases
Prospects and concerns
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4. VO concept
Virtual Observatory (VO) is a data-intensively online astronomical research and education environment, taking advantages of advanced information technologies to achieve seamless, global access to astronomical information.
The power of the World Wide Web is its transparency. It is as if all the documents in the world are inside your PC. The idea of the Virtual Observatory is to achieve the same transparency for astronomical data and other related information (Quinn et al. 2004).
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5. IVOA in Growth International Virtual Observatory Alliance (IVOA)
formed in June 2002
with a mission to facilitate the international coordination and collaboration necessary for the development and deployment of the tools, systems and organizational structures necessary to enable the international utilization of astronomical archives as an integrated and interoperating virtual observatory.
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6. IVO, Global Astronomy GRID
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7. Data Access in the VO
The task of the IVOA Data Access working groups is to define and formulate VO standards for remote data access.
Client data analysis software will use these services to access data via the VO framework; data providers will implement these services to publish data to the VO.
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8. Online Astronomical Resources
Catalogs (tabular data, database tables)
CDS VizieR, SDSS DAS, ...
Image archives
NASA Centers, CDS Aladin, SDSS, DSS, …
Spectrum archives
SDSS, LAMOST, …
Bibliographic archives
ADS, arXiv::astro-ph, …
Information services
Software, services, etc
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9. IVOA Data Access Specifications
Simple Cone Search
Simple Image Access
Simple Spectral Access
IVOA Astronomical Data Query Language
IVOA SkyNode Interface
VOTable Format Specification
VOSpace service specification …
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10. VO Data Access System (VO-DAS)
An OGSA-DAI based service system to provide uniform access to astronomy data, including catalogs, images and spectra.
Goals of VO-DAS
Supporting high volume data query
Interlinking distributed and heterogeneous archives
catalogs, images, spectrums
Providing a software that works for astronomers
OGSA-DAI Supported Asynchronous Data Access Service
OGSA-DAI is a middleware product which supports the exposure of data resources, such as relational or XML databases, on to grids.
Work with Globus Toolkit 4
WSRF interface
Good wrapper for variant databases
Asynchronous query supported
Available for large dataset
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11. VO-DAS Architecture Interfaces VO-DAS Server VO-DAS Server DataNode
WSRF based web service
Integrates OGSA-DAI services
Job controlling and monitoring
DataNode
OGSA-DAI wrapped data resources
Interfaces
Resource Metadata Interface
Data Query Interface
Data Delivery Interface
Data Analysis Interface
Management Interface
Data Node
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12. CANS 2007, Aug , 2007, Xi'an
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13. VO-DAS Use Cases Query Workflow Synchronous Query Asynchronous Query
Asynchronous Query on multiple DataNodes
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14. Asynchronous Query on Multiple DataNodes
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15. Interoperability Resource Registry: VO Registry
Archive Integration: OGSA-DAI WSRF
Query Language: ADQL and extension
Data Format: VOTable, ASCII, CSV, FITS etc.
Storage: FTP, (VOSpace?)‏
Interfaces: ConeSearch, SIA, SSA, etc.

16. Status An Alpha version of VO-DAS was ready
Simple ADQL access by a GUI java client
ConeSearch and XMatch between multiple OGSA-DAI services
VOTable, ASCII, CSV data format
Simple job controlling and monitoring
FTP storage server
Automatic resource discovery on NVO Registry
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17. Performance High Volume Data Query Test Frequently Data Query Test
Long time to query and retrieve big data file
Frequently Data Query Test
Multiple user simultaneously query
A user frequently access data from server
Conclusion
A million rows can be handled successfully
Depend on memory size
It is not stable when simultaneously query (high loaded case)
Reason: OGSA-DAI’s defect? Or database problem?
It is complicated to handle failure
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18. Science Demo
Galaxy red shift
Galactic Tidal Stream

19. Future Work Short Term Long Term Document and Q&A
Image and spectra support
A stable system
Used by astronomers in a small community
Long Term
VO-DAS + VOSpace?
VO-DAS + VO applications?
VO-DAS + Advanced Workflow?
Document and Q&A
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20. Prospects and Concerns
HXMT
LAMOST
New projects
Data resources
Requirements
Hard time for GRID
Non-technical obstacles
Limited funding for
Manpower
Hardware, esp. data storage
Bandwidth
Isolated management
Coordination is time consuming
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21. ? Q & A Thank You www. .org CANS 2007, Aug. 25-26, 2007, Xi'an
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