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

Contents Brief introduction of Virtual Observatory Data access in Virtual Observatory VO-DAS architecture VO-DAS use cases Prospects and concerns CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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). CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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. CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

IVO, Global Astronomy GRID CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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. CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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 CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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 … CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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 CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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 CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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VO-DAS Use Cases Query Workflow Synchronous Query Asynchronous Query Asynchronous Query on multiple DataNodes CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

Asynchronous Query on Multiple DataNodes CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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.

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 CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

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 CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

Science Demo Galaxy red shift Galactic Tidal Stream

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 CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

Prospects and Concerns 2.4m@LiJiang 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 50m@Miyun CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9

? Q & A Thank You www. .org CANS 2007, Aug. 25-26, 2007, Xi'an 2019/4/9