Astronomical Data Analysis Software and Systems XIV
ASP Conference Series, Vol. XXX, 2005
P. L. Shopbell, M. C. Britton, and R. Ebert, eds.

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Japanese Virtual Observatory (JVO) prototype 2
Masahiro TANAKA, Yuji SHIRASAKI, Satoshi HONDA, Yoshihiko
MIZUMOTO, Masatoshi OHISHINational Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka,
Tokyo 181-8588, Japan
Naoki YASUDA
Institute for Cosmic Ray Research, University of Tokyo, 5-1-5
Kashiwanoha, Kashiwa, Chiba, 277-8582, Japan
Yoshifumi MASUNAGA
Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo, 112-8610, Japan
Yasuhide ISHIHARA, Katsumi ABE, Jumpei TSUTSUMI
Fujitsu Ltd., 1-9-3 Nakase, Mihama, Chiba, 261-8588, Japan
Hiroyuki NAKAMOTO, Yuusuke KOBAYASHI, Tokuo YOSHIDA,Yasuhiro MORITA
Systems Engineering Consultants Co. Ltd., 9-8 Sakuragaoka, Shibuya,Tokyo, 150-0031, Japan
Abstract. We describe the architecture of the Japanese Virtual Observatory (JVO) prototype system version 2. JVO aims at seamless accessto astronomical data archives stored in distributed data servers as well
as data analysis environment. For this purpose, it is important to establish a framework for access to remote servers, including remote procedure
calls (RPCs) and data transfer. A data request for distributed databaseis described in the JVO Query Language. The JVO system parses thequery language, decomposes it into individual remote procedures such as
retrieval of catalog, image and spectrum and cross matching, and generate a work flow. Based on this work flow, remote procedures are called.
For RPCs of JVO prototype system 1, we employed Globus toolkit 2(GT2). However, latency time of GT2 RPCs was too long for successive short-time jobs. Therefore, we employed Globus toolkit 3 (GT3)for JVO prototype system 2. As a result, we find that Grid Service in
GT3 improves performance of RPC. In addition to Grid Service, Reliable File Transfer (RFT) is used for efficient data transfer. Astronomical
data stored in distributed servers are discovered through a registry serverwhich provides metadata discussed in the IVOA registry working groupand is built using a XML database.

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1.

Introduction

JVO1 is a project of National Astronomical Observatory of Japan. The objectiveof JVO is to provide astronomers with seamless access to huge data archives
produced with astronomical telesopes of Japan such as Subaru telescope. JVO
is also participating in IVOA2 (International Virtual Observatory Alliance) todiscuss standard protocols for the purpose of accessibility to astronomical dataarchives from/to the world.
We have developed JVO prototypes iteratively; the JVO prototype version 1(Proto 1) was developed in 2002, the prototype version 2 (Proto 2) in 2003, andthe prototype 3 is under development. In the course of Proto 1 development,
we defined JVO Query Language (JVOQL; Mizumoto et al. 2003) based on theSQL through extending cross match and image retrieval functionalities. And
we constructed Proto 1 system which consists of distributed database and analysis servers federated through Grid (Ohishi et al. 2004, Shirasaki et al. 2004).
As a result, we confirmed that Proto 1 accepts properly query commands described in JVOQL, and actually operates as a distributed database. However,
we found several problems, including the performance of remote execution anddata discovery. These issues are improved in JVO Proto 2 as described in thispaper.
2.

System Design

The system configuration of JVO Proto 2 is shown in Figure 1, which is basically same as Proto 1. Technical components adopted for JVO prototypes arecompared in Table 1, and described in the following sections.
Table 1.
Technical components adopted for JVO prototypes
Registry
Grid middleware remote execution data transfer
Proto 1 UDDI
Globus v.2
globus-job-run
GridFTP
Proto 2 XML DB Globus v.3
Grid Service
RFT & SFS

3.

Execution Controller

User’s query commands described by JVOQL are processed by the Controller.
The Controller cooperates with the following subcomponents; JVOQL Parser,Scheduler and Executer. These components are written in Java language
and installed in the portal server. The JVOQL parser analyzes the syntax ofthe JVOQL command and decomposes it into query elements. The Java code
to parse the syntax of the JVOQL is generated with JavaCC (Java CompilerCompiler). The Scheduler receives an output of the parser, and generates awork flow which consists of job elements for individual servers. Based on this1

http://jvo.nao.ac.jp/2

http://www.ivoa.net/

Japanese Virtual Observatory (JVO) prototype 2

Figure 1.

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JVO system configuration

work flow, the Controller calls the Executer which calls procedures on remotemachines.
4.

Data Discovery

When the Controller performs a query for distributed data servers, it is necessary to find the location of the requested data. Such information is retrieved
from a Registry server. For Proto 1, we constructed a registry server using
UDDI (Universal Description, Discovery, and Integration). UDDI is designed tofind services in the Web Services framework, however, UDDI is not necessarily
suitable for search services of complicated astronomical metadata. Therefore,
we redesigned the registry system for Proto 2. The contents of metadata aredefined so as to keep compatibility with the metadata standard proposed in
IVOA. We stored these metadata into an XML database product KAREAREA,
and enabled metadata search by XPath. We plan to use the OAI-PMH (OpenArchives Initiative Protocol for Metadata Harvesting) for exchanging metadata
between data servers and a registry server.
5.

Remote Execution

Standard protocols for remote procedure calls (RPCs) are necessary for federation of astronomical databases distributed all over the world. For this purpose,
we considered to apply standard Grid middleware, Globus Toolkit, developed
by Globus Alliance3 , and investigated its applicability to JVO. We constructed3

http://www.globus.org/

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Proto 1 using Globus Toolkit version 2 (GT2). However, the result showed thatelapsed time to execute a basic JVOQL example was more than 10 minutes(Ohishi et al. 2004). This is probably because the globus-job-run command
used for Proto 1 is not designed for a series of light-weighted, i.e., pseudo-realtimeprocedure calls. To improve the performance, we reimplement RPCs of JVO
Proto 2 using Grid Service introduced in Globus Toolkit 3 (GT3). The Grid
Service is based on the Web Services. After the implementation into Proto 2,
we examined two queries which take 2.3 and 13 seconds as actual processing
times in remote servers, respectively. The result is that elapsed times including
RPCs are 2.8 and 16 seconds, respectively. The measured overhead time is onlyaround 30 ms. Thus the performance of Proto 2 is much improved comparedwith Proto 1. This result shows that Proto 2 system using Grid Service can bea basis of practical virtual observatory systems.
6.

Data Transfer

We employed two data transfer protocols for JVO Proto 2; one is the Reliable
File Transfer (RFT), and the other is the Self-certifying File System (SFS)4 .
The RFT is one of the GT3 services, and it provides interfaces for recoverable
file transfer using the GridFTP protocol. The RFT enables a portal server toissue file copy commands between two remote hosts. This function is useful for
multi-server operation like cross match (XMatch). The SFS is a secure networkfile system over the Internet. We find the SFS does not provide data transfer
service between remote hosts, which is a benefit of the RFT, since SFS serverand client processes cannot coexist on a single machine.
As mentioned above, we adopted Grid Service for remote execution, andRFT and SFS for data transfer. However, the use of different protocols brings
complicated implementation. Furthermore, IVOA standard protocols like SIAP
(Simple Image Access Protocol) are implemented with single protocols like HTTP
or Web Services. Therefore, we are considering to utilize HTTP or Web Servicesfor RPCs and data transfer in the next prototype and operational JVO systems.
Acknowledgments. This work was supported by the JSPS Core-to-Core
Program and Grant-in-aid “Information Science” (15017289 and 16016292) carried out by the Ministry of Education, Culture, Sports, Science and Technologyof Japan.
References
Mizumoto, Y., et al. 2003, in ASP Conf. Ser., Vol. 295, ADASS XII, ed. H. E.
Payne, R. I. Jedrzejewski, & R. N. Hook (San Francisco: ASP), 96
Ohishi, M., et al. 2004, in ASP Conf. Ser., Vol. 314, ADASS XII, ed. F. Ochsenbein, M. Allen, & D. Egret (San Francisco: ASP), 296
Shirasaki, Y., et al. 2004, in ASP Conf. Ser., Vol. 314, ADASS XII, ed. F. Ochsenbein, M. Allen, & D. Egret (San Francisco: ASP), 464

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