  We present the design and implementation of the Japanese Virtual Observatory
(JVO) system. JVO is a portal site to various kinds of astronomical resources
distributed all over the world. We have developed five components for
constructing the portal: (1) registry, (2) data service, (3) workflow system,
(4) data analysis service (5) portal GUI. Registry services are used for
publishing and searching data services in the VO, and they are constructed
using an OAI-PMH metadata harvesting protocol and a SOAP web service protocol
so that VO standard architecture is applied. Data services are developed based
on the Astronomical Data Query Language (ADQL) which is an international VO
standard and an extension of the standard SQL. The toolkit for building the
ADQL-based service is released to the public on the JVO web site. The toolkit
also provides the protocol translation from a Simple Image Access Protocol
(SIAP) to ADQL protocol, so that both the VO standard service can be
constructed using our toolkit. In order to federate the distributed databases
and analysis services, we have designed a workflow language which is described
in XML and developed execution system of the workflow. We have succeeded to
connect to a hundred of data resources of the world as of April 2006. We have
applied this system to the study of QSO environment by federating a QSO
database, a Subaru Suprim-Cam database, and some analysis services such a
SExtractor and HyperZ web services. These experiences are described is this
paper.
