IVOA Interoperalibity 2003 1

JVO Query Language

Naoki Yasuda (NAOJ/Japanese VO)

IVOA Interoperalibity 2003 2

Basic Functions of JVOQL

• Query and retrieve required data– Describe query condition– Describe what to retrieve– Describe analyses on retrieved data

• Federate distributed databases– Describe queries for multi databases in one unit

• Federate catalogs (tables) and images– Need not to discriminate catalogs and images

IVOA Interoperalibity 2003 3

Requirement for JVOQL

• Platform independent– VO will be constructed as heterogeneous

system– Query must be transferable among systems

• Sufficient to describe astronomical queries– QL must describe what astronomers want to do

• Easy to understand for human and machine– Necessary for debugging and programming

IVOA Interoperalibity 2003 4

Format of JVOQL

• JVOQL adopted SQL as a base language– SQL is a well-defined query language optimized for

relational database– SQL is easy to understand for human and machine– Backend queries can be done by DBMS

• Astronomy specific functions are defined as extensions for SQL– SQL is not sufficient enough for astronomical queries

• XMATCH (Cross Matching)• AREA (Image cutout / Celestial area limit)

IVOA Interoperalibity 2003 5

Extension 1 : Cross-Matching

• Astronomical objects will be identified mainly based on its celestial position (and distance from the earth).

• Distributed databases can be related through celestial positions.

• Similar to ‘join’ in SQL– where A.id = B.id

– where XMATCH(A, B) < 3 arcsec

IVOA Interoperalibity 2003 6

XMATCH

• XMATCH(A, B, !C, …) < 3 arcsec– Select objects whose celestial positions in catal

og A and catalog B coincide within the tolerance of 3 arcsec but not found in catalog C.

Catalog A Catalog B Catalog C

IVOA Interoperalibity 2003 7

Extension 2 : Image cutout

• In most cases, astronomers request images associated with objects selected from catalogs.– Cutout area will be defined as celestial area.

• Celestial area definition can be used to limit searching celestial area.

• Image cutout can be easily expressed like SQL– select A.ra, A.dec, A.BOX(POINT(A.ra, A.dec, J2000), 3 arcmin, 3 arcmin)

IVOA Interoperalibity 2003 8

AREA

• POINT(long, lat, coord) will define a point on the celestial sphere.– coord could be J2000, B1950, GAL, …

• AREA will be defined based on POINT– BOX(POINT(…), width, height[, PA])CIRCLE(POINT(…), radius)OVAL(POINT(…), rad1, rad2[, PA])TRIANGLE(POINT(…), POINT(…), POINT(…))

IVOA Interoperalibity 2003 9

Sample Querycreate view myEROtable asselect s.ra, s.dec, s.Rmag, t.Kmag, sr.BOX(POINT(s.ra, s.dec, J2000), 1 arcmin, 1 arcmin) as Rimage, tk.BOX(POINT(s.ra, s.dec, J2000), 1 arcmin, 1 arcmin) as Kimagefrom SUBARU s, 2MASS t, SUBARU.R sr, 2MASS.K tkwhere XMATCH(s,t) < 3 arcsec and (s.Rmag-t.Kmag) > 6 mag and BOX(POINT(201.0 deg, 27.4 deg, J2000), 1 deg, 1 deg)

IVOA Interoperalibity 2003 10

Sample Querycreate view myEROtable asselect s.ra, s.dec, s.Rmag, t.Kmag, sr.BOX(POINT(s.ra, s.dec, J2000), 1 arcmin, 1 arcmin) as Rimage, tk.BOX(POINT(s.ra, s.dec, J2000), 1 arcmin, 1 arcmin) as Kimagefrom SUBARU s, 2MASS t, SUBARU.R sr, 2MASS.K tkwhere XMATCH(s,t) < 3 arcsec and (s.Rmag-t.Kmag) > 6 mag and BOX(POINT(201.0 deg, 27.4 deg, J2000), 1 deg, 1 deg)

common constraint

multiple DB constraints

IVOA Interoperalibity 2003 11

select count(*)from SUBARU swhere BOX(POINT(201.0, 27.4, J2000), 1.0, 1.0)

select count(*)from 2MASS tWhere BOX(POINT(201.0, 27.4, J2000), 1.0, 1.0)

count 1

count 2

First count the number of objects which satisfies common constraints

According to the counts, server access sequence will determined

count 1 count 2>

2MASS

SUBARU

count 1 count 2<

2MASS

SUBARU

IVOA Interoperalibity 2003 12

select s.ra, s.dec, s.Rmagfrom SUBARU swhere BOX(POINT(201.0, 27.4, J2000), 1.0, 1.0)

select t.Kmagfrom 2MASS twhere XMATCH(s,t) < 3 arcsec and (s.Rmag-t.Kmag) > 6 mag

select sr.BOX(POINT(s.ra, s.dec, J2000),…) as Rimagefrom SUBARU.R sr

select tk.BOX(POINT(s.ra, s.dec, J2000),…) as Kimagefrom 2MASS.K tk

Output Table A

Output Table B

Output Table C

Result Table

IVOA Interoperalibity 2003 13

Extension of AREA

• Usual queries are for catalogs• There is a need for query for area like

– Search for area where V band, I band, and K band observations are available.

– Search for area where observed in B band more than 3 times and their intervals are more than 1 month.

– …

• These queries will expand the usefulness of astronomical data archives.

IVOA Interoperalibity 2003 14

Sample Queries

select s.a, t.a, ...from SUBARU.R s, 2MASS.K t, ...where (s.AREA() OVERLAP t.AREA()) as a

select x.a, y.afrom SUBARU.B x, SUBARU.B ywhere (DIFF(x.obs_date, Y.obs_date) > 30 days) and (s.AREA() OVERLAP t.AREA())) as a

IVOA Interoperalibity 2003 15

s.AREA() t.AREA()

AREA info

OVERLAP

cutout request

Div

ide

into

pi

eces

s ta1a2a3