Sept. 2003NVO Team Meeting / Victoria 1

VOQL/ADQL/MYDB for VO

William O’MullaneJohns Hopkins University

THE US NATIONAL VIRTUAL OBSERVATORY

Sept. 2003NVO Team Meeting / Victoria 2

Virtual Observatory Query Language Layers

VOQL3 SkyXQuery

VOQL2 SkyQL

VOQL1 WebServices

future XML-based query language.

SQL-like query language and federation system i.e. combination of SkyQuery , JVOQL and VO standards

Astronomical Data Query Language (ADQL) and VOTABLE to exchange information between machines

Sept. 2003NVO Team Meeting / Victoria 3

Architecture

Clients

VOQL PortalHigh Level Language allowing

seemingly uniform access to services.

VOQLQuery

IVOA SkyNodesLower level ADQL (including regions) and services to Support VOQL.

later End 2003

Tables

MetaData

PerformQuery

Columns

LEV1

Tables

MetaData

PerformQuery

Columns

LEV2

XMatch

Tables

MetaData

PerformQuery

Columns

LEV1

RegistryRegister

Tables

MetaData

PerformQuery

Columns

LEV4

XMatch

ExecPlan

Footprint

Tables

MetaData

PerformQuery

Columns

LEV3

XMatch

ExecPlan

Open SkyQuery PortalUses only Registry, Lev3 and Lev4 SkyNodes.

SkyQuerySkyQueryWebApp

May use Services at any level

SKYQL

ADQL

VOQL

ADQL

ADQL

Sept. 2003NVO Team Meeting / Victoria 4

SkyNode Levels 

Feature LEV1–ADQL

LEV2 – XMATCH

LEV3- SKYNODE

LEV4- SKYNODEAdvanced

Optional

ADQL – circle X X X X

Xmatch   X X X

Performance Query   X X

Takes exec plan   X X

Footprint – Region intersect

  X

MYDB   X

Authentication X

Sept. 2003NVO Team Meeting / Victoria 5

SkyQL and ADQL

• Same semantics different syntax• ADQL - parse tree easy for SkyNodes• SkyQL – textual easy for humans• ADQl Includes Rots regions,

Xmatch,math functions

• Simple parser working both ways(demo)ADQLtoSkyQL SkyQLtoADQL

Sept. 2003NVO Team Meeting / Victoria 6

MYDB – not in v0.4

• local space for data and results– Like astorgrid mysapce

• Requires on node– User Identification– Job tracking/monitoring– Asynchronous execution

• CasJobs does all of this (short demo)– http://skyservice.pha.jhu.edu/devel/casjobs

• Should we try to do this for OpenSkyQuery now?• What about across nodes…

Sept. 2003NVO Team Meeting / Victoria 7

MYDB across Nodes

• Need user identification across nodes– Centralize (not nice technically nor

politically)– How to integrate with exiting mysapce and

MYDB …

• Federate ! (IBM/MS Paper )– Authentication service on each node– User signs up anywhere or uses exisiting id– Accept userids issued by trusted nodes

• Authenticate userid with node it is supposed to be from

Sept. 2003NVO Team Meeting / Victoria 8

Security with federated Auth.

• How secure do we want this?• Should the userid be:

– an encrypted token – just a number

• Do we copy user info to each node so we can have integrity constarins in our db on USERID

Sept. 2003NVO Team Meeting / Victoria 9

MYVOSPACE

Next step is an integration serviceOne stop service

Sept. 2003NVO Team Meeting / Victoria 10

Current Issues for discussion

Since v0.3

Sept. 2003NVO Team Meeting / Victoria 11

Hardcore Levels

• Drop Lev3 Skynode • Require Footprint/Region intersect for

Skynodes.

• Personally – I think we will have nodes without and would rather have a name for them

Sept. 2003NVO Team Meeting / Victoria 12

Interface Issue

Currently PerformQuery returns VOTableVotable performQuery (ADQL query)

M.Hill would like a more general wrapper e.g.IVOAResult performQuery (ADQL query)

Here IVOAResult would be abstract or a wrapper containing VOTable or some pointer to a file.

Would also allow for putting other things in result (region densities Yasuda San has suggested).

Sept. 2003NVO Team Meeting / Victoria 13

Neighbours or XMatch

• Xmatch is a probabilistic matching returning all neighbours taking account of errors.

• B. Mann suggests we should use lowest common denominator which is Neighbors – this would return all objects within a certain distance of each other not using the errors.

Sept. 2003NVO Team Meeting / Victoria 14

Region Specification Issue

Have suggested Region,RefionUrl,RegionXml. Region would take simple strings like ‘Circle j200 810 34.2 0.1’

A.Rots has another suggestion for Region strings which is comprehensive Is this as complex as just using the XML …

Sept. 2003NVO Team Meeting / Victoria 15

A. Rots Region Strings

define CSys = (TimeFrame = (TimeScale='TT') and (TimeRefPosition='TELESCOPE')) and (SpaceFrame = (CoordFrame='ICRS') and (CoordRefPosition='TELESCOPE')) and (SpectralFrame = 'OBSERVATORY') and (CoordFlavor = 'SPHERICAL')define CArea = (TimeInterval = (StartTime=(ISOTime='2000-01-01')) and (StopTime=(ISOTime='2002-12-31'))) and (Region = (Circle = (Center='60.0d,30.0d') and +(Radius='10arcmin')) and (SpectraLinterval = (LoLimit='1GHz') and (HiLimit='2GHz'))define CSpec = (Time = (CoordResolution<='10s')) and (Pos2Vector = (CoordResolution<='10arcsec,10arcsec')) and (Spectrum = (CoordResolution<='50MHz'))

The query:select <SelectList> from <ResourceList> where <WhereClauses> and SearchLocation = (CoordSystem = $CSys and CoordArea = $CArea