Aus-VO Workshop 2003

International Virtual Observatory Alliance effort on

Virtual Observatory Query Language

Naoki Yasuda (JVO),

VOQL WG

Aus-VO Workshop 2003

VOQL Working Group

• Chair : Masatoshi Ohishi (JVO)William O'Mullane, Tamas Budavari, Vivek Haridas, Nolan Li, Tanu Malik , Alex Szalay (NVO, JHU)Martin Hill, Tony Linde, Bob Mann, Clive Page (AstroGrid)Jim Gray (Microsoft)Yoshihiko Mizumoto, Naoki Yasuda (JVO)have contributed.

Aus-VO Workshop 2003

Brief History

• Jan 2003 at Seattle : First IVOA Meeting Start WG

• May 2003 at Cambridge : IVOA Interoperability Meeting Agreed on ADQL and SkyNode concept

• Jul 2003 : First Working Draft• Discussions on mailing list have been continued.• Oct 2003 at Strasbourg :

IVOA Interoperability Meeting More detailed discussion

• Nov 2003 : Version 0.6 Working Draft is available

Aus-VO Workshop 2003

Architecture

Aus-VO Workshop 2003

Architecture Description

• Astronomical Data Query Language (ADQL) is an SQL like language but passed as an XML document.

• SkyNodes have standard interface and will accept ADQL and return the query result as VOTable.

• SkyQL have the same semantics as ADQL but the syntax would be an SQL like string rather than XML.

• VOQL is an ambitious language at a higher level than ADQL.

Aus-VO Workshop 2003

3 Layers of VOQL

Aus-VO Workshop 2003

ADQL and SkyQL

• Many astronomical data are tabular data and they are stored in relational database. SQL as a first step

• The only SQL command allowed in ADQL is a “select”.Additional predicates are Region and XMatch.XMatch is supported in Full SkyNode.

• See the XSD for complete structure of ADQL.

Aus-VO Workshop 2003

Select t.*, b.* From Tab t, Bob b Where t.g <> b.g and Region('Circle J2000 12.5 23.0 5.')

<?xml version="1.0" encoding="utf-16"?><Select xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Selection> <ExprSelectionItem> <ColumnExpr> <AllColumnReference> <TableName>t</TableName> </AllColumnReference> </ColumnExpr> </ExprSelectionItem> <ExprSelectionItem> <ColumnExpr> <AllColumnReference> <TableName>b</TableName> </AllColumnReference> </ColumnExpr> </ExprSelectionItem> </Selection> <TableClause> <FromClause> <TableReference> <Table> <Name>Tab</Name> <AliasName>t</AliasName> </Table> <Table> <Name>Bob</Name> <AliasName>b</AliasName> </Table> </TableReference> </FromClause> <WhereClause> <IntersectionSearch> <FirstCondition xsi:type="PredicateSearch"> <ComparisonPred> <FirstExpr xsi:type="ColumnExpr"> <SingleColumnReference> <TableName>t</TableName> <Name>g</Name> </SingleColumnReference> </FirstExpr> <Compare>&lt;&gt;</Compare> <SecondExpr xsi:type="ColumnExpr"> <SingleColumnReference> <TableName>b</TableName> <Name>g</Name> </SingleColumnReference> </SecondExpr> </ComparisonPred> </FirstCondition> <SecondCondition xsi:type="RegionSearch"> <Circle xmlns:q1="urn:nvo-region" xsi:type="q1:circleType"> <q1:Center> <Pos2Vector xmlns="urn:nvo-coords"> <Name>Ra Dec</Name> <CoordValue> <Value> <double>12.5</double> <double>23</double> </Value> </CoordValue> </Pos2Vector> </q1:Center> <q1:Radius>5</q1:Radius> </Circle> </SecondCondition> </IntersectionSearch> </WhereClause> </TableClause></Select>

SkyQL vs ADQL

We need SkyQL as a human readable expression.

Aus-VO Workshop 2003

SkyNode

• All data servers joining the IVO would implement a standard IVOA SkyNode Interface based on Web Services.

• All VO WebServices shall implement the “MetaData” port.

• All VO WebServices shall implement the “Heartbeat” port.

Aus-VO Workshop 2003

Basic / Full SkyNode

Feature Basic SkyNode Full SkyNode Optional

ADQL – circle X X

Functions X X

XMatch X

QueryCost X

Takes exec plan X

Footprint – Region intersect X

MYDB X

Authentication – must have with MYDB

X

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Basic SkyNode Interface

//Return RSM compliant VOResourcepublic VOResource MetaData();

//Return a list of all tables that may be used from this node. public string[] Tables();

//Return ucd, name, unit, type for each column of table public MetaColumn[] Columns(string table);

//Return available query result formats, VOTable, DataSet, ASCII public string[] Formats();

//Return available functionspublic MetaFunctions[] Functions();

//Return the result of executing ADQL query in requested format public VOResult PerformQuery(Select query, string format);

Aus-VO Workshop 2003

Full SkyNode Interface

//Returns object density per square degree for a given criteria.public float QueryCost(Select query);

//Return Cross matched objects according to Query and input Tablespublic VOResult XMatch(Select select, VOTABLE[] votables);

// Return result of executing an ExecPlan, format specified in planpublic VOResult ExecutePlan(ExecPlan plan);

//Return region of intersection between given region and this SkyNodepublic Region Footprint(Region region);

Aus-VO Workshop 2003

Open SkyQuery Portal

• Portal should not be in this specification, but some description will help how to use SkyNodes.

• Open SkyQuery Portal will enable the following query select s.ra, s.dec, s.r, s.i, s.g, s.objid, p.* from SDSS:PhotoObj s, Twomass:Photo t,First:Photo f, SDSS:Spectro p, IVOA:MyDB.MyObjList m where XMatch (s,t,f,m) < 3 and Region(‘Circle Cartesian 0.7 0.2 -0.1 0.02’) and s.objid=p.objid and s.r<15 and abs(s.i-t.j_m)<2

• Open SkyQuery Portal is open version of SkyQuery developed at JHU based on Microsoft .NET technology.

• Currently Open SkyQuery Portal will use only Full SkyNodes.

Aus-VO Workshop 2003

Discussions

• How to use Unified Content Descriptors?UCDs will hide raw column names.UCDs are not unique.

• XMatch algorisms?User customized XMatch.

• XMatch vs Neighboring SearchSomeone need all possible corresponding objects.

Aus-VO Workshop 2003

Summary

• ADQL and SkyNode architecture is adopted in VOQL WG.

ADQL is SQL like language.SkyNode is WebService interface.

• Specifications of ADQL and SkyNode are almost finalized (Jan 2004).

• Full XML-baed VOQL (SkyXQuery) will be available in a few years.

• See details on http://www.ivoa.net/twiki/bin/view/IVOA/IvoaVOQL