an International Virtual Observatory data exchange format VOTable Roy Williams François Ochsenbein Clive Davenhall Daniel Durand Pierre Fernique David Giaretta Robert Hanisch Tom McGlynn Alex Szalay Andreas Wicenec

XML: Structured Information Antonio Stadivarius Domenico Scarlatti Io bisogno una appartamento acoglienti a Cremona … 4/13/23 April 13, iv.1723 Separation of structure from presentation The computer can read the document: Find all memos from April 1723

VOTable Full metadata representation Hierarchy of RESOURCEs containing PARAMs and TABLEs UCD (unified content descriptor) –a has unit meter –a has UCD ORBIT_SIZE_SMAJ (Semi-major axis of the orbit ) Can reference remote and/or binary streams Table can be –Pure XML –"Simple Binary" –FITS Binary Table

VOTable Parentage Astrores XML format for tables Developed at CDS Strasbourg Presented at ADASS 1999 Vizier implementation XSIL XML format for Tables and Arrays Developed at LIGO Caltech 2000 Extensible through Type-Class dynamic loading Java parsing, browsing, editing Matlab interface

Sample VOTable This parameter is designed to store the observer's name Some bright stars <FIELD name="RA" ucd="POS_EQ_RA" ref="myJ2000" unit="deg" datatype="float" precision="F3" width="7"/> <FIELD name="Dec" ucd="POS_EQ_DEC" ref="myJ2000" unit="deg" datatype="float" precision="F3" width="7"/> Procyon Vega <STREAM href="ftp://server.com/mydata.fits" expires=" " actuate="onRequest"/>

Table Cell scalar arrays variable length arrays etc boolean bit unsignedByte short int long char unicodeChar float double floatComplex doubleComplex Primitives

VOTable is Flexy eg Table of images UCD="JPEG_IMAGE" datatype="unsignedByte" arraysize="*" eg Table of URL links UCD=DATA_LINK" datatype="char" arraysize="*"

VOTable Schema (xsd)

Table Data Model Metadata Class definition for Row FIELD –data type –semantic type Data Each Row is a list of Cells Each Cell is an array of Primitives –may be variable length

Table Data Layout All metadata first –small, complex, XML Class definition for table record + params, description, etc etc Then data –(may be) large, remote –XML | binary | FITS Instantiations of table record All records MUST have same format

Param Data Model Param is Table with one cell Like a FIELD value But with a value attribute

Primitives All have fixed binary length Same as FITS primitives Except Unicode datatype Meaning FIT S Bytes "boolean"Logical"L""L"1 "bit"Bit"X""X"* "unsignedByte"Byte (0 to 255)"B""B"1 "short"Short Integer"I""I"2 "int"Integer"J""J"4 "long"Long integer"K""K"8 "char"ASCII Character"A""A"1 "unicodeChar"Unicode Character 2 "float"Floating point"E""E"4 "double"Double"D""D"8 "floatComplex"Float Complex"C""C"8 "doubleComplex"Double Complex"M""M"16

Multidimensional Array Cell A table cell can have lots of Primitives Example: WCS parameters are arrays – Example: up to 10 images, each 64x64 –

Hierarchy A VOTable contains RESOURCES –RESOURCE can contain: TABLE RESOURCE etc Usage example Many observations in the file, –each is a RESOURCE Each observation is –Parameters –Calibration table –Raw data table

Hierarchy New feature: GROUP

Unified Content Descriptors UCD is a semantic type PHOT.INT-MAG.B Integrated total blue magnitude ORBIT.ECCENTRICITYOrbital eccentricity STAT.MEDIANStatistics Median Value INST.QEDetector's Quantum Efficiency Can be resolved by web service –to description, examples, etc Base + Specifiers eg error in default right ascension POS.EQ.RA, MAIN, ERROR

VOTable Friends XMLBinary Streaming TableDatacubeSemantics VOTable BinX MS Dataset HDF XDF Some self-describing file formats

XML Parsing SAX : Event-Based Handlers for StartElement, Text, EndElement, etc. Found element BookCatalogue Found element Book Found Element Title Found Text The Cambridge Star Atlas Found End Element Title ….

Parsing DOM : Document Object Model Returns a tree-like Document object with data attached BookCatalogue Book Title ISBNParallel Computing Works! Cambridge Star Atlas Title Author Wil Tirion

Binding to make a Parser for(int i=0; i<table.getFieldCount(); i++){ Field field = (Field)table.getFieldAt(i); String u = field.getUcd(); if(u != null && u.equals("POS_EQ_RA_MAIN")) System.out.println("Field " + i + " is for RA"); } From the Schema an API and library is generated JAXB Breeze Castor This is JAVOT (Caltech)

VOTable Software Treeview from UK-VO

VOTable Software VOPlot from India-VO

VOTable Software VOTool from US-VO

VOTable software Mirage from Bell Labs