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VO Standards and Protocols XML VOTable UCD ConeSearch Roy Williams California Institute of Technology NVO co-director.

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Presentation on theme: "VO Standards and Protocols XML VOTable UCD ConeSearch Roy Williams California Institute of Technology NVO co-director."— Presentation transcript:

1 VO Standards and Protocols XML VOTable UCD ConeSearch Roy Williams California Institute of Technology NVO co-director

2 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 and answer queries like this: Find all memos from April 1723

3 XML Documents and data Human readable, editable, mailable Schema constrains structure -- can encode data models Can be transformed (XSLT) -- other xml -- html/pdf/excel etc Tools Parsers in Java, C, C++, Perl, Python,... Browsers and editors XML databases Binding to make API For serialization, mediation, brokers

4 XML for science XML is a comfortable vehicle for our metadata and data models But the real challenge is: To define NVO-specific data objects And how they are used We need consensus more than either software or hardware VOTable VOResource services -- WSDL

5 XML example (no schema) The Cambridge Star Atlas Wil Tirion Cambridge UP Parallel Computing Works! Geoffrey C. Fox Roy D. Williams Paul C. Messina Morgan Kaufmann

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

7 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

8 Book.xsd = Xml-Schema Definition XML Schema

9 Book.xsd = Xml-Schema Definition XSchema All XML schemas have schema as the root element

10 Catalog is a sequence of books XSchema Default Namespace declaration: all these come from this standard namespace

11 Book.xsd = Xml-Schema Definition XSchema This namespace is defined here & abbreviated as "cat" This element comes from the namespace called cat Book element defined here

12 Namespace Content uri://BookCatalogue can be abbreviated as "cat" Here: The cat namespace contains: BookCatalogue Book Title Author ISBN Date Publisher

13 XML example (with schema)

14 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

15 Sample VOTable This parameter is designed to store the observer's name Some bright stars Procyon Vega

16 Table Cell scalar arrays variable length arrays etc boolean bit unsignedByte short int long char unicodeChar float double floatComplex doubleComplex Primitives follows FITS binary table does NOT follow XML schema

17 VOTable is Flexy eg Table of images UCD="meta.code.mime; image.jpeg" datatype="unsignedByte" arraysize="*" eg Table of URL links UCD=meta.ref.url" datatype="char" arraysize="*"

18 VOTable Schema (xsd)

19 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

20 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 binary data allows streaming, parallelism

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

22 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

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

24 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

25 Hierarchy New feature: GROUP

26 Astronomical Data Image –Standard file format: FITS Standardized c.1980 Keyword-value dictionary + binary block Catalog –Derived from image Connected set of bright pixels –Table of stars –Standard format: VOTable Standardized 2002 XML with remote binary Spectrum

27 XSLT Example Output from the messier catalog at Output from messier Catalog Server Messier Number Right Ascension J ' Globular Cluster Canes Venatici M3 is one of more heavily studied globular clusters due to its position in the galaxy, putting it far from interstellar absorbtion. More than 200 variable stars have been observed out of a total of near 50,000. Being one of the brightest clusters, M3 is

28 XSLT Result this table is the result of a conesearch

29 XSLT Program Data

30 Binding to make a Parser for(int i=0; i

31 Unified Content Descriptor UCD is a semantic type phot.mag;em.opt.B Integrated total blue magnitude src.orbital.eccentricityOrbital eccentricity stat.medianStatistics Median Value Base + Specifiers eg error in default right ascension –stat.error; pos.eq.ra; meta.main First word is "type" "what kind of thing is this?" How do we add a stat.error to another?

32 Unified Content Descriptor UCD has services Natural Language Description Find best UCD –Search in NLD Matching functions –if I want pos.eq.ra, is stat.error;pos.eq.ra correct? What about Ontology???

33 Some UCD S stat Statistical parameters Q stat.Fourier Fourier coefficient Q stat.Fourier.amplitude Amplitude Fourier coefficient P stat.covariance Covariance between two parameters P stat.error Statistical error P stat.error.sys Systematic error Q Fit Q Chi2 Q Degrees of freedom Q Goodness or significance of fit Q Observed minus computed Q Parameter of fit Q Residual fit Q stat.likelihood Likelihood S stat.max Maximum or upper limit S stat.mean Mean, average value S stat.median Median value S stat.min Minimum or lowest limit

34 Some UCD S phot Photometry Q phot.calib Photometric calibration Q phot.color Color index or magnitude difference Q phot.color.Cous Color index in Cousins system Q phot.color.Gen Color index in Geneva system Q phot.color.Gunn Color index in Gunn system Q phot.color.JHN Color index in Johnson 65+ system S meta Metadata P meta.bib Bibliographic reference P Author name P meta.bib.bibcode Bibcode P meta.bib.ivo IVOA identifier ivo:// P meta.bib.fig Figure in a paper P meta.bib.journal Journal name P Page number P meta.bib.volume Volume number P meta.code Code or flag P meta.code.class Classification code

35 Cone Search First VO standard service Input: RA, DEC, SR must be present –decimal degrees J2000 Output: VOTable of sky-located data records –must have columns with UCDs: POS_EQ_RA_MAIN, POS_EQ_DEC_MAIN, ID_MAIN RA=300 DEC=25 SR=0.1 IDRADECxyz Request Response

36 Cone Searches in a VO Registry

37 Result of Cone Search RA Dec ID

38 Cone Search + Density Probe Cone Search Density Probe baseURL Spacing Search radius interoperating NVO-compliant services! Federation of Multiple Services

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