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Datatypes for OGSA Dr Martin Westhead Principal Consultant, EPCC Telephone: +44 131 650 5958

Datatypes for OGSA Dr Martin Westhead Principal Consultant, EPCC Telephone: +44 131 650 5958 Fax: +44 131 650 6555 Email: M.Westhead@epcc.ed.ac.uk. Overview. Uses of XML Basic types Complex types Binary File Description Discussion – feedback. Uses of XML. Two distinct areas:

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Datatypes for OGSA Dr Martin Westhead Principal Consultant, EPCC Telephone: +44 131 650 5958

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  1. Datatypes for OGSA • Dr Martin Westhead • Principal Consultant, EPCC • Telephone: +44 131 650 5958 • Fax: +44 131 650 6555 • Email: M.Westhead@epcc.ed.ac.uk

  2. Overview • Uses of XML • Basic types • Complex types • Binary File Description • Discussion – feedback.

  3. Uses of XML • Two distinct areas: • Meta data – input values, algorithm choices etc. • Real datasets – large scale datasets • More interest in (1) – natural use of XML • Some interest in (2) but: • Some issues with basic types (also a problem for 1) • Modifying apps to read/write XML hassle • XML layout may be inconvenient (e.g. arrays) • Why bother? • Proposed work • Fixes for basic types • XML schema for describing large binary files

  4. “XML Schema Part 2: Datatypes” http://www.w3.org/TR/xmlschema-2/ Floating point: Decimal – arbitrary precision decimal Float – IEEE 754 (32 bit) Double – IEEE 754 (64 bit) Not defined: Quadruple ?? (128 bit) Integers long int short byte nonPositiveInteger negativeInteger nonNegativeInteger positiveInteger unsignedLong unsignedInt unsignedShort unsignedByte Basic Types I

  5. Basic Types II • Complex numbers • Proposed W3C standard: • http://www.w3.org/2001/03/XMLSchema/TypeLibrary-nn-math.xsd • Uses decimals only • Need floats/doubles • Alternative standard: • http://www.posc.org/ebiz/pefxml/bdoc/dt_complex.html • Proposal • Aim to contribute to W3C complex standard

  6. Complex Types • Arrays • W3C proposal • http://www.w3.org/2001/03/XMLSchema/TypeLibrary-nn-array.xsd • Multidimensional array as a tree of lists (vectors) • Polymorphic • Sparse array supported in SOAP • http://www.w3.org/TR/SOAP/ (section 5.4.2.2) • Many alternative representations possible • What else? • Sets, bags, graphs, meshes?

  7. Binary File Description • Part of metadata • Canonical description of output • Enables web services for: • Conversion • Returning part of data (e.g. slice of array) • Different levels of description • Accessing numbers • Big/little endian • Precision • Offset • Record separators…etc • Higher level structure • Array dimensionality/size • Variable names

  8. Discussion • Feedback? • What do you/your users want to use XML for? • Value of standard binary description?

  9. NeSC registry • XML schema references (Yahoo!) • XML schema mirrors • UDDI registry of eScience Grid Services

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