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Data formats in e-Science

Data formats in e-Science. Two key requirements Interoperability and Scalability XML is flexible, but verbose Binary formats are compact, but specific e.g. VOTable vs FITS issue in the VO Two possible solutions: BinX from the edikt project at NeSC VX from the School of Informatics.

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Data formats in e-Science

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  1. Data formats in e-Science • Two key requirements • Interoperability and Scalability • XML is flexible, but verbose • Binary formats are compact, but specific • e.g. VOTable vs FITS issue in the VO • Two possible solutions: • BinX from the edikt project at NeSC • VX from the School of Informatics

  2. BinX: Binary in XML • A language: • Uses XML to describe the data types and structures in a binary data file • A library: • For manipulating XML and binary files • BinX files: • SchemaBinX: XML descriptor of binary file • DataBinX: SchemaBinX + data values • BinX will allow you to interact with a binary file as if it were XML – e.g. run XPath queries

  3. Astronomical testbed: format conversion with BinX

  4. …and back again This way is harder, due to ASCII text in FITS header.

  5. More about BinX • Download the BinX code & play with it • See www.edikt.org/binx • After BinX comes DFDL (daffodil ) • Data Format Description Language • Developing through GGF Working Group • BinX might morph into a DFDL implementation • Basic idea behind DFDL: • We can’t have a single data format, but we can have a single way of describing data formats

  6. VX: Vectorizing XML • XML seems especially verbose for data files with simple, repeating structures • e.g. VOTable – lots of <TR>s and <TD>s • Vectorize it: • Decompose the XML document into a skeleton describing the structure and vectors containing data values

  7. Example: bibliography in XML

  8. Astronomical VX application • Export the PhotoObj Table from the SDSS EDR database into VOTable • 360 columns and 10,000,000 rows • The Skeleton here is trivial • Querying the decomposed XML version can be as fast as querying the SkyServer database • For queries where SkyServer doesn’t make heavy use of indexes, which are not in VX yet More: http://homepages.inf.ed.ac.uk/v1bchoi/paper.pdf

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