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CBS OPAG-ISS Expert Team on the Assessment of Data Representation Systems (ET-ADRS) Washington DC, USA, 23 - 25 April, 2008. Data Representation System XML. Jan W. Noteboom Royal Netherlands Meteorological Institute (KNMI) noteboom@knmi.nl. Presentation. XML Overview XML SWOT Analysis

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data representation system xml

CBS OPAG-ISS

Expert Team on the Assessment of Data Representation Systems (ET-ADRS)

Washington DC, USA, 23 - 25 April, 2008

Data Representation SystemXML

Jan W. Noteboom

Royal Netherlands Meteorological Institute (KNMI)

noteboom@knmi.nl

presentation
Presentation
  • XML Overview
  • XML SWOT Analysis
  • XML Practical Experiences
  • Discussion

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml overview introduction
XML OverviewIntroduction

XML is:

  • eXtensible Markup Language
  • W3C Recommendation since feb 1998
  • subset of Standard Generalized Markup Language (SGML)
  • meta-language, used to create markup languages
  • designed to represent and exchange data as structured documents across information systems particulary via the Internet
  • human readable (text based, unicode support)
  • open standard, licence free

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml overview structure and semantics
XML OverviewStructure and Semantics

Basic components

  • elements, attributes, comments, PCDATA, processing information (e.g. declaration, namespaces)

Well-formed

  • one root element (hierarchical structure)
  • no open tags, proper nesting:<parentTag><childTag1> </childTag1></parentTag>
  • attributes must be quoted
  • element names are case sensitive

Valid

  • document conforms to some semantic rules(e.g. Document Type Definition DTD or XML Schema XSD)

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml overview structure and semantics5
XML Overview Structure and Semantics

Semantic Rules - XML Schema XSD (W3C, 2001)

  • uses XML syntax (well-formed)
  • structural definitions, type definitions, defaults
  • very powerful and flexible
  • facilitates creation of own libraries with exchange data types

Schemas are also useful for:

  • prior agreements between parties for data exchange
  • application development that process data

Alternatives: RELAX NG (OASIS)*, Schematron*

*Supported by DSDL: Document Schema Definition Languages (ISO 19757)

Namespaces (W3C, 2006):

  • Identify your vocabularies (usage: xmlns:prefix=“URI”)
  • qualify element and attribute names to avoid name collisions
  • Allows modularization of schemas
    • Mix and match elements from multiple schemas in document instances
    • Import or include from one XML Schema into another (re-use)

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml example
XML Example

<?xml version="1.0"?>

<swe:CompositePhenomenon

xmlns:swe="http://www.opengis.net/swe/1.0.1"

xmlns:gml="http://www.opengis.net/gml"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:xlink="http://www.w3.org/1999/xlink"

xsi:schemaLocation="http://www.opengis.net/swe/1.0.1

http://schemas.opengis.net/sweCommon/1.0.1/swe.xsd"

gml:id="weather1" dimension="6">

<gml:name codeSpace="urn:ietf:rfc:2141"

>urn:ogc:def:phenomenon:SEEGrid:weather1</gml:name>

<swe:base xlink:href="urn:ogc:def:phenomenon:OGC:Weather"/>

<swe:component

xlink:href="urn:ogc:def:phenomenon:OGC:AirTemperature"/> <swe:component

xlink:href="urn:ogc:def:phenomenon:OGC:WindSpeed"/> <swe:component

xlink:href="urn:ogc:def:phenomenon:OGC:WindDirection"/> <swe:component

xlink:href="http://sweet.jpl.nasa.gov/ontology/property.owl#Visibility"/>

</swe:CompositePhenomenon>

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml overview processing xml
XML OverviewProcessing XML

API

implementor

XML

Infoset

Application

Programming APIs

  • DOM - Document Object Model
  • SAX - Simple API for XML
  • StAX - Streaming API for XML

Data binding

  • JAXB - Java Architecture for XML Binding
  • Hibernate - relational/object/XML mapping tool

XML

parser

XML

validator

XML

doc

XML

schema

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml overview xml extensions
XML OverviewXML extensions
  • XPath, XPointer: for addressing XML subdocuments
  • XLink : to create hyperlinks between resources
  • XSLT : for rearranging & restructuring XML docs
  • XQuery : for querying
  • SOAP : XML-Protocol for message and object serialization and remote procedure calls
  • RDF : to describe resource metadata
  • XForms : for Web forms
  • XMI : XML Metadata Interchange

…..etc….

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml overview dialects
XML OverviewDialects
  • Geography Markup Language (GML, ISO19136)
  • Keyhole Markup Language (KML)
  • Digital Weather Markup Language (DWML)
  • Climate Data Markup Language (CDML)
  • Weather Markup Language (WxML)
  • Emergency Data Exchange Language (EDXL)
  • Water Markup Language (WaterML)
  • Chemical Markup Language (CML),
  • Electronic Business XML Initiative (ebXML),
  • Scalable Vector Graphics (SVG), . . .

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis
XML SWOT Analysis

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis criteria
XML SWOT AnalysisCriteria
  • Ability/suitability to present WMO dataincludes also: pictorial data, textual information (e.g. warnings), metadata
  • Ability/suitability to exchange dataoperational data between NMHSs and information to users outside NMHSs
  • Ability/suitability for store datausage in storage systems
  • Compliance with and status of existing standards.
  • Available support skills and technology (tooling)
  • Other abilitiesability to translate back and forward to other DRSsability/suitability to envelope objects or act as a pseudo-carrier

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis summary
XML SWOT AnalysisSummary

poor

excellent

ET-ADRS, 23-25 April 2008, Washington DC, USA

slide13
XML SWOT AnalysisPresenting WMO data(weather, climate, water, atmospheric constituents, oceanography, aviation e.a)

Strengths:

  • structured text format (hierarchical)
  • self-documenting
  • can represent common data structures: records, lists, trees
  • human-readable
  • very flexible – you can define and mix other languages (GML)
  • supports modularity (namespaces)

Weaknesses:

  • fairly verbose and partially redundant
  • binary data
  • expressing non-hierarchical relationships is difficult

Opportunities & Threats:

  • many languages and schemes available that are useful to describe weather, climate related aspects
  • potentially complex parsing (many namespaces)

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis presenting wmo data
XML SWOT AnalysisPresenting WMO data

Pictorial data:

  • feature data, vector data (GML, KML)
  • presenting raster data

Remark

  • GML (ISO19136) enables OGC services (WFS, WMS WCS)

Text information (e.g. warnings):

  • XML is human readable and multi-lingual (unicode)
  • EDXL (Emergency Data Exchange Language) by OASIS
  • rearranging & restructuring abilities XSL (to text, XHTML, pdf etc)

Remark

  • CAP – Common Alert Protocol (Oasis), open, based on EDXL

Metadata:

  • ISO 191xx support (ISO 19139 Metadata Schema)

Remark

  • Available WMO Core Metadata Profile (extension to ISO 19139)

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis exchanging operational data nmhs and centers
XML SWOT AnalysisExchanging operational data (NMHS and centers)

Strenghts:

  • strict syntax and parser requirements
  • XML schemes, useful for
    • validating
    • defining exchange formats
    • writing applications that process the data
  • web enabling

Weaknesses:

  • verbose, bandwidth consumption
  • processing overhead (complex parsing, validation)

Opportunities & Threats:

  • data compression (gzip)
  • no agreed WMO schemas, except for Core Metadata

Usage: barely, e.g. Cyclone XML

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis transmitting information users outside nmhss and centers
XML SWOT AnalysisTransmitting information (Users outside NMHSs and centers)

Strenghts:

  • human readable (text)
  • language support (unicode)
  • web enabling (Webservices, SOA support, e-Business)
  • interoperability
  • translation to text or HTML or other XML (XSL)
  • open standard, licence free
  • technology support (tools)

Weaknesses:

  • verbose, bandwidth consumption
  • transmitting binary data

Opportunities & Threats:

  • usage for metadata exchange is common practice (catalogue data)
  • too many proprietary schemas to transmit data

Usage: growing practice , e.g. Road Weather Information Network, Canada

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis usage in storage systems
XML SWOT AnalysisUsage instorage systems

Strenghts:

  • Native XML DBMSs available
  • Many XML enabled relational databases
  • technology such as XPath and XQuery, SQL/XML

Weaknesses:

  • Normalizing/mapping XML data into RDBMS tables can be difficult
  • A native XML DBMS requires more space (less efficient)

Opportunities & Threats:

  • No much experience with XML for storage in NMHSs

Usage: writing XML queries iso SQL (growing practice)

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis standards
XML SWOT AnalysisStandards

Strenghts:

  • XML is open standard (W3C)
  • ISO 191xx standards are supported by XML schemas
  • GML (ISO 19136) – XML for geospatial aspects
  • OGC OM model supported by GML schemas
  • Ability to implement UML conceptual models (ISO 19103) in XML schemes (using XMI)

Weaknesses:

  • No agreed WMO schemas available (except for Core Metadata)

Opportunities (& Threats):

  • All harmonization initiatives are based on ISO, W3C and OGC standards (RA VI: EU-INSPIRE)
  • OGC Observation and Measurement model used to develop WXXM (weather exchange model) for avaition (Eurocontrol)
  • HollowWorld applied to develop WMO Core metadata profile.

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis other abilities
XML SWOT AnalysisOther Abilities

Translating XML from and to other DRSs

  • NetCDF <> XML tooling:
    • (to) NetCDF Markup Language (NcML), and NcML-GML
    • (to&from) LeoNetCDF
  • BUFR <> XML tooling: unknown
  • HDF5 <> XML tooling: (to) d5dump

Combining XML with other data formats

(e.g. envelope, pseudo carrier)

  • XML metadata /header for HDF5, NetCDF or BUFR datasets
  • SOAP (XML protocol) for exchanging data

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis available support skills technology tools
XML SWOT AnalysisAvailable support(skills & technology/tools)
  • Numerous XML extensions(XSL, XQuery XForms, XPath, KML, DWML, SOAP etc.)
    • XMI to translate data models (UML) into XML schemes
    • GML for geospatial aspects (GIS systems)
  • XML technology is widespread, easily available and cheap
  • Increasing number of individuals with XML skills

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml swot analysis summary21
XML SWOT AnalysisSummary

poor

excellent

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml practical experiences
XML practical experiences
  • Cyclone XML, TIGGE project
  • RWIN, Canada
  • WXXM, EUROCONTROL

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml practical experiences23
XML practical experiences

Cyclone XML

  • XML format for cyclone analyses and forecasts (CXML)
  • to improve sharing of cyclone information with other users than NHMSs
  • alternative for the BUFR/CREX format
  • development recently started – TIGGE project
  • details: http://www.bom.gov.au/bmrc/projects/THORPEX/CXML/index.html

RWIN (Road Weather Information Network)

  • XML format for road weather observations (CMML)
  • Interchange between Canadian transportation ministries and contractors (network maintenance)
  • 200 observing sites every 20 minutes
  • Operational
  • details: http://www.clarusinitiative.org/

ET-ADRS, 23-25 April 2008, Washington DC, USA

xml practical experiences24
XML practical experiences

WXXM Weather Exchange model

  • for data and objects related to weather for aviation
  • Conceptual Model (WXCM) based on OGC Observations and Measurements model
  • Following ISO 19100 principles and OGC recommendations
  • using GML for compatibility with third-party GML applications
  • Under development
  • Details:http://www.eurocontrol.int/aim/public/standard_page/met.html

Aeronautical Information Exchange Model (AIXM)

ET-ADRS, 23-25 April 2008, Washington DC, USA

discussion
Discussion

ET-ADRS, 23-25 April 2008, Washington DC, USA

discussion26
Discussion
  • Is there a need to develop a “WMO Markup language”?
  • How to benefit from the extensive and cheap XML support?
  • What synergy XML <> HDF5/BUFR/NetCDF is achievable?
  • What governance should WMO offer to support XML?

ET-ADRS, 23-25 April 2008, Washington DC, USA