xml standards & tools for detector description
DESCRIPTION
XML Standards & Tools for Detector Description. Frank Olken Lawrence Berkeley National Laboratory presented to ATLAS Collaboration May 8, 2000. Outline to Talk. XML Standards Family XML, XML Namespaces, XML Schema, XSLT, SVG, … Express to XML mappings (ISO TC 184 STEP) XML Tools - PowerPoint PPT PresentationTRANSCRIPT
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May 8, 2000 ATLAS Collaboration Page 1
XML Standards & Toolsfor Detector Description
Frank Olken
Lawrence Berkeley National Laboratory
presented to ATLAS Collaboration
May 8, 2000
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Outline to Talk
• XML Standards Family– XML, XML Namespaces, XML Schema,
XSLT, SVG, …
• Express to XML mappings – (ISO TC 184 STEP)
• XML Tools – Parsers, editors, DB load/unload, …
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Purposes of XML
• Intended for document structure mark up
• Intended for data exchange
• Mediocre data modeling facilities
• Not intended for data storage representation
• Portability paramount
• Tends to be verbose (due to mnemonic tags)
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Significance of XML
• Modest technical improvements over prior art
• Major advantage: industry consensus– IBM, Oracle, Microsoft, Sun, Informix, ...
• Implication: lots of tools, portability
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XML 1.0
• Simplified version of SGML (like HTML)
• Markup metalanguage
• Application specific tag sets
• Uses DTDs (Document Type Defn) to specify document structure
• No built-in semantics
• Standard approved several years ago
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XML Namespaces
• Provides segmented address space
• Avoids collisions of tag names
• Full namespaces are URI references (URLs)
• Abbreviated namespace references are “<abbrev:tagname>”
• Hot debate of usage as values (references)
• Approved as W3C recommendation (tags)– usage as data values still being debated
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XML Schema Language
• Will replace DTDs (Doc. Type Def’n.)
• Uses XML syntax– hence can be created and processed with XML
tools
• Has basic datatypes:– integer, float, double, datetime, string, URIref
• Currently in last call, candidate rec. in June
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XML Schema Language (cont.)
• Deficiencies:– Lacks collection types (set, bag, sequence)– Lacks vector, array types– Lacks complex number types– Lacks measurement units– Lacks multiple inheritance– Lacks versioning– Limited extensibility mechanisms
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XML Schema Language (cont.)
• New standards should use XML Schema instead of DTDs !!!
• Advantages:– more, better tools– schema-driven validating parsers can check
basic data types– new tools are emerging now, throughout
summer and fall
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XSLT
• Extensible Style Language (Translation)
• Language to describe XML to XML mappings (or to HTML, or to text)
• Uses XML syntax
• Useful for styling XML (e.g., to HTML)
• Useful for message format translation, etc.
• Standard is in last call.
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DSSSL: Document Style Semantics and Specification
Language
• Developed for formatting SGML
• Can be used with XML
• Based on Scheme (a LISP dialect)
• See Jade (James Clark’s DSSSL Engine)
• See Open Jade project
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Scalable Vector Graphics
• Standard for encoding 2D vector graphics
• Browser plug-ins available now to render – e.g., Adobe, ...
• Allows browser to pan/zoom
• Standard is in last call
• Ugly syntax
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XMI = XML Metadata Interchange Format
• Originally, encoding of UML models in XML
• For exchange of UML models and data stored in UML specified
• Developed by Object Management Group
• Now in version 1.1 (uses namespaces)
• V 1.2 (XML Schema based) in development
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STEP to XML Mappings
• Standard for the Exchange of Product Data
• Includes several geometry representations
• EXPRESS = modeling language – (extended entity relationship model)
• STEP Part 28 – maps STEP datasets/schemas into XML
• Currently being drafted by ISO TC 184
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STEP to XML Mappings (cont.)• XML encoding of EXPRESS schemas
• Multiple encodings of STEP data to XML
• Late binding STEP data to XML– generic XML DTD, not schema specific– limited utility
• Early Binding STEP to XML– attribute-based encoding (poor)– element-based encoding (preferred)
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STEP to XML Mappings (cont.)
• EXPRESS to UML mapping– UML = Unified Modeling Language– UML popular modeling methdology
• UML to XML mapping– Called XMI by Object Mgt. Group– Hence: EXPRESS -> UML -> XMI– Advantage: exploits UML to XMI tools– Disadvantage: complex, verbose XML
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XML Tools
• XML Schema editors
• Structured XML document editors
• XSLT Stylesheet editors/debuggers
• XML Parsers
• XSLT engines
• Storage/query engines
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XML DTD / Schema Editors
• Structured editors for XML DTDs, Schemas
• Used to create document structure specs
• XML Authority schema editor– from Extensibility– handles multiple DTD/schema languages
• IBM’s alphaWorks Schema Editor
• XML Spy, et al. …
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XML Structured Document Editors
• DTD / schema based editors
• Used for word processing, data entry, ...
• Context constrained tag generation
• Automatic generation of closing tags
• Immediate datatype checking (if schemas)
• Xmetal, Adept, XML Pro, …
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XML Stylesheet Editors
• Structure-based editor for XSLT stylesheets
• Multi-window user interface – (XML source, XSLT stylesheet, output)
• XSLT Debugging tools– single step execution– identification of which rule fired
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XML Parsers
• Parsers process XML input files for applications programs
• Non-validating parsers only check for well formedness – (matching opening and closing tags)
• Validating parsers check syntax – (conformance to DTD/schema)
• Use validating parsers - catch errors early
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XML Parser API’s
• SAX 1.0 and 2.0– event-based, – suitable for stream processing - e.g. querying
• DOM API– based on Document Object Model (parse tree)– requires entire DOM in memory– suitable for sorting portions of document,
restructuring documents, etc.
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XML Parsers (cont.)
• Many good free parsers available
• Available in C, C++, Java, Python, Perl
• XP (J. Clark), RXP (R. Tobin), ...
• IBM, Sun, Microsoft, Oracle, ...
• IBM + Sun donated to Apache
• Schema support this spring or summer
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XSLT Processors
• XSLT = XSL Transformation Language
• XML to XML or HTML (or text)
• Suitable for most message reformatting
• Also for XML to XSL formatting objects
• XT (James Clark)
• Saxon (Windows xx only)
• Lotus XSL (Java Bean from IBM )
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Browser support of XML
• IE 5.0 (now) has (nonstd.) XML support– directly renders XML
• Netscape 6.0 (April) may render XML(?)
• Opera 4.0 (alpha now) supports XML
• Alternatives:– server side translation to HTML– plug-ins (e.g. transcode to HTML)
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XML Storage
• Alternative approaches:– relational DBMS– hybrid object/relational DBMS– object oriented DBMS
• How finely to decompose document?
• Vendors:– Excelon, IBM, Oracle, Software AG, Informix,
Infoshark
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XML Query Engines
• W3C XML Query Language WG at work
• XML QL will permit direct query of XML– synthesis of XML encoded query results
• Proposals:– IBM, Microsoft, ATT, Software AG, …
• Products:– Nimble.com
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Conclusions
• XML Schema Lang. v.1.0 is nearly done
• Use XML Schema Language not DTDs
• Use schema-driven validating parsers
• Use SVG for 2D Vector Graphics
• Many schema driven document editors available shortly (XML Spy, Xmetal, …)
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Acknowledgements
• This work has been supported entirely by the U.S. Environmental Protection Agency.
• Program managers: Bruce Bargmeyer and Mike Cullen.
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XML Information Sources
• w3c.org (World Wide Consortium - XML stds) • xml.com (O’Reilly web site)• Robin Cover’s XML Web Page at OASIS• oasis-open.org (XML DTD/Schema Registry)• ebxml.org (e-commerce architecture)• biztalk.org (Microsoft)• xml.apache.org (XML in Apache webserver)
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XML Information Sources
• wfmc.org (Workflow Mgt. Coalition - now AIIM)• XML Journal, XML Magazine, ...• gca.org
– XTECH Conference (February in San Jose)
– XML Europe Conference (June in Paris)
– Extreme Markup Conference (August in Montreal)
– XML 2000 (Washington, DC in December)
• Inside DTDs (book on scientific MLs)