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XML – a data sharing standard

XML – a data sharing standard. DSC340 Mike Pangburn. Data-sharing challenge. Companies need to “talk” across different locations/systems and software Most database systems (and other software applications, e.g., Excel) can read text files formatted as XML. Blind Men and Elephants.

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XML – a data sharing standard

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  1. XML – a data sharing standard DSC340 Mike Pangburn

  2. Data-sharing challenge • Companies need to “talk” across different locations/systems and software • Most database systems (and other software applications, e.g., Excel) can read text files formatted as XML.

  3. Blind Men and Elephants

  4. The ol’ standby: tab (or comma) delimited data… Who: authored it? to contact about data? What: are contents of database? When: was it collected? processed? finalized? Where: was the study done? Why: was the data collected? How: were data collected? processed? Verified? … can be pretty useless!

  5. Metadata • Literally, “data about data” • a set of data that describes and gives information about other data ― Oxford English Dictionary

  6. Early Example of Metadata

  7. Is HTML a good way to share data? <h1> Bibliography </h1> <p> <i> Foundations of Databases </i> Abiteboul, Hull, Vianu <br> Addison Wesley, 1995 <p> <i> Data on the Web </i> Abiteoul, Buneman, Suciu <br> Morgan Kaufmann, 1999

  8. XML: Tags provide meaning (metadata) <bibliography> <book> <title> Foundations… </title> <author> Abiteboul </author> <author> Hull </author> <author> Vianu </author> <publisher> Addison Wesley </publisher> <year> 1995 </year> </book> … </bibliography>

  9. XML vs. HTML

  10. Another example: iTunes Library is XML <dict> <key>Track ID</key><integer>617</integer> <key>Name</key><string>Take Five</string> <key>Artist</key><string>Dave Brubeck Quartet</string> <key>Album</key><string>Time Out</string> <key>Genre</key><string>Jazz</string> <key>Kind</key><string>AAC audio file</string> <key>Size</key><integer>5892093</integer> <key>Total Time</key><integer>363578</integer> …. </dict>

  11. Acct./Fin XML example • XBRL (eXtensible Business Reporting Language) is a language for the electronic communication of business and financial data. • For example, company net profit has its own unique tag. • Edgar Online (SEC company information) uses XBRL • The solution will allow users to request XBRL formatted data for all US equities from within Microsoft Excel, custom templates, and the web.

  12. HTML vs. XML • HTML started with very few tags, but… • HTML now has many tags, and more keep being added over time • Messy, yet not customizable • XML has very few standard tags • You add custom tags that are particular to your data needs

  13. XML helps solves the “Is this an elephant?” problem

  14. More strict tagging rules than HTML The following code is legal in HTML: <p>This is a paragraph <p>This is another paragraph In XML all elements must have a closing tag like this: <p>This is a paragraph</p> <p>This is another paragraph</p> Opening and closing tags must have the same case: <message>This is correct</message> <Message>This is incorrect</message>

  15. More strict tagging rules than HTML In HTML, improperly nested tags like the following are frowned upon, but will not cause an error: <b><i>This text is bold and italic</b></i> In XML all elements must be properly nested within each other like this <b><i>This text is bold and italic</i></b>

  16. no city street person address John name person o555 phone Seattle data Thai Mary name 23456 address 345 Maple id Elementnode Attributenode Valuenode Visualizing XML data: a “Tree” • <data> • <person id=“o555” > • <name> Mary </name> • <address> • <street> Maple </street> • <no> 345 </no> • <city> Seattle </city> • </address> • </person> • <person> • <name> John </name> • <address> Thailand </address> • <phone> 23456 </phone> • </person> • </data>

  17. persons XML: Database data vs. XML Data row row row Database table: phone name phone name phone name • <persons> • <row> <name>John</name> • <phone> 3634</phone></row> • <row> <name>Sue</name> • <phone> 6343</phone> • <row> <name>Dick</name> • <phone> 6363</phone></row> • </persons> “John” 3634 “Sue” 6343 “Dick” 6363

  18. XML data can usually fit a DBMS table… <person> <name> John</name> <phone>1234</phone> </person> <person> <name>Joe</name> </person> • Consider the case of: missing attributes • An acceptable fit withtable • Even though blanks are deemed a bit undesirable in database tables  no phone !

  19. …but the fit is not always good <person> <name> Mary</name> <phone>2345</phone> <phone>3456</phone> </person>  two phones ! • Problematic case: Repeated attributes • A poor fit with table, because database-design rule is that you should not have two columns with the same name: If XML data haddistinct “home” and “cell” columns, the issue goes away

  20. Formatting (visualizing) XML data • Formatting (visualizing in a web page) XML data requires a separate file • What is that separate file? It’s called a“style sheet” • There are a couple different standards for style sheets • XML-specific standard: XSL • Flexible standard: CSS • CSS can be used with both .xml and .html files • We will look at CSS after XML

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