XMLXSL and Information

1
XML/XSL and Information

• continue with XML/XSL
• Ideas from Edward Tufte on data density data
  junk
• Homework find report on data presentation,
  Tufte, statistics, graphs

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Comments on XSLT

• declarative as opposed to procedural language
• no side effects (variables can't be changed,
  order of application of templates is somewhat
  flexible)
• one main use is matching parts of XML tree using
  patterns and 'declaring' results
• push processing pushes out results based on
  applying templates
• pull processing pulls in relevant information
  and produces results

3
Comments, cont.

• XML still under development (definition of next
  standard)
• New version will have what are now done with
  so-called extensions.
• Other options are server-side or client side
  programming
• XML Schema possible replacement for DTDs
• XML-Formatting Objects focus more on formatting

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XSLT examples

• use of variables defined by more intricate
  Xpath expressions
• use of recursive calls to named templates
• template calling itself with new parameters
• Other mechanisms (for you to look up as needed)
• mode for template facility to examine (transform
  the same nodes under different conditionsmodes)
• key function facility to categorize nodes
  according to some calculated expression.

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World cup data

• Previous example transformed each match,
  dependent on whether or not match marked as
  'feature' in attribute.
• What about producing a table of the results?

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What do we want to do

• Transform logic
• produce HTML table, one row for each team
• calculate for team certain values that use all
  the matches that that team is 'in'.
• Implementation
• use XSLT variables

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XSLT mechanics

• ltxslvariable name"teams" select"//teamnot(.pr
  ecedingteam)"/gt
• The value of variables is set by the Select
  pattern. THEY CANNOT BE CHANGED.
• The //team means find all the team nodes
  anywhere.
• The . means the node you are considering now.
• The square brackets define a condition for which
  teams are to be selected. This variable is a
  node set.
• the preceding is an example of what is called
  an axis. It is a qualifier.
• This says make up a node set consisting of
  teams, but don't include any that have occurred
  previously.

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• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltxsltransform
• xmlnsxsl"http//www.w3.org/1999/XSL/Transform"
  version"1.0"gt
• ltxsloutput method"html"/gt
• ltxslvariable name"teams" select"//teamnot(.pr
  ecedingteam)"/gt
• ltxslvariable name"matches" select"//match"/gt
• ltxsltemplate match"/results"gt
• lthtmlgt
• ltheadgtlttitlegtResults of World Cup
• lt/titlegt
• ltLINK REL"stylesheet" TYPE"text/css"
  HREF"results.css"/gt
• lt/headgt
• ltbodygt
• lth2gt Results of World Cup lt/h2gt

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• lttable cellpadding"5"gt
• lttrgt
• ltthgt Team lt/thgt
• ltthgt Played lt/thgt
• ltthgt Won lt/thgt
• ltthgt Lost lt/thgt
• ltthgt Tied lt/thgt
• ltthgt For lt/thgt
• ltthgt Against lt/thgt
• ltthgt Points lt/thgt
• lt/trgt

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indicates variable

• ltxslfor-each select "teams"gt
• ltxslvariable name"this" select"."/gt
• ltxslvariable name"played" select"count(match
  esteamthis)"/gt
• ltxslvariable name"won" select"count(matches
  team.this/_at_score gt team.!this/_at_score)
  "/gt
• ltxslvariable name"lost" select"count(matches
  team.this/_at_score lt team.!this/_at_score)
  "/gt
• ltxslvariable name"tied" select"count(matches
  team.this/_at_score team.!this/_at_score)"/gt
  
• ltxslvariable name"for" select"sum(matches/te
  am.current()/_at_score)"/gt
• ltxslvariable name"against" select"sum(matche
  steamcurrent()/team/_at_score)-for"/gt
• ltxslvariable name"points" select"3wontied
  "/gt

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• lttrgt
• lttdgtltxslvalue-of select"."/gtlt/tdgt
• lttdgtltxslvalue-of select"played"/gtlt/tdgt
• lttdgtltxslvalue-of select"won"/gtlt/tdgt
• lttdgtltxslvalue-of select"lost"/gtlt/tdgt
• lttdgtltxslvalue-of select"tied"/gtlt/tdgt
• lttdgtltxslvalue-of select"for"/gtlt/tdgt
• lttdgtltxslvalue-of select"against"/gtlt/tdgt
• lttdgtltxslvalue-of select"points"/gt lt/tdgt
• lt/trgt
• lt/xslfor-eachgt
• lt/tablegt
• lt/bodygt lt/htmlgt
• lt/xsltemplategt
• lt/xsltransformgt

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New example

• http//99-bottles-of-beer.ls-la.net/
• A web site with programs in over 300 different
  programming languages to display all verses to
• This is my version in xml/xslt
• They have another version that is xslt
  stand-alone. Check it out.

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Example

• lt?xml version"1.0" ?gt
• lt?xml-stylesheet href"lyrics.xsl"
  type"text/xsl"?gt
• lt!DOCTYPE lyrics
• lt!ELEMENT lyrics (line1, line2, line3)gt
• lt!ATTLIST lyrics start CDATA REQUIREDgt
• lt!ELEMENT line1 (PCDATA)gt
• lt!ELEMENT line2 (PCDATA)gt
• lt!ELEMENT line3 (PCDATA)gt
• gt
• ltlyrics start"3"gt
• ltline1gt bottles of beer on the walllt/line1gt
• ltline2gt bottles of beerlt/line2gt
• ltline3gt take one down and pass it
  aroundlt/line3gt
• lt/lyricsgt

could be 99
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Document Type Definition

• defines what is a valid XML document
• Validation can be done with external validator
• http//www.stg.brown.edu/service/xmlvalid/xmlvalid
  .var
• Alternative to DTD is XML Schema
• XML Schemas are XML trees.
• less advanced with respect to being official
  standard

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Demonstration

• Go to
• http//www.stg.brown.edu/service/xmlvalid/xmlvalid
  .var
• (Since it is short), copy and paste lyrics.xml
  into text area
• Click on validate
• returns ok
• Now, change xml to NOT match DTD
• remove start attribute
• add element
• Click on validate
• indicates problems

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What do we want to do?

• Transformation
• produce well-formed HTML
• start with the 'start' attribute and, using it as
  a string, output it as start of first line.
• output as HTML the line.
• using start as number, subtract one to get new
  value. Using this value as a string, output with
  line1.
• repeat process
• Implementation
• The 'repeat' will be done as a recursive call,
  that is, a template will call itself.
• The template will be a named template, with
  parameter the value, starting with the value of
  the start attribute.

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Outline of the xsl file

• header/instructional stuff
• template that matches the main node (lyrics)
• the so-called named template to be called by the
  main template AND also called by itself

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Technical note

• ltxslcopygt and ltxslcopy-ofgt copies information
  from the source document to the result.
• ltxslcopygt copies only the node whereas
  ltxslcopy-ofgt copies the node and any descendants
  (called a deep copy)
• In this example, either could be used.

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• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltxsltransform xmlnsxsl"http//www.w3.org/1999/
  XSL/Transform" version"1.0"gt
• ltxsloutput method"html"/gt
• ltxsltemplate match"/lyrics"gt
• lthtmlgtltheadgtlttitlegtSinging lt/titlegtlt/headgt
• ltbodygt
• ltxslcall-template name"singverse"gt
• ltxslwith-param name"counter"gt
• ltxslvalue-of select"_at_start"/gt
• lt/xslwith-paramgt
• lt/xslcall-templategt
• lt/bodygt lt/htmlgt
• lt/xsltemplategt

templates can have parameters. Here one parameter
is set with value of start attribute.
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• ltxsltemplate name"singverse"gt
• ltxslparam name"counter" /gt ltbr/gt
• ltxslcopy-of select"counter"/gt ltxslvalue-of
  select"line1" /gt
• ltbr/gt
• ltxslcopy-of select"counter"/gtltxslvalue-of
  select"line2" /gt
• ltbr/gt
• ltxslvalue-of select"line3" /gt ltbr/gt
• ltxslvariable name"next" select"counter - 1"
  /gt
• ltxslcopy-of select"next"/gt ltxslvalue-of
  select"line1" /gt
• ltbr/gt ltbr/gt
• ltxslif test"next gt1" gt
• ltxslcall-template name"singverse"gt
• ltxslwith-param name"counter" select"next"
  /gt
• lt/xslcall-templategt
• lt/xslifgt lt/xsltemplategt lt/xsltransformgt

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User centered design

• Build the interface/application for the person
  using it! This is generally not you.
• (Sometimes), it is important to distinguish
  between the system owner and system users.
• If possible, use a more descriptive name client,
  customer, patient, player, museum visitor,
  tourist, for users.
• Determine for the user(s), what is best
• organization
• vocabulary
• Determine for the user(s), what are the
  important/all
• platform, access, etc.

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Challenges

• More than one 'user' category
• first time (novice) versus repeat (expert)
• System owners (the paying client) may want system
  to serve different audiences
• intranet, employees at client locations,
  employees at hotels and on planes, perhaps using
  cell phones.
• Web sites visitors may enter site in different
  ways.
• Search engines may make it important for what you
  think of as inner pages to be stand-alone.

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Data presentation

• Edward Tufte (and others) promote presentation of
  data that features the data as opposed to (what
  he calls) chartjunk.
• You need datacontent.
• Compare amount of space devoted to data versus
  everything else, including
• descriptions, annotation, labels
• illustration without content
• Also, make sure space for navigation is not
  overdone.

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Tufte Challenges of display

• 'life' is multi-dimensional, multi-variety but
  paper and screens are two-dimensional.
• How do you escape flatland?
• Your content may require more resolution than you
  have, especially if limited by computer screens
• How do you manage data density?
• Solution thoughtful, inventive, creative design!
• Design is clear thinking made visible.

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Tufte advice

• What's the problem? Who cares? (why care)? What
  is solution?
• Particular general particular
• Teaching by examplestudy books
• Minard march
• Connecticut radar
• Challenger disaster
• (Columbia disaster)

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Connecticut auto deaths

• Traffic deaths following (intervention) of radar
• no context
• Is it normal fluctuation, with 'normal'
  regression to the mean after an extreme (outlier)
  year or the effects of policy?
• Need to look at context (in space and time)

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Challenge Disaster

• Failure of---technical presentation
• The Morton Thiokol engineers did not want to
  approve the launch because they thought that the
  O-rings would not work in cold weather.
• They made a presentation, which did not succeed.
• The launch went. Their prediction was correct!

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Tufte's proposal
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Principles

• Show visual comparisons. Try to make comparisons
  in space and not 'stacked in time'
• Show causality.
• Show multi-variables/dimensions.
• Integrate word, number and image.
• Document where did data come from? Annotate.
• Everything depends on quality, relevance and
  integrity of content.

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Screen

• Term screen real estate used to indicate the
  value of each part of the screen.
• You (system owners) may need to share screen with
  other organizations, for example, ad space.
• White space, that is, space with nothing on it,
  is valuable for clarity.

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Data dimension

• The data that is worth presenting in graphics
  form (as opposed to clear text) is generally
  complex multi-dimensional. more on this next
  class.
• Tufte (and others) don't give data dimensions it
  doesn't have.
• recall 3D bar graph
• recall army marching in and out of Russia.
• New York Times interactives on 9/11 focused on
  time, location in the towers, Fire Companies from
  different places in NYC. Audio was often real
  police calls, calls on cell phones.

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As with 3D bar charts when you only have points,
avoid rainbow, when the data is
one-dimensional(Note shades of blue chart
better for color-blind visitors.)
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My defense

• Tufte recommends no PowerPoint (no charts with
  bullets)
• I try for whole sentences.
• I avoid decorations.
• Charts are my notes (which I share with you).

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Homework

• Find and report via CourseInfo on one of these or
  related topics Tufte, visual presentation,
  good/bad use of graphs, user-centered design.
• Continue taking on-line XML/XSLT tutorials.
• Do your own versions of XML/XSLT exercises
• (Try writing (simple) DTD and doing validation.)