XSLT and XPath(Ch.8)

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XSLT and XPath(Ch.8)

• PIKE Lab.
• ?? 2??
• ???

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Contents

• Overview of the XSLT
• XPath query language
• The role of template rules
• Match patterns
• The top-level elements
• Some working examples
• Summary
• References

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What is XSLT?

• eXtensible Stylesheet Language Transformation
• A high-level language for defining XML
  transformation
• A versatile tool applied in many different ways

input
output
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Transformation Process
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Transformation Process

• An XML parser takes the source XML document and
  turns it into a tree representation
• The XSLT processor transforms this tree into
  another tree
• A serializer takes the result tree and turns it
  into a XML document

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XSLT as a Programming Language

• XML Syntax
• XSLT stylesheet XML document
• Use the angle brackets and tags of XML

In a XML language
In a conventional language
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XSLT as a Programming Language

• Rule-based
• The rules of XSLT Template rules
• ltxsltemplategt elements in the stylesheet
• Each rule has a match pattern template body
• Example of a simple template rule

ltxsltemplate matchpricegt
ltbgtltxslvalue-of selectformat-number(. ,
0.00) /gtlt/bgt lt/xsltemplategt

• The pattern is price, which matches any
  ltpricegtelement.
• To output the value of the ltpricegt element,
  formatted as a number with two decimal digits

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XSLT as a Programming Language

• XPath Queries
• To fetch the data you need from the source
  document
• Cf.) to describe the logic of the transformation
  process
• ? use XSLT itself
• The syntax of XPath is not at all like SQL
• Designed to process hierarchic data(trees)
• Example XPath expressions

/invoice/billing-address/postcode . .
/_at_title /book/chapter3/section2/para1
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XSLT as a Programming Language

• Functional Programming
• XSLT instructions can be executed in any order
• Not depend on how the previous node was handled
• Each piece of the output is defined as a function
  of a particular piece of the input
• Data Type
• Defined by the query language, XPath
• Node-set
• like a mathematical set ( no intrinsic order,
  no duplicates )
• Character strings, numbers(0,1..), Boolean
  values(T/F)
• Variables
• write-once variables, just names for values
• hold the result of any XPath query
• ? node-set, string, number,Boolean

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XSLT as a Programming Language

• Examples of variables of each kind

ltxslvariable namex select//item
/gt ltxslvariable namey selectcount(_at_)
/gt ltxslvariable namez select_at_typeT
/gt ltxslvariable nametreegt lttablegt lttrgt lttd
gt ltimg srcbutton1.gif /gt lt/tdgt lttdgt
ltimg srcbutton2.gif /gt lt/tdgt lt/trgt lt/tablegt
lt/xslvariablegt

• XSLT
• is a
• dynamically
• typed language
• Automatically
• conversion

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The XPath Data Model

• The tree structure in XSLT XPath is similar in
  many ways to the DOM
• Difference
• In the DOM
• Every node has a nodeValue property
• The nodeValue of an element node is null
• In the XSLT
• Every node has a string-value property
• The string-value of an element node is the
  concatenation of all its descendant text nodes

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The XPath Data Model

• Seven types of node in an XSLT tree
• Root represent the root of the tree
  (corresponding to the Document node in the DOM)
• Element each element node corresponds to an
  element in the source document
• Attribute cf.) xmlns attributes
• Text represent the textual content of the
  document
• Processing Instruction written as
  lt?targetdata?gt
• Comment
• Namespace

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The XPath Data Model

• Names Namespaces
• Element or attribute name
• namespace prefix local name ? qualified
  name(Qname)
• Ex) Qname foblock ? fo prefix, block
  local name
• The namespace declaration defines a namespace URI
  
• Ex) ltfoblockgt ? xmlnsfohttp//www.w3.org.XSL/
  
• In the XML rules, the expanded names of the
  elements and attributes are different

lttemplate matchpara xmlnshttp//www.w3.org/19
99/XSL/Transform/gt
lttemplate matchmypara xmlnshttp//www.w3.
org/1999/XSL/Transform Xmlnsmyurnsome-namesp
ace /gt
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XPath Expressions

• Context
• The result of an XPath expression may depend on
  the context in which it is used
• Context node the node on the source tree for
  which the expression is being evaluated ( access
  by . )
• Context position the position of that node in
  the list of nodes being processed ( access by
  position() )
• Context size the number of nodes in that list(
  access by last() )
• Others from the containing XSLT stylesheet

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XPath Expressions

• Primaries
• The basic building blocks of an XPath expression

Construct Examples
String literal London Paris
Number 12 0.0001 5000000
Variable Reference x myvariable-name
Function call Position() Contains(x, ) Msextension(Bill, Gates)
Parenthesized expression 3 (x 1) (//item)1
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XPath Expressions

• Operators be familiar but not all of them
• Comparing Node-set
• Either or both of the operands is a node-set when
  you use the comparison operators ( , !, lt, gt,
  lt, gt)
• Example,
• //_at_secureyes with the name secure and the
  value yes
• //_at_secure!yes with the name secure a value
  other than yes
• //author//artist with the same string-value
• Exceptions with an empty set, !, ./

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Location Paths

• The construct gave the language its name with
  abbreviations
• Syntax Rules for Location Paths
• Step
• Defines a route through the tree representation
  of the source document
• 3 components Axis, Node test, Predicate
• Axis-name ltltgtgt node-test ( ltltgtgt predicate
  ltltgtgt )

/ Selects the root node
/ step Ex) /comment() Selects nodes that can be reached from the root by the step
E / step Selects nodes that can be reached from nodes in E by the step
Step Ex) descendantfigure Selects nodes that can be reached from the context node by the step
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Location Paths

• Axis
• defines the relationship of the required nodes
  to the starting nodes ( ancestor, child,
  following-sibling )
• Node test
• defines the type of nodes and the names of the
  nodes that are to be selected
• Predicates
• expressions that further restrict the set of
  nodes selected by the step , like a filter on the
  node-set
• Cf.) In a filter expression, the nodes are
  considered in forward document order, while in
  a step, the nodes are taken in axis order

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Location Paths

• Abbreviation
• use some shortcut notations for location paths
• . selfnode() ? context node itself
• Ex) ltparagt ? ltxslif testselfparagt
• . . parentnode()
• _at_ attribute ? to indicate the attribute
  axis
• // /descendant-or-selfnode()
• ? Search for all the descendants of a node
• Child axis is the default axis ? child
• Ex) /section/item ? /childsection/childitem

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XPath Functions
Boolean(arg1) Ceiling(arg1) Concat(arg1, arg2, ) Contains(arg1, agr2) Count(arg1) Current() Document(arg1,arg2) Element-available(arg1) False() Floor(arg1) Format-number(arg1, arg2, arg3) Function-available(arg1) Generate-id(arg1) Id(arg1) Key(arg1, arg2) Lang(arg1) Last() Local-name(arg1) name(arg1) Namespace-uri(arg1) Normalize-space(arg1) Not(arg1) Number(arg1) Position() Round(arg1) Start-with(arg1, arg2) String(arg1) String-length(arg1) Substring(arg1, arg2, arg3) Substring-after(arg1, arg2) Substring-before(arg1, arg2) Sum(arg1) System-property(arg1) Translate(arg1, arg2, arg3) True() Unparsed-entity-uri(arg1)
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Sylesheets, Tmpaltes, Patterns

• ltxslstylesheetgt element
• ltxsltemplategt element like the procedures
  functions

ltxslstylesheet xmlnsxslhttp//www.w3.org/1999
/XSL/Tramsform version1.0gt lt/xslstylesheetgt
ltxsltemplate matchauthorgt ltparagtby
ltxslvalue-of select . /gtlt/paragt lt/xsltemplat
egt
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A example of transformation

• Steps
• Download the sample files from http//www.wrox.com
  
• Download Instant Saxon
• from http//users.iclway.co.uk/mhkay/saxon
• Extract the executable saxon.exe
• into a suitable directory, say c\saxon
• Open an MS-DOS console
• Change directory, and then run the processor
• C\saxon\saxon.exe product.xml product.xsl

lt?xml version"1.0"?gt lt?xml-stylesheet
type"text/xsl" href"products.xsl"?gt ltproductsgt lt
product code"Z123-888" category"tools"gt
ltdescriptiongtLarge claw hammerlt/descriptiongt
ltweight units"gms"gt850lt/weightgt
ltpricegt12.99lt/pricegt lt/productgt ltproduct
code"X853-122" category"books"gt
lttitlegtPlumbing for beginnerslt/titlegt
ltISBNgt0-123-456-9876lt/ISBNgt ltpricegt10.95lt/price
gt lt/productgt ltproduct code"S14-8532"
category"tools"gt ltdescriptiongtAdjustable
spannerlt/descriptiongt ltweight
units"gms"gt330lt/weightgt ltpricegt5.25lt/pricegt lt/
productgt lt/productsgt
lt?xml version"1.0"?gt ltxslstylesheet
xmlnsxsl"http//www.w3.org/1999/XSL/Transform"
version"1.0"gt ltxsloutput method"xml"/gt ltxsltem
plate match""gt ltxslcopygt ltxslcopy-of
select"_at_"/gt ltxslapply-templates/gt lt/xslcopygt
lt/xsltemplategt ltxsltemplate
match"productprice lt 10.00"/gt ltxsltemplate
match"price"/gt lt/xslstylesheetgt
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The contents of a template

• Contents of anltxsltemplategt form a template body
• Attribute value templates
• Parameterize the value by XPath expressions
  within curly brackets
• ltltnamedescriptiongtgt ? nameprefixlocalna
  me
• Restricted allowed in only a few specific
  places
• Ex) ltxslcall-template nametnamegt wont
  work
• XSLT instructions a subset of XSLT elements

ltxslapply-importsgt ltxslapply-templatesgt ltxslattributegt ltxslcall-tempaltegt ltxslchoosegt ltxslcommentgt ltxslcopygt ltxslcopy-ofgt ltxslelementgt ltxslfallbackgt ltxslfor-eachgt ltxslifgt ltxslmessagegt ltxslnumbergt ltxslltprocessing-instructiongt ltxsltextgt ltxslvalue-ofgt ltxslvariablegt
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The contents of a template

• Literal Result Elements
• Any element found within a template body that is
  not recognized as an instruction
• Copied to the result tree with its attributes
  namespaces
• Ex) A literal lttdgt result element
• lttd valigntopgtltxslvalue-of select.
  /gtlt/tdgt
• Generated using XPath expressions
• use ltxslattributegt or xsluse-attribute-sets
  attributes
• Sorting by specifying ltxslsortgt elements
• ltxslsortgt element specifies a sort key and has a
  number of attributes to control sorting

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Top-level Elements

• Can be used as children of the ltxslstylesheetgt
  or ltxsltransformgt element
• Appear in any order, except ltxslimportgt elements
  have to come before any others

ltxslattribute-setgt ltxsldecimal-formatgt ltxslimportgt ltxslincludegt ltxslkeygt ltxslnamespace-aliasgt ltxsloutputgt ltxslparamgt ltxslpreserve-spacegt ltxslstrip-spacegt ltxsltemplategt ltxslvariablegt
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Example displaying soccer results

• Source soccer.xml
• The first stylesheet soccer1.xsl
• Run
• C\saxon\saxon.exe soccer.xml soccer1.xsl

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summary

• XSLT as transformation language for XML documents
• XPath queries within an XSLT stylesheet
• How XSLT SQL database can work together
• ? an application gets XML out of the database,
  and then puts that XML through XSLT stylesheet
  for display

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references

• Microsoft(MSXML3)
• http//msdn.microsoft.com/xml
• Oracle(Oracle XML parser)
• http//technet.orcale.com/
• Saxon
• http//users.iclway.co.uk/mhkay/saxon
• Xalan
• http//xml.apache.org./xalan/overview.html
• Http//www.xslinfo.com