XML Language Family Detailed Examples

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XML Language FamilyDetailed Examples

• Most information contained in these slide comes
  from http//www.w3.org, http//www.zvon.org/
• These slides are intended to be used as a
  tutorial on XML and related technologies
• Slide authorJürgen Mangler (juergen.mangler_at_univ
  ie.ac.at)
• This section contains examples on
• XPath,
• XPointer

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XPath is the result of an effort to provide a
common syntax and semantics for functionality
shared between XSL Transformations XSLT and
XPointer. The primary purpose of XPath is to
address parts of an XML document.

• XPath uses a compact, non-XML syntax to
  facilitate use of XPath within URIs and XML
  attribute values.
• XPath operates on the abstract, logical structure
  of an XML document, rather than its surface
  syntax.
• XPath gets its name from its use of a path
  notation as in URLs for navigating through the
  hierarchical structure of an XML document.

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• In addition to its use for addressing, XPath is
  also designed to feature a natural subset that
  can be used for matching (testing whether or not
  a node matches a pattern) this use of XPath is
  described in XSLT (next chapter).
• XPath models an XML document as a tree of nodes.
  There are different types of nodes, including
  element nodes, attribute nodes and text nodes.

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• The basic XPath syntax is similar to filesystem
  addressing. If the path starts with the slash / ,
  then it represents an absolute path to the
  required element.

/AAA/CCC Select all elements CCC which are
children of the root element AAA       ltAAAgt
          ltBBB/gt           ltCCC/gt
          ltBBB/gt           ltBBB/gt
          ltDDDgt                ltBBB/gt
          lt/DDDgt           ltCCC/gt      lt/AAAgt
/AAA Select the root element AAA       ltAAAgt
          ltBBB/gt           ltCCC/gt
          ltBBB/gt           ltBBB/gt
          ltDDDgt                ltBBB/gt
          lt/DDDgt           ltCCC/gt      lt/AAAgt
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• If the path starts with // then all elements in
  the document, that fulfill the criteria following
  //, are selected.

//DDD/BBB Select all elements BBB which are
children of DDD       ltAAAgt           ltBBB/gt
          ltDDDgt                ltBBB/gt
          lt/DDDgt           ltCCCgt
               ltDDDgt                     ltBBB/gt
                    ltBBB/gt                lt/DDDgt
          lt/CCCgt      lt/AAAgt
//BBB Select all elements BBB        ltAAAgt
          ltBBB/gt           ltDDDgt
               ltBBB/gt           lt/DDDgt
          ltCCCgt                ltDDDgt
                    ltBBB/gt                     lt
BBB/gt                lt/DDDgt           lt/CCCgt
     lt/AAAgt
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• The star selects all elements located by the
  preceeding path

////BBB Select all elements BBB which have 3
ancestors      ltAAAgt            ltCCCgt
               ltDDDgt                     ltBBB/gt
               lt/DDDgt           lt/CCCgt
          ltCCCgt                ltDDDgt
                    ltBBB/gt                lt/DDDgt
          lt/CCCgt      lt/AAAgt
/AAA/CCC/DDD/ Select all elements enclosed by
elements /AAA/CCC/DDD       ltAAAgt
          ltBBB/gt           ltDDDgt
               ltBBB/gt           lt/DDDgt
          ltCCCgt                ltDDDgt
                    ltBBB/gt                     lt
BBB/gt                lt/DDDgt           lt/CCCgt
     lt/AAAgt
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• The expression in square brackets can further
  specify an element. A number in the brackets
  gives the position of the element in the selected
  set. The function last() selects the last element
  in the selection.

/papers/paperlast() Select the last BBB child
of element AAA       ltpapersgt           ltpaper
author"motschnig"/gt           ltpaper
author"derntl"/gt           ltpaper
author"motschnig"/gt           ltpaper
author"mangler"gt      lt/papersgt
/papers/paper1 Select the first BBB child of
element AAA       ltpapersgt           ltpaper
author"motschnig"gt           ltpaper
author"derntl"/gt           ltpaper
author"motschnig"/gt           ltpaper
author"mangler"/gt      lt/papersgt
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• Attributes are specified by _at_ prefix.

//student_at_matnr Select BBB elements which have
attribute id      ltstudentsgt           ltstudent
matnr"9506264"/gt           ltstudent
matnr"0002843"/gt           ltstudent
name"Hauer"/gt           ltstudent/gt
     lt/studentsgt
//_at_matnr Select all attributes _at_matnr      ltstud
entsgt           ltstudent matnr"9506264"/gt
          ltstudent matnr"0002843"/gt
          ltstudent name"Hauer"/gt
          ltstudent/gt      lt/studentsgt
//studentnot(_at_) Select BBB elements without an
attribute      ltstudentsgt           ltstudent
id"9506264"/gt           ltstudent id"0002843"/gt
          ltstudent name"Koegler"/gt
          ltstudent/gt      lt/studentsgt
//student_at_ Select BBB elements which have any
attribute      ltstudentsgt           ltstudent
id"9506264"/gt           ltstudent id"0002843"/gt
          ltstudent name"Hauer"/gt
          ltstudent/gt      lt/studentsgt
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• Values of attributes can be used as selection
  criteria. Function normalize-space removes
  leading and trailing spaces and replaces
  sequences of whitespace characters by a single
  space.

//studentnormalize-space(_at_name)'hauer' Select
BBB elements which have an attribute name with
value bbb, leading and trailing spaces are
removed before comparison        ltstudentsgt
          ltstudent matnr"9506264"/gt
          ltstudent name" hauer "/gt
          ltstudent name"hauer"/gt
     lt/studentsgt
//student_at_id'b1' Select BBB elements which
have attribute id with value b1       ltstudentsgt
          ltBBB matnr"9506264"/gt
          ltBBB name" hauer "/gt           ltBBB
name"hauer"/gt      lt/studentsgt
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• Function count() counts the number of selected
  elements

//count()3 Select elements which have 3
children    ltAAAgt           ltCCCgt
               ltBBB/gt                ltBBB/gt
               ltBBB/gt           lt/CCCgt
          ltDDDgt                ltBBB/gt
          lt/DDDgt           ltEEEgt
               ltCCC/gt           lt/EEEgt
     lt/AAAgt
//count(BBB)2 Select elements which have two
children BBB      ltAAAgt           ltCCCgt
               ltBBB/gt           lt/CCCgt
          ltDDDgt                ltBBB/gt
               ltBBB/gt           lt/DDDgt
          ltEEEgt                ltCCC/gt
               ltDDD/gt           lt/EEEgt
     lt/AAAgt
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• Several paths can be combined with separator
  ("" stands for "or", like the logical or
  operator in C).

/AAA/EEE //DDD/CCC /AAA //BBB Number of
combinations is not restricted    ltAAAgt
          ltBBB/gt           ltCCC/gt
          ltDDDgt                ltCCC/gt
          lt/DDDgt           ltEEE/gt      lt/AAAgt
AAA/EEE //BBB Select all elements BBB and
elements EEE which are children of root element
AAA      ltAAAgt           ltBBB/gt
          ltCCC/gt           ltDDDgt
               ltCCC/gt           lt/DDDgt
          ltEEE/gt      lt/AAAgt
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Axes are a sophisticated concept in XML to find
out which nodes relate to each other and how.
ltparentgt ltpreceding-sibling/gt
ltpreceding-sibling/gt ltnodegt
ltdescendant/gt ltdescendant/gt lt/nodegt
ltfollowing-sibling/gt ltfollowing-sibling/gt ltpa
rentgt
preceding- sibling
following- sibling
descendant
descendant
The above example illustrates how axes work.
Starting with node an axe would select the equal
named nodes. This example is also the base for
the next two pages.
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• The following main axes are available
• the child axis contains the children of the
  context node
• the descendant axis contains the descendants of
  the context node a descendant is a child or a
  child of a child and so on thus the descendant
  axis never contains attribute or namespace nodes
• the parent axis contains the parent of the
  context node, if there is one
• the following-sibling axis contains all the
  following siblings of the context node if the
  context node is an attribute node or namespace
  node, the following-sibling axis is empty
• the preceding-sibling axis contains all the
  preceding siblings of the context node if the
  context node is an attribute node or namespace
  node, the preceding-sibling axis is empty
• (http//www.w3.org/TR/xpathaxes)

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• The child axis contains the children of the
  context node. The child axis is the default axis
  and it can be omitted.
• The descendant axis contains the descendants of
  the context node a descendant is a child or a
  child of a child and so on thus the descendant
  axis never contains attribute or namespace nodes.

//CCC/descendantDDD Select elements DDD which
have CCC among its ancestors      ltCCCgt
          ltDDDgt                ltEEEgt
                    lt/DDDgt                lt/EEEgt
          lt/DDDgt      lt/CCCgt
/AAA Equivalent of /childAAA      ltAAAgt
          ltBBB/gt           ltCCC/gt      lt/AAAgt
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• XPointer is intended to be the basis of fragment
  identifiers only for the text/xml and
  application/xml media types (they can point only
  to documents of these types).
• Pointing to fragments of remote documents is
  analogous to the use of anchors in HTML. Roughly
  documentxpointer()

ltlink xmlnsxlink"http//www.w3.org/2000/xlink"gt
    xlinktype"simple"gt xlinkhref"mydocu
ment.xmlxpointer(//AAA/BBB1)"gt lt/linkgt
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• If there are forbidden characters in your
  expression, you must deal with them somehow.
• When XPointer appears in an XML document, special
  characters must be escaped according to
  directions in XML.

• The characters lt or must be escaped using lt
  and amp.
• Any unbalanced parenthesis must be escaped using
  circumflex ()

ltlink xmlnsxlink"http//www.w3.org/1999/xlink"
xlinktype"simple" xlinkhref"test.xmlxpointe
r(//AAA position() lt 2)"gt Bzw. xlinkhref"tes
t.xmlxpointer(string-range('(text
in'))"gt lt/linkgt
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• If your elements have an ID-type attribute, you
  can address them directly using the value of the
  ID-type attribute. (Don't forget you must have
  an attribute defined as an ID type in your DTD!)
• Using ID-type attributes, you can easily include
  or jump to parts of documents.
• The example below selects node with id("b1").

xpointer(id("b1")) ltbookgt   ltbook id"b1"
name"XML"gtBad book.lt/bookgt   ltbook id"b2"
name"JAVA"gt Good book.
ltadditionalgtMakes me sleep like a
baby.lt/additionalgt   lt/bookgt   ltbook id"123"
name"42"gtAll answers on only one
page.lt/bookgtlt/bookgt
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• The specification defines one full form and one
  shorthand form (which is an abbreviation of the
  full one).

• Short Form /1/2/3
• Full Form xpointer(/1/2/3)

ltAAAgt   ltBBB myid"b1" bbb"111"gtText in the
first element BBB.lt/BBBgt   ltBBB myid"b2"
bbb"222"gt Text in another element BBB.
      ltDDD ddd"999"gtText in more nested
element.lt/DDDgt      ltDDD ddd"888"gtText in more
nested element.lt/DDDgt      ltDDD ddd"777"gtText
in more nested element.lt/DDDgt   lt/BBBgt   ltCCC
ccc"123" xxx"321"gtAgain some text in some
element.lt/CCCgt lt/AAAgt
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• A location of type point is defined by a node,
  called the container node (node that contains the
  point), and a non-negative integer, called the
  index.
• (//AAA, //AAA/BBB are the container nodes, 1,
  2 is used if more than one container node of
  the same name exists)

xpointer(start-point(//AAA)) xpointer(start-point(
range(//AAA/BBB1))) ltAAAgt?   ltBBB
bbb"111"gtlt/BBBgt   ltBBB bbb"222"gt ltDDD
ddd"999"gtlt/DDDgt   lt/BBBgt    ltCCC ccc"123"
xxx"321"/gt lt/AAAgt
ltAAAgt   ltBBB bbb"111"gtlt/BBBgt   ltBBB
bbb"222"gt ltDDD ddd"999"gtlt/DDDgt   lt/BBBgt?
   ltCCC ccc"123" xxx"321"/gt lt/AAAgt
xpointer(end-point(range(//AAA/BBB2)))
xpointer(start-point(range(//AAA/CCC)))
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• When the container node of a point is of a node
  type that cannot have child nodes (such as text
  nodes, comments, and processing instructions),
  then the index is an index into the characters of
  the string-value of the node such a point is
  called a character-point.
• You can use this to write a link that behaves
  like a search function. It always jumps to the
  first appearance of a string, e.g. the word
  "another".

xpointer(start-point(string-range(//,'another',
2, 0))) ltAAAgt   ltBBB bbb"111"gtText in the
first element BBB.lt/BBBgt   ltBBB bbb"222"gt
Text in a?nother element BBB. ltDDD
ddd"999"gtText in more nested element.lt/DDDgt   lt/
BBBgt   ltCCC ccc"123" xxx"321"gtAgain some text
in some element.lt/CCCgtlt/AAAgt
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• The range function returns ranges covering the
  locations in the argument location-set. For each
  location x in the argument location-set, a range
  location representing the covering range of x is
  added to the result location set.

The range-inside function returns ranges covering
the contents of the locations in the argument
location-set.
xpointer(range(//AAA/BBB2)) ltAAAgt   ltBBB
bbb"111"/gt ltBBB bbb"222"gt   Text in
another element BBB.   lt/BBBgt    ltCCC ccc"123"
xxx"321"/gtlt/AAAgt
xpointer(range-inside(//AAA/BBB2)) ltAAAgt   ltBB
B bbb"111"/gt ltBBB bbb"222"gt   Text in
another element BBB.   lt/BBBgt    ltCCC ccc"123"
xxx"321"/gtlt/AAAgt
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• For each location x in the argument location-set,
  end-point adds a location of type point to the
  result location-set. That point represents the
  end point of location x.

xpointer(end-point(string-range(//AAA/BBB,'another
')))  ltAAAgt   ltBBB bbb"111"gtText in the first
element BBB.lt/BBBgt   ltBBB bbb"222"gt Text
in another? element BBB. ltDDD
ddd"999"gtText in more nested element.lt/DDDgt   lt/
BBBgt   ltCCC ccc"123" xxx"321"gtAgain some text
in some element.lt/CCCgt lt/AAAgt