More XML XML schema, XPATH, XSLT CS 431 – February 21, 2005 Carl Lagoze – Cornell University acknowledgements to

xHTML HTML “expressed” in XML Corrects defects in HTML –All tags closed –Proper nesting –Case sensitive (all tags lower case) –Strict well-formedness Defined by a DTD –

xHTML (cont.) All new HTML SHOULD be xHTML W3C validator – Tidy –

A little context Traditional Library Central control Uniform expertise Traditional Web Distributed, interlinked Viewable Documents XML Markup Syntax URIs Name Convention HTTP Access Method Schema Type Definition Namespaces Concept Integration Xpath Data Decomposition XSLT Data Transformation DTD Tag Sets RDF Semantic Relationships OWL Concept Building

XML Schema Define… elements attributes Nesting structure (parent/child rela.) Sibling sequence Sibling cardinality Presence or absence of text values Element and attribute data types Element and attribute default values

Structure of a schema well-formed xml document elements are in schema namespace root is element

Instantiation of a schema Note namespaces!!

Simple vs. Complex Values Element with complex value contains other elements (has children) Element with simple value does not have children (e.g. text).

Simple Value Types Restriction on type of content Syntax – Examples –

Facets Restrictions on values within type context Examples

String types and patterns

Simple Example Memo Schema – p/Examples/Lecture9/memo.xsdhttp:// p/Examples/Lecture9/memo.xsd Instance Document – p/Examples/Lecture9/memo.xmlhttp:// p/Examples/Lecture9/memo.xml

Complex Types Type definition defines elements nesting

Controls on complex types sequence – specific order all – any order choice – only one cardinality – minOccurs, maxOccurs

Complex Type Extension Add values to sequence

Mixed Content

Declaring attributes Define type –xs:string –xs:decimal –xs:integer –xs:boolean –xs:date –xs:time Define optional or required

Use of attributes Always a complex type

Type Reuse

Type Reuse Example Address schema – p/Examples/Lecture9/address.xsdhttp:// p/Examples/Lecture9/address.xsd Person schema – p/Examples/Lecture9/person.xsdhttp:// p/Examples/Lecture9/person.xsd Instance document – p/Examples/Lecture9/person.xmlhttp:// p/Examples/Lecture9/person.xml

XPath Language for addressing parts of an XML document –XSLT –Xpointer Tree model similar to DOM W3C Recommendation (1999) –

Xpath Concepts Context Node –current node in XML document that is basis of path evaluation –Default to root Location Steps – selection from context node –Axis – sub-tree(s) selection from context node –Node Test – select specific elements or node type(s) –Predicates – predicate for filtering after axis and node tests

Axis child: all children of context descendent: all children, grandchildren, … parent: ancestor

Node Test Element name: e.g. “Book” Wildcard: * Type(): where type is “node”, “text”, etc.

Predicate Boolean and comparative operators Types –Numbers –Strings –node-sets Functions –Examples boolean starts-with(string, string) number count(node-set)

Combining all into a location set specification Syntax: axis::node-test[predicate] Examples: –child::Book[position() child elements of context –child::Book/attribute::color – “color” attributes of child elements of context

Abbreviations Child axis is default –child::Book  Book Attribute axis –Book[position() = “.” (self), “..” (parent), “//” (descendent-or-self) position() = n  n Example

XML Transformations (XSLT) Origins: separate rendering from data –Roots in CSS W3C Recommendation – Generalized notion of transformation for: –Multiple renderings –Structural transformation between different languages –Dynamic documents XSLT – rule-based (declarative) language for transformations

XSLT Capabilities Generate constant text Filter out content Change tree ordering Duplicate nodes Sort nodes Any computational task (XSLT is “turing complete”)

XSLT Processing Model Input XML doc Parsed tree Xformed tree Output doc (xml, html, etc) parse XSLTserialize

XSLT “engine” XML input XSLT “program ” XSLT Engine (SAXON) Output Document (xml, html, …)

Stylesheet Document or Program XML document rooted in element Body is set of templates –Xpath expression specifies elements in source tree –Body of template specifies contribution of source elements to result tree Not sequential execution

Template Form Elements from xsl namespace are transform instructions Match attribute value is xpath expression Non-xsl namespace elements are literals.

A simple example XML base file – s/xslt/simple.xmlhttp:// s/xslt/simple.xml XSLT file – s/xslt/simple.xslhttp:// s/xslt/simple.xsl

XSLT Recursive Programming Style Document driven, template matching –Conflict resolution rules –Mode setting –Context setting

XSLT Procedural Programming Sequential programming style Basics –for-each – loop through a set of elements –call-template – like a standard procedure call

For-each programming example XML base file – s/xslt/foreach.xmlhttp:// s/xslt/foreach.xml XSLT file – s/xslt/foreach.xslhttp:// s/xslt/foreach.xsl

Call-template programming example XML base file – s/xslt/call.xmlhttp:// s/xslt/call.xml XSLT file – s/xslt/call.xslhttp:// s/xslt/call.xsl

Result Tree Creation Literals – any element not in xsl namespace - content directly to output - expression processing and - Copy current node or selected nodes into result tree - instantiate an element - instantiate an attribute

Various other programming constructs Conditionals Variables (declaration and use) Some type conversion Sorting

Resources XSLT – WROX Press –ISBN W3C XSLT Page – Arbortext XSL Tutorial –