XML DOCUMENTS & DATABASES

Summary of Introduction to XML HTML vs. XML Types of Data Basics of XML XML Syntax, XML Elements, XML Attributes XML Document Type Definition - Types, Elements, Attributes, Example XML Schema - XSD vs. DTD, Simple elements, Complex elements, Attributes, Facets, Indicators

XML & Databases Extracting XML Documents from Relational Databases XML Querying: XPath XQuery

Extracting XML Documents

Extracting XML Documents

Extracting XML Documents

Extracting XML Documents

Extracting XML Documents

Extracting XML Documents

Extracting XML Documents

XML QUERYING XML PATH LANGUAGE - XPath XML QUERY LANGUAGE - XQuery

XML PATH LANGUAGE - XPATH XPath is a language for addressing parts of an XML Document. XPath uses paths to define XML elements XPath defines a library of standard functions XPath is not written using XML Syntax XPath is a W3C Standard !! XPath provides common syntax and semantics for XSLT and XPointer

XPath – XML Data model root nodes element nodes text nodes attribute nodes namespace nodes processing instruction nodes comment nodes

XPath Basics - Path In general -> sandeep/xml/xmlpath.ppt In XPath -> /catalog/cd/price

XPath Syntax with examples (overview) Locating nodes: /catalog/cd/price (absolute path), //cd Unknown elements: Use wildcard (*) /catalog/*, /*/*/price , // * Several paths: //title | // artist Selecting attributes: Use prefix (@) //@country , /catalog/cd[@country = ‘UK’] , //cd[@*] Specifying Predicates: /catalog/cd[1] , //cd[price], //cd[price = 10]/price

XPath – Location Path Most important grammatical construct in the XPath language, that results in a node-set. EBNF format: Location ::= RelativeLocationPath | AbsoluteLocationPath AbsoluteLocationPath: /step/step/... RelativeLocationPath: step/step/...

XPath – Location Path EBNF format: Location ::= RelativeLocationPath | AbsoluteLocationPath AbsoluteLocationPath::=‘/’RelativeLocationPath? | AbbreviatedAbsoluteLocationPath RelativeLocationPath::=Step|RelativeLocationPath ‘/’ Step | AbbreviatedRelativeLocationPath

XPath – Location Path Location Step has three parts: An Axis – Tree Relationship A Node Test – Node type, expanded-name Zero or more Predicates – Expressions to refine set of nodes. Syntax: axisname :: nodetest [predicate] Example: child :: price [price = 10] Context: context node, context position, context size, variable bindings, function library, namespace declarations

XPath – Location Path – Uabbreviated Axis Names

XPath – Location Path - Examples child::cd , child::*, child::text() attribute::name,attribute::* descentant::catalog, descendant-or-self::cd child::catalog/self::cd, child::cd[position() = last()] /descendant::cd, /descendant::catalog/child::cd child::para[position()=5][attribute::type=“warning”]………what if .. [att..][pos..] child::*[self::cd or self::catalog]

XPath – Predicates A Predicate filters a node-set to a new node-set. The condition is placed in [ ]

XPath – Abbreviated Syntax Examples: cd, *, text(), @src, @*, cd[1], cd[last()], */cd, //cd, cd[@type and @country], .., ., cd[5][@type=“classic”], ../@src, .//cd cd[@type=“classic”][5]

XPath - Expressions Types: Numerical -> + ,- ,* ,div , mod Equality -> =, != Relational -> <,>,<=,>= Boolean -> or, and XPath – Functions Node – set functions, Numeric fuctions, String functions, Boolean functions

XPath – Core Function Library Node – Set: count() ; setnumber=count(node-set) id() ; node-set=id(value) last() ; listnumber=last() local-name() ; namestring=local-name(node) name() ; nodestring=name(node) namespace-uri() ; nodeuri=namespace-uri(node) position() ; processednumber=position() Boolean: boolean() ; bool = boolean(value) false() ; number(false()) lang() ; bool = lang(language) not() ; not(false()) true() ; number(true())

XPath – Core Function Library – String concat() ; string=concat(val1, val2, ..) contains() ; bool=contains(val,substr) normalize-space() ; string=normalize-space(string) starts-with() ; bool=starts-with(string,substr) string() ; string(value) string-length() ; number=string-length(string) substring() ; string=substring(string,start,length) substring-after() ; string=substring-after(string,substr) substring-before() ; string= substring-before(string,substr) translate() ; string=translate(value,string1,string2)

XML QUERY LANGUAGE XML Query Language is used to extract data by querying the XML Documents XML is built on XPath which is used in writing queries XML Query and XML Path have same Data Model, Function Library, Data types, Operators XML Query is not yet a W3C Standard !

XML Query Language – Extracting Nodes Using Functions doc(example.xml) Using Functions and Paths doc(example.xml)/catalog/cd or doc(..)//cd Using Expressions doc(example.xml)/catalog/cd[price < 10]

XML Query – FLOWR Expression For <variable bindings to individual nodes> Let <variable bindings to a collection of nodes> Order by <query specifications> Where <conditions> Return <query result specifications>

XML QUERY - Example

ANY “QUERIES”? Hint: use xml

REFERENCES Fundamentals of Database Systems, Fourth Edition, Elmasir and Navathe www.w3schools.com www.w3.org