Sapossnek XML
Mark CS 594 Computer Science Department Metropolitan College Boston University
Learning Objectives
Learn what XML is Learn the various ways in which XML is used Learn the key companion technologies Learn how to use the .NET framework to read, write, and navigate XML documents
Agenda
Overview Syntax and Structure The XML Alphabet Soup XML in .NET Relational Data and XML
What is XML?
A tag-based meta language Designed for structured data representation Represents data hierarchically (in a tree) Provides context to data (makes it meaningful)
Overview
Self-describing data
Separates presentation (HTML) from data (XML) An open W3C standard A subset of SGML
vs. HTML, which is an implementation of SGML
What is XML?
XML is a "use everywhere" data specification
XML XML
Overview
Application X Documents
XML XML
Configuration
Repository
Database
Documents vs. Data
XML is used to represent two main types of things:
Overview
Documents
Lots of text with tags to identify and annotate portions of the document Hierarchical data structures
Data
XML and Structured Data
Pre-XML representation of data:
"PO 1234","CUST001","X9876","5","14.98 XML representation of the same data: " <PURCHASE_ORDER> <PO_NUM> PO1234 </PO_NUM> <CUST_ID> CUST001 </CUST_ID> <ITEM_NUM> X9876 </ITEM_NUM> <QUANTITY> 5 </QUANTITY> <PRICE> 14.98 </PRICE> </PURCHASE_ORDER>
Overview
Benefits of XML
Open W3C standard Representation of data across heterogeneous environments
Overview
Cross platform Allows for high degree of interoperability Syntax Structure Case sensitive
Strict rules
Who Uses XML?
Submissions by
Overview
Microsoft IBM Hewlett-Packard Fujitsu Laboratories Sun Microsystems Netscape (AOL), and others... SOAP, ebXML, BizTalk, WebSphere, many others...
Technologies using XML
Agenda
Overview Syntax and Structure The XML Alphabet Soup XML in .NET Relational Data and XML
Components of an XML Document
Elements
Syntax and Structure
Each element has a beginning and ending tag
<TAG_NAME>...</TAG_NAME>
Elements can be empty (<TAG_NAME />) Describes an element; e.g. data type, data range, etc. Can only appear on beginning tag Encoding specification (Unicode by default) Namespace declaration Schema declaration
Attributes
Processing instructions
Components of an XML Document
<?xml version="1.0" ?> <?xmlstylesheet type="text/xsl" href="template.xsl"?> <ROOT> <ELEMENT1><SUBELEMENT1 /><SUBELEMENT2 /></ELEMENT1> <ELEMENT2> </ELEMENT2> <ELEMENT3 type=`string'> </ELEMENT3> <ELEMENT4 type=`integer' value=`9.3'> </ELEMENT4> </ROOT>
Syntax and Structure
Elements with Attributes Elements Prologue (processing instructions)
Syntax and Structure
Rules For Well-Formed XML
There must be one, and only one, root element Sub-elements must be properly nested
A tag must end within the tag in which it was started Defined by an optional schema
Attributes are optional
Attribute values must be enclosed in "" or `' Processing instructions are optional XML is case-sensitive
<tag> and <TAG> are not the same type of element
Syntax and Structure
Well-Formed XML?
No, CHILD2 and CHILD3 do not nest propertly
<xml? Version="1.0" ?> <PARENT> <CHILD1>This is element 1</CHILD1> <CHILD2><CHILD3>Number 3</CHILD2></CHILD3> </PARENT>
Syntax and Structure
Well-Formed XML?
No, there are two root elements
<xml? Version="1.0" ?> <PARENT> <CHILD1>This is element 1</CHILD1> </PARENT> <PARENT> <CHILD1>This is another element 1</CHILD1> </PARENT>
Syntax and Structure
Well-Formed XML?
Yes
<xml? Version="1.0" ?> <PARENT> <CHILD1>This is element 1</CHILD1> <CHILD2/> <CHILD3></CHILD3> </PARENT>
Syntax and Structure
An XML Document
<?xml version='1.0'?> <bookstore> <book genre=`autobiography' publicationdate=`1981' ISBN=`1861003110'> <title>The Autobiography of Benjamin Franklin</title> <author> <firstname>Benjamin</firstname> <lastname>Franklin</lastname> </author> <price>8.99</price> </book> <book genre=`novel' publicationdate=`1967' ISBN=`0201 633612'> <title>The Confidence Man</title> <author> <firstname>Herman</firstname> <lastname>Melville</lastname> </author> <price>11.99</price> </book> </bookstore>
Syntax and Structure
Namespaces: Overview
Part of XML's extensibility Allow authors to differentiate between tags of the same name (using a prefix)
Frees author to focus on the data and decide how to best describe it Allows multiple XML documents from multiple authors to be merged When a URL is used, it does NOT have to represent a live server
Identified by a URI (Uniform Resource Identifier)
Syntax and Structure
Namespaces: Declaration
Namespace declaration examples:
xmlns: bk = "http://www.example.com/bookinfo/" xmlns: bk = "urn:mybookstuff.org:bookinfo" xmlns: bk = "http://www.example.com/bookinfo/"
Namespace declaration
Prefix
URI (URL)
Syntax and Structure
Namespaces: Examples
<BOOK xmlns:bk="http://www.bookstuff.org/bookinfo"> <bk:TITLE>All About XML</bk:TITLE> <bk:AUTHOR>Joe Developer</bk:AUTHOR> <bk:PRICE currency=`US Dollar'>19.99</bk:PRICE> <bk:BOOK xmlns:bk="http://www.bookstuff.org/bookinfo" xmlns:money="urn:finance:money"> <bk:TITLE>All About XML</bk:TITLE> <bk:AUTHOR>Joe Developer</bk:AUTHOR> <bk:PRICE money:currency=`US Dollar'> 19.99</bk:PRICE>
Namespaces: Default Namespace
An XML namespace declared without a prefix becomes the default namespace for all sub-elements All elements without a prefix will belong to the default namespace:
<BOOK xmlns="http://www.bookstuff.org/bookinfo"> <TITLE>All About XML</TITLE> <AUTHOR>Joe Developer</AUTHOR>
Syntax and Structure
Syntax and Structure
Namespaces: Scope
Unqualified elements belong to the inner-most default namespace.
BOOK, TITLE, and AUTHOR belong to the default book namespace PUBLISHER and NAME belong to the default publisher namespace
<BOOK xmlns="www.bookstuff.org/bookinfo"> <TITLE>All About XML</TITLE> <AUTHOR>Joe Developer</AUTHOR> <PUBLISHER xmlns="urn:publishers:publinfo"> <NAME>Microsoft Press</NAME> </PUBLISHER> </BOOK>
Syntax and Structure
Namespaces: Attributes
Unqualified attributes do NOT belong to any namespace
Even if there is a default namespace
This differs from elements, which belong to the default namespace
Syntax and Structure
Entities
Entities provide a mechanism for textual substitution, e.g. Entity Substitution
&lt; &amp; < &
You can define your own entities Parsed entities can contain text and markup Unparsed entities can contain any data
JPEG photos, GIF files, movies, etc.
Agenda
Overview Syntax and Structure The XML Alphabet Soup XML in .NET Relational Data and XML
The XML `Alphabet Soup'
XML itself is fairly simple Most of the learning curve is knowing about all of the related technologies
The XML `Alphabet Soup'
XML Infoset DTD XSD XDR CSS XSL XSLT XSL-FO Extensible Markup Language Information Set Document Type Definition XML Schema XML Data Reduced Cascading Style Sheets Extensible Stylesheet Language XSL Transformations XSL Formatting Objects Defines XML documents Abstract model of XML data; definition of terms Non-XML schema XML-based schema language An earlier XML schema Allows you to specify styles Language for expressing stylesheets; consists of XSLT and XSL-FO Language for transforming XML documents Language to describe precise layout of text on a page
The XML `Alphabet Soup'
XPath XPointer XLink XQuery DOM SAX Data Island XML Path Language XML Pointer Language XML Linking Language A language for addressing parts of an XML document, designed to be used by both XSLT and XPointer Supports addressing into the internal structures of XML documents
Describes links between XML documents XML Query Language Flexible mechanism for querying XML (draft) data as if it were a database Document Object Model API to read, create and edit XML documents; creates in-memory object model Simple API for XML API to parse XML documents; eventdriven XML data embedded in a HTML page
Data Binding Automatic population of HTML elements from XML data
The XML `Alphabet Soup'
Schemas: Overview
DTD (Document Type Definitions)
Not written in XML No support for data types or namespaces Written in XML Supports data types Current standard recommended by W3C Interim schema proposed by Microsoft Obsoleted by XSD
XSD (XML Schema Definition)
XDR (XML Data Reduced schema)
The XML `Alphabet Soup'
Schemas: Purpose
Define the "rules" (grammar) of the document
Data types Value bounds
A XML document that conforms to a schema is said to be valid
More restrictive than well-formed XML
Define which elements are present and in what order Define the structural relationships of elements
The XML `Alphabet Soup'
Schemas: DTD Example
XML document:
<BOOK> <TITLE>All About XML</TITLE> <AUTHOR>Joe Developer</AUTHOR> </BOOK>
DTD schema:
<!DOCTYPE BOOK [ <!ELEMENT BOOK (TITLE+, AUTHOR) > <!ELEMENT TITLE (#PCDATA) > <!ELEMENT AUTHOR (#PCDATA) > ]>
The XML `Alphabet Soup'
Schemas: XSD Example
XML document:
<CATALOG> <BOOK> <TITLE>All About XML</TITLE> <AUTHOR>Joe Developer</AUTHOR> </BOOK> ... </CATALOG>
The XML `Alphabet Soup'
Schemas: XSD Example
<xsd:schema id="NewDataSet" targetNamespace="http://tempuri.org/schema1.xsd" xmlns="http://tempuri.org/schema1.xsd" xmlns:xsd="http://www.w3.org/1999/XMLSchema" xmlns:msdata="urn:schemasmicrosoftcom:xmlmsdata"> <xsd:element name="book"> <xsd:complexType content="elementOnly"> <xsd:all> <xsd:element name="title" minOccurs="0" type="xsd:string"/> <xsd:element name="author" minOccurs="0" type="xsd:string"/> </xsd:all> </xsd:complexType> </xsd:element> <xsd:element name="Catalog" msdata:IsDataSet="True"> <xsd:complexType> <xsd:choice maxOccurs="unbounded"> <xsd:element ref="book"/> </xsd:choice> </xsd:complexType> </xsd:element> </xsd:schema>
Schemas: Why You Should Use XSD
Newest W3C Standard Broad support for data types Reusable "components"
The XML `Alphabet Soup'
Simple data types Complex data types
Extensible Inheritance support Namespace support Ability to map to relational database tables XSD support in Visual Studio.NET
The XML `Alphabet Soup'
Transformations: XSL
Language for expressing document styles Specifies the presentation of XML
More powerful than CSS XSLT XPath XSL Formatting Objects (XSL-FO)
Consists of:
The XML `Alphabet Soup'
Transformations: Overview
XSLT a language used to transform XML data into a different form (commonly XML or HTML)
XML XML, HTML, ... XSLT
The XML `Alphabet Soup'
Transformations: XSLT
The language used for converting XML documents into other forms Describes how the document is transformed Expressed as an XML document (.xsl) Template rules
Patterns match nodes in source document Templates instantiated to form part of result document
Uses XPath for querying, sorting, etc.
The XML `Alphabet Soup'
Transformations: Example
<sales> <summary> <heading>Scootney Publishing</heading> <subhead>Regional Sales Report</subhead> <description>Sales Report</description> </summary> <data> <region> <name>West Coast</name> <quarter number="1" books_sold="24000" /> <quarter number="2" books_sold="38600" /> <quarter number="3" books_sold="44030" /> <quarter number="4" books_sold="21000" /> </region> ... </data> </sales>
The XML `Alphabet Soup'
Transformations: Example
<xsl:param name="low_sales" select="21000"/> <BODY> <h1><xsl:valueof select="//summary/heading"/></h1> ... <table><tr><th>Region\Quarter</th> <xsl:foreach select="//data/region[1]/quarter"> <th>Q<xsl:valueof select="@number"/></th> </xsl:foreach> ... <xsl:foreach select="//data/region"> <tr><xsl:valueof select="name"/></th> <xsl:foreach select="quarter"> <td><xsl:choose> <xsl:when test="number(@books_sold &lt;= $low_sales)"> color:red;</xsl:when> <xsl:otherwise>color:green;</xsl:otherwise></xsl:choose> <xsl:valueof select="format number(@books_sold,'###,###')"/></td> ... <td><xsl:valueof select="format number(sum(quarter/@books_sold),'###,###')"/>
The XML `Alphabet Soup'
Transformations: Example
The XML `Alphabet Soup'
XSL Formatting Objects (XSL-FO)
A set of formatting semantics Denotes typographic elements (for example: page, paragraph, rule, etc.) Allows finer control obtained via formatting elements
Word, letter spacing Indentation Widow, orphan, hyphenation control Font style, etc.
The XML `Alphabet Soup'
XPath (XML Path Language)
General purpose query language for identifying nodes in an XML document Declarative (vs. procedural) Contextual the results depend on current node Supports standard comparison, Boolean and mathematical operators (=, <, and, or, *, +, etc.)
The XML `Alphabet Soup'
XPath Operators
Operator Usage Description
/ // . * @ [ ] Child operator selects only immediate children (when at the beginning of the pattern, context is root) Recursive descent selects elements at any depth (when at the beginning of the pattern, context is root) Indicates current context Wildcard Prefix to attribute name (when alone, it is an attribute wildcard) Applies filter pattern
The XML `Alphabet Soup'
XPath Query Examples
./author (finds all author elements within current context) /bookstore (find the bookstore element at the root) /* (find the root element) //author (find all author elements anywhere in document) /bookstore[@specialty = "textbooks"] (find all bookstores where the specialty attribute = "textbooks") /book[@style = /bookstore/@specialty] (find books all where the style attribute = the specialty attribute of the bookstore element at the root)
The XML `Alphabet Soup'
XPointer
Builds upon XPath to:
Identify sub-node data Identify a range of data Identify data in local document or remote documents
New standard
The XML `Alphabet Soup'
XLink
XML Linking Language Elements of XML documents Describes links between resources
Simple links (for example, HTML HREFs) Extended links
Remote resources Local resources Rules for how a link is followed, etc.
The XML `Alphabet Soup'
The XML DOM
XML Document Object Model (DOM) Provides a programming interface for manipulating XML documents in memory Includes a set of objects and interfaces that represent the content and structure of an XML document Enables a program to traverse an XML tree Allows elements, attributes, etc., to be added/deleted in an XML tree Allows new XML documents to be created programmatically
The XML `Alphabet Soup'
SAX (Simple API for XML)
API to allow developers to read/write XML data Event based
Uses a "push" model
Sequential access only (data not cached) Requires less memory to process XML data than the DOM
SAX has less overhead (uses small input, work and output buffers) than the DOM DOM constructs the data structure in memory (work and output buffers = to size of data)
The XML `Alphabet Soup'
Data Islands
XML embedded in an HTML document Manipulated via client side script or data binding
<XML id="XMLID"> <BOOK> <TITLE>All About XML</TITLE> <AUTHOR>Joe Developer</AUTHOR> </BOOK> </XML> <XML id="XMLID" src="mydocument.xml">
The XML `Alphabet Soup'
Data Islands
Can be embedded in an HTML SCRIPT element XML is accessible via the DOM:
SCRIPT language="xml" id="XMLID"> SCRIPT type="text/xml" id="XMLID"> SCRIPT language="xml" id="XMLID" src="mydocument.xml"
The XML `Alphabet Soup'
Data Islands
Access the XML via the HTML DOM:
function returnXMLData() { return document.all("XMLID").XMLDocument.nodeValue; }
Or access the XML directly via the ID:
function returnXMLData() { return XMLID.documentElement.text; }
The XML `Alphabet Soup'
Data Binding
Client-side data binding (in the browser) The XML Data Source Object (DSO) binds HTML elements to an XML data set (or data island) When the XML data set changes, the bound elements are updated dynamically DATASRC: the source of the data (e.g., the ID of the data island) DATAFLD: the field (XML element) to display Can offload XSLT processing to the client IE only
The XML `Alphabet Soup'
Data Binding
<HTML><BODY> <XML ID="xmlParts"> <?xml version="1.0" ?> <parts> <part> <partnumber>A1000</partnumber> <description>Flat washer</description> <quantity>1000</quantity> </part> ... </XML> <table datasrc=#xmlParts border=1><tr> <td><div datafld="partnumber"></div></td> <td><div datafld="quantity"></div></td> </tr></table> </BODY></HTML>
The XML `Alphabet Soup'
XLang (BizTalk)
An XML language for defining processes Processes usually on multiple platforms Support for:
Concurrency Long-running transactions Connect to COM components Connect to MSMQ queues Connect to SQL components
Exposed messaging and orchestration APIs
The XML `Alphabet Soup'
XML-Based Applications
Microsoft BizTalk Server
Enables uniform exchange of data among disparate systems (XLang) Backend interchange with partners/customers XML-based Product Catalog System Integrated with BizTalk Server for backend communication
Microsoft Commerce Server
The XML `Alphabet Soup'
XML-Based Applications
Microsoft SQL Server
Retrieve relational data as XML Query XML data Join XML data with existing database tables Update the database via XML Updategrams XML is native representation of many types of data Used to enhance performance of UI scenarios (for example, Outlook Web Access (OWA))
Microsoft Exchange Server
Agenda
Overview Syntax and Structure The XML Alphabet Soup XML in .NET Relational Data and XML
XML in .NET
Overview
XML use is ubiquitous throughout .NET Web Services
Based on XML standards: SOAP, WSDL, UDDI, ... Application information stored in XML-based configuration files Provides conversion between DataSets and XML DataSets are serialized as XML
ASP.NET
ADO.NET
XML in .NET
Overview
XML classes built on industry standards
e.g., DOM Level 2 Core, XML Schemas, SOAP vs. the traditional SAX "push" model MSXML 3.0 still available in .NET via COM Interop
Introduces a stream-based ("pull") interface
Natural evolution of MSXML 3.0 (4.0)
.NET XML classes are well-factored for functionality, performance and extensibility
Core Classes in System.XML
Abstract (Base) Class XmlNode Concrete (Derived) Class XmlDocument XmlLinkedNode XmlElement XmlAttribute XmlDataDocument XmlTextReader XmlNodeReader XmlTextWriter
XML in .NET
XmlReader XmlWriter
XML in .NET
XmlNode
Represents a single node in a XML document hierarchy An abstract class Properties and methods to
traverse XML document hierarchy query properties modify nodes delete notes
XML in .NET
XmlDocument
Implements W3C XML Document Object Model (DOM) Level 1 and Level 2 specifications Implements XmlNode Represents an entire XML document
All nodes are available to view/manipulate
Cached in memory XmlDocument is analogous to a DataSet Events for changing, inserting and removing nodes
XML in .NET
XmlDocument
Declaration:
public class XmlDocument : XmlNode
Constructor:
public XmlDocument();
Code example:
XmlDocument myXmlDoc = new XmlDocument(); myXmlDoc.Load("c:\Sample.xml");
XmlLinkedNode
Implements XmlNode Retrieves the node immediately preceding or following the current node An abstract class from which XmlElement is derived
XML in .NET
Declaration:
public abstract class XmlLinkedNode : XmlNode
XML in .NET
XmlElement
Represents an element in the DOM tree Properties and methods to view, modify, and create element objects
Declaration:
public class XmlElement : XmlLinkedNode
Code example:
XmlDocument myXmlDoc = new XmlDocument(); myXmlDoc.Load ("c:\Sample.xml"); // DocumentElement retrieves the root element XmlElement root = myXmlDoc.DocumentElement;
XML in .NET
XmlAttribute
Implements XmlNode Represents an attribute of an XmlElement Valid and/or default values defined by schema
Declaration:
public class XmlAttribute : XmlNode
XML in .NET
Code example:
XmlAttribute
mlDocument myXmlDoc = new XmlDocument(); yXmlDoc.Load ("c:\Sample.xml");
/ Get the attribute collection of the root element
lAttributeCollection attrColl = myXmlDoc.DocumentElement.Attributes
/ Create a new attribute and set it's value mlAttribute newAttr = myXmlDoc.CreateAttribute("value"); ewAttr.Value = "new value";
/ Append the new attribute to the collection ttrColl.Append(newAttr);
Demo XmlDocument
XML in .NET
XmlNode:IXPathNavigable
XmlNode has simple methods for traversing a XML document hierarchy XmlNode is an interface for accessing XML data using a cursor model Provides a generic navigation mechanism Support for XPath expressions through IXPathNavigable interface Can select and navigate a subset of a document Properties and methods to view, modify, copy, delete nodes
XML in .NET
XPathNavigator
Allows navigation over a XmlDocument XmlDocument is derived from XmlNode, which implements IXPathNavigable
public class XmlDocument : XMLNode { XMLNode IXPathNavigable.CreateNavigator() { } }
XML in .NET
Caveats
"Current" node remains current when moved Can be in a null state when not pointing to a node Does not "walk" off end of tree Failed methods leave XPathNavigator where it was
XPathNavigator
Declaration:
public class XPathNavigator : IXPathNavigable
XML in .NET
Constructor:
public XPathNavigator (XmlDocument document);
Code example:
XmlDocument myXmlDoc; myXmlDoc.Load ("c:\Sample.xml"); XPathNavigator nav = myXmlDoc.CreateNavigator(); nav.MoveToRoot(); // move to root element nav.MoveToNext(); // move to next element
XPathNavigator
Example: iterate over a subset of nodes
XmlDocument doc = new XmlDocument(); doc.Load("person.xml"); XPathNavigator nav = doc.CreateNavigator(); XPathNodeIterator iter = nav.Select("/person/name"); while (iter.MoveToNext ()) { // process selection here... with iter.Current.Value }
XML in .NET
Example: sum all Prices in a document
public static void SumPriceNodes(XPathNavigator nav) { // in this case, evaluate returns a number Console.WriteLine("sum=" + nav.Evaluate("sum(//Price)")); }
Demo XPathNavigator
XML in .NET
XML in .NET
XmlReader
XmlReader is an abstract class that provides fast, non-cached, forward-only, read-only access to XML data Uses a "pull" model
Simpler than the SAX "push" model User can easily implement "pus...