Introduction to XML

1
Introduction to XML

• ISYS 464

2
HTML vs XML

• HTML is a language specifically designed for
  displaying information in browser. It doesnt
  carry information about the structure of the
  content held within its page.
• XML (Extensible MarkUp Language) is a language
  used to represent data in a form that does not
  rely on any particular proprietary technology.
  It uses user-defined tags to give meaningful
  names to data elements. With XML, we separate the
  data content from the data presentation.

3
HTML
ltbodygt lth1gtMy Favorite Booklt/h1gt lth1gtISBN -
1-34567-04-01lt/h1gt ltH1gtAuthorslt/H1gt lth3gtJohn
Smithlt/h1gt lth3gtPeter Chenlt/h1gt lth1gtPrice
45.00lt/h1gt lth1gtDescription This is a grerat
booklt/h1gt lt/bodygt
4
XML
lt?xml version"1.0" ?gt ltBooksgt ltBookgt ltISBNgt1-3456
7-04-01lt/ISBNgt ltAuthorsgt ltAuthorNamegtJohn
Smithlt/AuthorNamegt ltAuthorNamegtPeter
Chenlt/AuthorNamegt ltAuthorNamegtDavid
Chaolt/AuthorNamegt lt/Authorsgt ltPricegt
45.00lt/Pricegt ltDescriptiongtThis is a grerat
booklt/Descriptiongt lt/Bookgt ltBookgt ltISBNgt1-34567-04
-02lt/ISBNgt ltAuthorsgt ltAuthorNamegtAdam
Smithlt/AuthorNamegt lt/Authorsgt ltPricegt
25.00lt/Pricegt ltDescriptiongtThis is a second
great booklt/Descriptiongt lt/Bookgt lt/Booksgt
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XML Document

• Well-formed documents
• Documents comply with the rules of XML syntax.
• Valid documents
• Documents that are well-formed and comply with a
  XML schema or Document Type Definition (DTD is a
  file containing the rules used to define the
  document).

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Well-Formed Documents

• There is only one root node.
• All elements must have a start tag and an end tag
  (except for an empty element, see example below)
  Elements must be nested correctly.
• If an element has an attribute, the attribute
  value must be quoted.
• An empty element with an attribute
• ltprice US49 /gt
• Note XML is case sensitive.

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XML Documents

• The XML declaration
• lt?xml version1.0 ?gt
• Note xml should be in lower case.
• Namespaces
• Define a namespace xmlnsuri where the Uniform
  Resource Identifier is a unique identifier and is
  often a URL.
• Use a namespace to make a tag unique
• ltnamespace TagNamegt
• Elements
• Each start-tag/end-tag pair, with the data that
  lies between them, is an element.
• Ex. ltAuthorNamegtJohn Smithlt/AuthorNamegt
• The start and end tag must be in the same case.

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• Attributes Elements can have attributes. These
  are values that are passed to the application,
  but not constitute part of the content of the
  element. Attributes are included as part of the
  elements start tag, and values must be enclosed
  in quote marks.
• ltFood healthyyesgtSpinachlt/Foodgt
• ltFood healthyyes tastynogtCarrotlt/Foodgt

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• Comments
• lt!--This is a comment --gt
• Processing instructions These allow documents to
  contain instructions for applications using XML
  data.
• lt?NameOfTargetApplication Instructions for
  application?gt

10
Tree View of XML
Books
Book
Book
ISBN
Authors
Price
Description
ISBN
Authors
Price
Description
Author
Author
Author
11
Valid Documents

• Well-formed documents that conform to an XML
  schema or DTD.
• XML parsers are programs that are able to
  validate an XML document against schema or DTD.
• XML parsers are included in IE5 and Netscapt 6
  and onwards.

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XML SchemaDefinition of an XML Document

• Namespaces Allow element names to be qualified
  to avoid name collisions.
• Complex and simple types
• Elements that contains other elements are complex
  type.
• Cardinality
• minOccurs 0 for optional element.
• maxOccurs specified number or unbounded
• Compositor
• Sequence defines an ordered sequence of
  subelements.
• Choice defines a choice between several possible
  elements.
• Constraints
• Uniqueness contraint

13
VS.Net Tools for XML Document and Schema

• Dataset schema
• XML Schema
• XML Document

14
Style Sheets

• XSL Extensible Stylesheet Language
• Tell the browser how to display the XML document.
• With a style sheet, all of the style rules are
  kept in one file and the source document simply
  links to this file.
• File extension .CSS

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Benefits of Using Style Sheets

• Improve document clarity No tags such as ltfontgt
  in an XML document.
• Allow you to modify the presentation of several
  pages by altering just one file.
• Allow you to present the same data in different
  ways for different purposes.
• Reduce download time by caching the style sheet
  on the client.

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• Browser screen structure
• Page
• Area
• Block Flow Object Taking up the whole line.
• In-Line Flow Object Several in-line objects may
  be on the same line.

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lt?xml version"1.0" ?gt lt?xmlstylesheet
href"books.css" type"text/css"
?gt ltBooksgt ltBookgt ltbtitlegtMy Favorite
Booklt/btitlegt ltISBNgt1-34567-04-01lt/ISBNgt ltAuthors
gt ltAuthorNamegtJohn Smithlt/AuthorNamegt ltAuthorN
amegtPeter Chenlt/AuthorNamegt lt/Authorsgt ltPricegt
45.00lt/Pricegt ltDescriptiongtThis is a grerat
booklt/Descriptiongt lt/Bookgt ltBookgt ltbtitlegtMy
Second Favorite Booklt/btitlegt ltISBNgt1-34567-04-02lt
/ISBNgt ltAuthorsgtAdam Smithlt/Authorsgt ltPricegt
25.00lt/Pricegt ltDescriptiongtThis is a second
great booklt/Descriptiongt lt/Bookgt lt/Booksgt
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btitle displayblock font-family Aerial,
Helvetica font-weight bold font-size
20pt color 9370db text-align
center ISBN displayblock font-family
Aerial, Helvetica font-weight
bold font-size 12pt color
c71585 text-align left Authors display
inline font-family Aerial, Helvetica font-sty
le italic font-size 10pt color
9370db text-align left
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Price displayblock font-family Aerial,
Helvetica font-size 12pt color
ff1010 text-align left Description
displayblock font-family Aerial,
Helvetica font-size 12pt color
ff1010 text-align left
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Demo

• ASPNet/FavoriteBook.htm

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Styling XML with XSLT

• XSLT Extensible Stylesheet Language Transforms
• XSLT provides a means of transforming one XML
  document into HTML or another XML document.

22
Creating XML From DataSet

• DataSet object
• WriteXML(xml file path and name)
• WriteXMLSchema(xml schema path and name)
• DemoASPNet/XMLWrite.ASPX

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dim strConn as string "ProviderMicrosoft.Jet.OLE
DB.4.0Data Source c\sales2k.mdb" dim objConn
as new OledbConnection(strConn) dim strSQL as
string "select from customer" dim objDataSet
as new Dataset() dim objAdapter as new
OledbDataAdapter(strSQL, objConn) objAdapter.Fill(
objDataSet, "Cust") dim objDataView as new
DataView(objDataSet.tables("Cust")) dgCustomer.Dat
asourceobjDataView dgCustomer.DataBind() objDataS
et.writeXML("c\inetpub\wwwroot\testWriteXML.XML")

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Reading Data into a DataSet from an XML File

• Dataset object
• ReadXMLSchema(file path and name)
• ReadXML(file path and name)
• Demo ASPNet/XMLRead.aspx

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dim objDataSet as new Dataset() objDataSet.ReadXML
("c\inetpub\wwwroot\testWriteXML.XML") dim
objDataView as new DataView(objDataSet.tables("Cus
t")) dgCustomer.DatasourceobjDataView dgCustomer
.DataBind() end sub
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XML Query Languages

• X-Query
• XPath
• SQL/XML