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SGML

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October '94: Tim Berners-Lee founded World Wide Web Consortium (W3C) ... Values for attributes are enclosed in quotes. Example: ... – PowerPoint PPT presentation

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Title: SGML


1
SGML
  • SGML stands for
  • Standard Generalized Markup Language
  • In 1960, three IBM employees were exploring a way
    to interchange documents of different file
    formats
  • Solution System-independent common format
  • Use a mark-up language
  • How?
  • Identify a structure of a document
  • In 1974, IBM employee found a way to analyze the
    structure and syntax of a document
  • i.e. parser
  • In 1986, SGML was adopted as an international
    standard

2
HTML
  • In 1989, Tim Berners-Lee began exploring a way to
    develop a technology for sharing information
    using hyperlinked text documents
  • He based this technology on SGML and called it
    HyperText Markup Language (HTML)

3
W3C
  • October 94 Tim Berners-Lee founded World Wide
    Web Consortium (W3C)
  • Aim develop interoperable technologies
  • Make the web universally accessible regardless of
    language, culture, etc
  • W3C serves as a standardization organization.
  • Web technologies standardized by W3C are called
    Recommendations
  • Current Recommendations include
  • HTML, CSS, XML, etc

4
W3C continued
  • What are recommendations?
  • They are not an actual software
  • Documents that specify the role, syntax, rules,
    etc.., of a technology (i.e. HTML)
  • W3C is inspired by
  • MIT (USA)
  • INRIA (France),
  • Keio University (Japan), and
  • other members

5
What is DTD?
  • The document type definition (DTD) is the method
    used to define all markup languages.
  • DTD specifies the syntax (grammatical structure)
    of a web page
  • While HTML predefines set of tags guaranteed to
    be understood and displayed in a uniform fashion
    in a web browser, XML allows the document creator
    to define any set of tags he or she wishes to.
  • This set of tags is grouped into a set of rules
    known as the Document Type Definition.

6
Cascading Style Sheets (CSS)
  • CSS enables you to specify the style of your page
    elements
  • i.e. spacing, margins, mouse-over colors, etc
  • separately from the structure of a document
  • Advantage
  • Separate structure from presentation
  • Manageability
  • Changing style of a document is more dynamic

7
Cascading Style Sheets (CSS)continued
  • Declaring styles in a document
  • Inline Style
  • within an element (i.e. HTML elements)
  • Style Element
  • through style element (i.e. apply to all elements
    within a document)
  • External document
  • Linking an external style sheet

8
eXtensible Markup Language(XML)
  • XML is a technology that allows developers to
    describe data of any type in a structured manner
  • XML, unlike HTML, allows authors to describe data
    more precisely by creating new tags.
  • XML serves as basis for creation of other markup
    languages (i.e. WSDL) used for describing data

9
eXtensible Markup Language(XML) continued
  • Sample XML document i.e. books.xml
  • lt?xml version "1.0"?gt
  • ltBooksgt
  • ltBookgt
  • ltISBNgt0596007647lt/ISBNgt
  • ltAuthorgtElliotte Rusty Harold, W. Scott Means
    lt/Authorgt
  • ltTitlegtXML in a Nutshell, Third Edition lt/Titlegt
  • ltPublishergtO'Reilly Media, Inclt/Publishergt
  • lt/Bookgt
  • lt/Booksgt

10
eXtensible Markup Language(XML) continued
  • lt?xml version "1.0"?gt
  • ltBooksgt
  • ltBookgt
  • ltISBNgt0596007647lt/ISBNgt
  • ltAuthorgtElliotte Rusty Harold, W. Scott Means
    lt/Authorgt
  • ltTitlegtXML in a Nutshell, Third Edition lt/Titlegt
  • ltPublishergtO'Reilly Media, Inclt/Publishergt
  • ltEdition ver2/gt
  • lt/Bookgt
  • lt/Booksgt

root element
opening tag
empty tag
closing tag
attribute value
attribute
11
eXtensible Markup Language(XML) continued
  • A software called XML Parser is required for
    processing XML documents.
  • XML Parser
  • Reads XML document
  • Checks the syntax
  • Reports any errors
  • XML is case sensitive !

12
eXtensible Markup Language(XML) continued
  • For accessing XML documents, parsers can support
  • Document Object Model (DOM)
  • Builds a tree structure containing the XML
    documents data in memory
  • Simple API for XML (SAX)
  • When text, comments etc.. are processed, the SAX
    generates events in the form of data
  • i.e. notifications to the applications

13
eXtensible Markup Language(XML) continued
  • Parsing with MSXML
  • When a document is loaded into IE, the document
    is processed and parsed by msxml.
  • If the document is free of errors, the parser
    makes the documents data available to the
    application (i.e. IE).
  • The application can render and format the data
    and performs other processing.

14
eXtensible Markup Language(XML) continued
  • When books.xml is loaded into IE, the msxml
    parses the XML document and makes the data
    available.
  • A stylesheet that formats and colors the markup
    almost identically to the original document is
    used.

15
eXtensible Markup Language(XML) continued
  • IE output

16
eXtensible Markup Language(XML) continued
  • Firefox output

17
eXtensible Markup Language(XML) continued
  • Markup
  • ltimg srctest.gifgt
  • In HTML, this code is correct, but in XML it is
    not. The ending tag must also be supplied
  • ltimg srctest.gifgtlt/imggt
  • This type of element is called empty element
    because it does not contain any content (i.e.
    data between the tags). Alternatively, empty tags
    can be written as
  • ltimg srctest.gif/gt
  • forward slash for termination

18
eXtensible Markup Language(XML) continued
  • Elements define structure
  • An element may or may not contain content
  • Attributes describe elements
  • i.e. ltimg src width heightgt
  • An element may have zero, one, or more
    attributes.
  • Attributes are placed within the elements start
    tag
  • Values for attributes are enclosed in quotes
  • Example
  • ltBookInfo authorSome Name isbn 1223232
    publisherOReillygt

19
eXtensible Markup Language(XML) continued
  • CDATA Sections
  • These are sections that can contain text,
    reserved characters, and whitespace characters.
  • Character data in the CDATA section are not
    processed by the XML parser.
  • Common use for CDATA is JavaScript, VBScript,
    etc

Whitespace characters are Spaces, tabs, and
carriage returns are characters commonly
20
eXtensible Markup Language(XML) continued
  • Namespaces
  • Since authors have the ability to create their
    own tags, a collision can occur
  • Collision two different elements having the same
    name
  • Namespaces provides authors with the means to
    prevent collisions

21
MathML
  • Presenting mathematical expressions and equations
    in web documents is usually difficult
  • Most systems support only the basic symbols for
    operators such as ,-,, /
  • MathML, the Math Markup Language, meets the needs
    of a broad set of users including scientists,
    teachers, publishing industry, etc
  • MathML allows you to create and manipulate
    mathematical expressions

22
VoiceXML
  • VoiceXML is used to define voice catalogs
  • i.e. interactive phone-based banking system for
    accessing account
  • i.e. Registering for services
  • i.e. Checking your balance
  • VoiceXML uses interactive voice systems that read
    content to you loud over the phone.
  • It relies on infrastructure like the Internet
    Interactive Voice Response (IVR) devices, and
    VoiceXML gateways to deliver content.
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