BSc Computer Science QM3

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BSc Computer ScienceQM3
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Course Aim Learning Outcome

• The aim of this course is to provide a practical
  overview of different elements in multimedia.

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Course Topics

• Semester 1
• Introduction to the Internet
• Introduction to Markup Languages
• Planning your website
• XHTML Authoring

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Semester 2 3

• Image processing
• color modes
• pixel point pixel group processing
• Sound for multimedia
• digital sound
• Sound synthesis

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Semester 3

• Putting it all together.
• An introduction to the Pure Data programming
  language.
• The use of sensors and microcontrollers in
  interactive multimedia.

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Lectures

• From 7 to 10pm in room 20 in westland square
• Time will normally be split between lecture and a
  computer LAB.

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Course website

• www.cs.tcd.ie/Nicholas.Ward/qm3/index.htm

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What is the Internet?

• The largest computer network in the world.
• Actually a network of networks a collection of
  more than 200,000 individual computer networks
  owned by governments, universities, non profit
  groups, and companies.

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What is the Internet?

• These interconnected networks can communicate
  because they all use the same, non proprietary
  standards and protocols.
• They are connected via high-speed long-distance
  backbone networks.

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What is the Internet?

• The Internet has opened up exciting new
  possibilities that challenge traditional ways or
  interacting, communicating, and doing business.
• Electronic networks form the key infrastructure
  of the twenty-first century, as critical to
  business success and national economic
  development as the railroads were in Morses era
  Alvin Toffler, Powershift

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Evolution of the Internet

• Began as one network ARPANET.
• A 1969 US govt. experiment in packet-switched
  networking.
• ARPA Department of Defence Advanced Research
  Projects Agency.

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Evolution of the Internet

• Originally linked a largely technical audience
  composed of the military, government agencies,
  and academic researchers and scientists.
• Aim to allow researchers to share computing
  resources and exchange information regardless of
  their locations, and to create a resilient
  fault-tolerant, wide area network for military
  communications.

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Evolution of the Internet

• ARPANET split into 2 networks in the early 1980s
  ARPANET and Milnet (an unclassified military
  network), but connections allowed communication
  to continue.
• Cooperative, decentralised networks such as UUCP
  (a worldwide UNIX communications network) and
  USENET (Users Network) originated in the late
  70s.

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Evolution of the Internet

• These initially served the academic community but
  later catered for commercial organisations.
• In the early 80s more networks such as the
  Computer Science Network (CSNET) began providing
  networking to the academic and research
  communities.

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Evolution of the Internet

• These networks were not part of the Internet, but
  special connections were made to allow the
  exchange of information between the networks.
• The National Science Foundation Network (NSFNET)
  originated in 1986 and linked researchers with
  five supercomputer centres.

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Evolution of the Internet

• The seamless internetworking of all these
  networks gave rise to the Internet we know today.
• Where Wizards Stay Up Late The Origins of the
  Internet by Katie Hafner, Matthew LyonTouchstone
  Books ISBN 0684832674 Reprint edition (January
  1998)

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The Infrastructure of the Internet

• Although the Internet began as a government
  project commercial communications companies now
  largely provide the physical network backbone of
  the internet.
• The Internet infrastructure is supplied by
  network providers, such as UUNET, an MCI WorldCom
  company, GTE Internetworking, Sprint and others.

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The Infrastructure of the Internet

• Businesses and individual subscribers connect to
  the Internet through these and other, smaller
  Internet service providers.
• Both backbone and access providers are referred
  to as Internet Service Providers (ISPs).
• These charge customers for various combinations
  of bandwidth, traffic, and access time.

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The Infrastructure of the Internet

• Backbone providers are connected to one another
  and to access providers over backbone networks.
• The various back bone networks that make up the
  Internet transmit information to one another on a
  reciprocal basis i.e. each carrier agrees to
  transport traffic originating on another
  carriers network.

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The Infrastructure of the Internet

• Historically this has been done without charge
  although this is now changing due to growing
  demands.
• Example Suppose Fred in New York wants to send
  an e-mail to Susan across the Internet. Fred is a
  customer of ZIP a small ISP, and Susan is a
  customer of another ISP.

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The Infrastructure of the Internet

• Step 1 To connect its customers to the Internet,
  Zip contracts with a company that links Zip to
  the rest of the Internet. Zip chooses one of the
  smaller companies, Frontier.
• Spep 2 Zip sends its traffic to Frontier, but
  Frontiers network is not linked to Susans ISP,
  so Frontier needs to contract with another
  Internet carrier to route Freds e-mail. There
  are two ways that Frontier can connect to another
  carrier as a peer or as a customer.

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The Infrastructure of the Internet

• Step 3 If two Internet carriers decide that they
  are peers they exchange traffic with each other
  for free. They do this either by connecting their
  networks directly or by linking at a public
  peering point (where dozens of Internet carriers
  set up their communications equipment side by
  side and share traffic).

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The Infrastructure of the Internet

• Step 4 If one Internet backbone provider is not
  accepted as a peer by another, the rejected
  company has to become a customer in order to send
  data across the other companys network.

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• Fred

Zip
Frontier
Public peering
Peer
customer
Public peering point
Public peering
MCI
Frontier
Peer
Peer
Peer
ISP
WorldCom
Sprint
Peer
Susan
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The Operation of the Internet

• Packet Switching Breaks up blocks of text into
  small, fixed bundles of data called packets.
• Each packet travels independently through the
  network
• Packets of data originating at one source can be
  routed through different paths in the network,
  and then reassembled into the original message
  when they reach their destination.

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The Operation of the Internet

• TCP/IP The set of rules used to send and receive
  packets from one machine to another over the
  Internet.
• TCP (Transmission Control Protocol) Converts
  messages to packets at source and reassembles
  them at destination.
• IP Internet Protocol Handles the addressing,
  ensures packets can be switched across multiple
  nodes.

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Addresses on the Internet

• Each computer on the Internet has an assigned
  address know as an IP(Internet Protocol) Number -
  a set of 4 numbers in the range 0 - 255
  xxx.xxx.xxx.xxx
• (e.g. 135.62.128.91)
• Most computers also have names (easier to
  remember). These are derived from the domain name
  system (DNS).

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Addresses on the Internet

• DNS is a collection of servers on a TCP/IP
  network.
• Resolves the text names used with the numberical
  IP address that computers use.
• Arranged as a hierarchical database, with
  authority for naming handed from root servers
  responsible for top level domains down to lower
  sub-domains.

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Addresses on the Internet

• All Internet destinations that can be found by
  name require an entry on a DNS server.
• This process is the foundation for message
  delivery and navigation on the Internet.

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Addresses on the Internet

• Stages
• Request for an Internet name is submitted to a
  DNS server.
• Server checks its info and attempts to respond
  with appropriate IP Number.
• If server cant respond, request directed to one
  of the top level DNS servers.
• Request sent down the Domain Name System
  hierarchy
• Response sent to request originator when an
  authoritative DNS for the domain and the machine
  are found.

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Addresses on the Internet

• Domain names consist of multiple parts.
• Eg. software.ibm.com com (the rightmost part
  of the name) is the name of the top-level
  specification/domain or the zone.
• For a list of top level domains
  http//www.iana.org/domain-names.htm

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Services Provided by the Internet

• Communications Services
• E-mail
• USENET Newgroups/forums A protocol that
  delineates how groups of messages can be stored
  on and sent between computers. International
  discussion groups in which people share
  information and ideas on a particular topic.

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Services Provided by the Internet

• LISTSERV When e-mail is addressed to a LISTSERV
  mailing list, it is automatically broadcast to
  everyone on the list. The result is similar to a
  newsgroup or forum, except that the messages are
  transmitted as e-mail and are therefore available
  only to individuals on the list.
• Chatting Allows two or more people who are
  simultaneously connected to the Internet to hole
  live (real-time) interactive written
  conversations. Internet relay chat (IRC) is a
  general chat program for the Internet

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Services Provided by the Internet

• Instant Messaging A type of communications
  service that enables you to create a private chat
  room with another individual. Typically, the
  instant messaging system alerts you whenever
  somebody on your private list is online. You can
  then initiate a chat session with that particular
  individual.
• Telnet Allows users to be on one computer while
  doing work on another. A protocol that
  establishes an error-free link between the two
  computers.

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Services Provided by the Internet

• Internet Telephony A category of hardware and
  software that enables people to use the Internet
  as the transmission medium for telephone calls.
  Lets users talk across the Internet to any
  personal computer equipped to receive the call
  for the price of only the Internet connection.
  Also called Voice over IP or VoIP)
• Internet Fax The use of the Internet for
  real-time fax transmissions. Useful because faxes
  can be sent long distance at local telephone
  rates delivery can be guaranteed through store
  and forward mechanisms.

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Services Provided by the Internet

• Streaming Audio and Video Streaming allows
  Internet users to see and hear data as it is
  transmitted from the host server instead of
  waiting until the entire file is downloaded.
• Real-Time Audio and Video The transmission from
  the source is live or only slightly delayed. E.g.
  video conferencing, live broadcasts of news etc.

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Services Provided by the Internet

• Information Retrieval Services
• File Transfer Protocol (FTP) Enables users to
  access a remote computer and retrieve files from
  it.
• Archie A tool that allows users to search the
  files at FTP sites. It regularly monitors
  hundreds of FTP sites and updates a database
  (called an Archie server) on software, documents,
  and data files available for downloading.

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Services Provided by the Internet

• Gophers A system that pre-dates the World Wide
  Web for organizing and displaying files on
  Internet servers. A Gopher server presents its
  contents as a hierarchically structured list of
  files. With the ascendance of the Web, most
  Gopher databases are being converted to Web sites
  which can be more easily accessed via Web search
  engines.
• Veronica (Provides the capability for searching
  for text that appears in gopher menus

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The World Wide Web

• Not the same as the Internet. The Internet
  functions as the transport mechanism, and the
  World Wide Web (the Web, WWW, or W3) is an
  application that uses those transport functions.
• A system with universally accepted standards for
  storing, retrieving, formatting, and displaying
  information via a client/server architecture.
• Handles all types of digital information text,
  graphics, sound, etc. Uses a graphical user
  interface v.easy to use.

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Introduction to the Web Model

• 4 essential concepts you need to understand
• Uniform Resource Locators, or URLs
• The Hypertext Transfer Protocol (HTTP)
• Hypertext Markup Language, or HTML/XHTML
• Cascading Stylesheets, or CSS

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Uniform Resource Locators / URLs

• To access a Web site, the user must specify a
  uniform resources locator (URL), which points to
  the address of a specific resource on the web.
• URL the global address of documents and other
  resources on the World Wide Web.
• Refers to a naming scheme for specifying how and
  where to find any Internet resource, such as
  those available from HTTP, FTP, or news servers.

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Uniform Resource Locators / URLs

• Eg. The URL that references the important file
  bunny_hop.html in the directory pub/web/browsers
  on the HTTP server www.w3.org is simply
  httpwww.w3.org/pub/web/browsers/bunny_hop.html.
• The prefix http references the fact that the
  resource is on a http server while the remaining
  part defines the resource being requested (e.g
  the file bunny_hop.html) and also often names the
  location (including the name of the computer) of
  the resource.
• So A URL names where a resource is on the
  Internet and how to get it.

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Hypertext Transfer Protocol (HTTP)

• Hypertext Transfer Protocol (HTTP) the
  communications standard used to transfer pages
  across the WWW portion of the Internet. It was
  designed expressly for the rapid distribution of
  hypertext documents.
• It defines how messages are formatted and
  transmitted and what actions web servers and
  browsers should take in response to various
  commands.

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Hypertext Transfer Protocol (HTTP)

• HTTP servers are designed specifically to
  distribute hypertext documents to browsers and
  also to let the browser send back information for
  processing on the server.
• Like most other Internet tools, HTTP is a
  client-server protocol. In the client-server
  model a client program (the web browser) running
  on the users machine, sends a message requesting
  service to the server program running on another
  machine on the internet. The server responds to
  the request by sending a message back to the
  client.

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Hypertext Transfer Protocol (HTTP)

• In exchanging these messages the client and
  server use a mutually-understood protocol.
• FTP and News are other examples of Internet
  client-server protocols all of which are
  accessible to a WWW browser. However the HTTP
  protocol was designed expressly for hypertext
  document delivery.

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HyperText Markup Language (HTML)

• A standard hypertext language which formats
  documents and incorporates hypertext links to
  other documents stored on the same or different
  computers.
• This is the markup language with which the WWW
  hypertext documents are written.

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HyperText Markup Language (HTML)

• HTML contains commands, called elements or tags
  to mark text as headings, paragraphs, lists,
  quotations, and so on. It also has tags for
  including images within the documents, for
  including fill-in forms that accept user input,
  and, most importantly, for including hypertext
  links connecting the document being read to other
  documents or Internet resources.
• Recently, the HTML language has been revised and
  renamed XHTML. This is almost the same as HTML
  but is designed to work with new software based
  on another language called the eXtensible Markup
  Language (XML).

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Cascading Stylesheets (CSS)

• These control page layout and formatting.
• The markup language (HTML or XHTML) doesnt
  actually define how a document should look.
• Browsers that display such documents generally
  have built in rules for how things should look,
  but these rules are very simple and hard to
  modify. As a result it is hard to create web
  pages that have elegant designs and layouts
  without using all sorts of special tricks and
  images to get things looking the way you want.

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Cascading Stylesheets (CSS)

• CSS works with HTML to define how things should
  look. While HTML and XHTML are languages that
  describe the structure of a document, CSS defines
  how these parts should be styled and can control
  things like borders, margins, font properties,
  position and so on.

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Designing and Developing Web Pages

• Designing and Developing good web pages involves
  both technical issues (proper construction of the
  document) and design issues (ensuring the
  information content is clearly presented to the
  user).
• This entails a good understanding of both HTML
  and CSS.

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Introduction to Markup Languages

• Historically, the word markup has been used to
  describe annotation or other marks within a text
  intended to instruct a compositor or typist how a
  particular passage should be printed or laid out.
  
• Eg. wavy underlining to indicate boldface,
  special symbols for passages to be omitted or
  printed in a particular font and so forth.

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Introduction to Markup Languages

• As the formatting and printing of texts was
  automated, the term was extended to cover all
  sorts of special markup codes inserted into
  electronic texts to govern formatting, printing,
  or other processing.
• Generalizing from that sense, we define markup as
  any means of making explicit an interpretation of
  a text.

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Introduction to Markup Languages

• By markup language we mean a set of markup
  conventions used together for encoding texts.
• A markup language must
• Specify what markup is allowed.
• What markup is required
• How markup is to be distinguished from text
• What the markup means.

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SGML

• SGML is an international standard for the
  description of marked-up electronic text.
• More exactly, SGML is a metalanguage, that is, a
  means of formally describing a language, in this
  case, a markup language.

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SGML

• SGML allows you to define your own tags, each of
  which is used to mark a particular sort of
  document element, such as a paragraph, section
  heading or a list.
• In SGML defining a tag consists of giving it a
  name and some attributes and specifying some
  restrictions on the context in which the tag can
  be used.

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SGML

• In SGML the structure of a document is defined in
  the Document Type Definition (DTD) .
• A DTD describes how a document can be structured.

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Introduction to SGML
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Elements

• The technical term used in the SGML standard for
  a textual unit, viewed as a structural component,
  is element.

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• Within a marked up text (a document instance),
  each element must be explicitly marked or tagged
  in some way.
• The standard provides for a variety of different
  ways of doing this, the most commonly used being
  to insert a tag at the beginning of the element
  (a start-tag) and another at its end (an
  end-tag).

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• The start- and end-tag pair is used to bracket
  off the element occurrences within the running
  text, in rather the same way as different types
  of parentheses or quotation marks are used in
  conventional punctuation.
• For example, a quotation element in a text might
  be tagged as follows

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• ... Rosalind's remarks This is the
  silliest stuff that ere I heard of!
  clearly indicate ...

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• As this example shows, a start-tag takes the form
  , where the opening angle indicates the start of the start-tag,
• name'' is the generic identifier of the
  element which is being delimited, and the closing
  angle bracket indicates the end of a tag.
• An end-tag takes an identical form, except that
  the opening angle bracket is followed by a
  solidus (slash) character, so that the
  corresponding end-tag would be .

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• The actual characters used for the delimiting
  characters (the angle brackets, exclamation mark
  and solidus) may be redefined, but it is
  conventional to use the characters used in this
  description.

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SGML An Example

• An element may be empty, that is, it may have no
  content at all, or it may contain simple text.
  More usually, however, elements of one type will
  be embedded (contained entirely) within elements
  of a different type.

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• An Example
• Consider a very simple structural model. Let us
  assume that we wish to identify within an
  anthology only poems, their titles, and the
  stanzas and lines of which they are composed.

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• In SGML terms, our document type is the
  anthology, and it consists of a series of poems.
• Each poem has embedded within it one element, a
  title, and several occurrences of another, a
  verse,\
• each verse having embedded within it a number of
  line elements.

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• Fully marked up, a text conforming to this model
  might appear as follows

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• The SICK ROSE
• O Rose thou art sick.
• The invisible worm,
• That flies in the night
• In the howling storm

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• Has found out thy bed
• Of crimson joy
• And his dark secret love
• Does thy life destroy.

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• Considering our greatly over-simplified model of
  a poem, we could state the following rules

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• An anthology contains a number of poems and
  nothing else.
• A poem always has a single title element which
  precedes the first verse and contains no other
  elements.
• Apart from the title, a poem consists only of
  verses.
• Verses consist only of lines and every line is
  contained by a verse.
• Nothing can follow a verse except another verse
  or the end of a poem.
• Nothing can follow a line except another line or
  the start of a new verse.

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• The SICK ROSE
• O Rose thou art sick.
• The invisible worm,
• That flies in the night
• In the howling storm

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• Has found out thy bed
• Of crimson joy
• And his dark secret love
• Does thy life destroy.

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• Before considering these rules further, you may
  wish to consider how text marked up in the form
  above could be processed by a computer for very
  many different purposes.

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• A simple indexing program could extract only the
  relevant text elements in order to make a list of
  titles, or of words used in the poem text.
• A simple formatting program could insert blank
  lines between stanzas, perhaps indenting the
  first line of each, or inserting a stanza number.
  
• Different parts of each poem could be typeset in
  different ways.

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EXAMPLE DTD

• A DTD is expressed in SGML as a set of
  declarative statements, using a simple syntax
  defined in the standard. For our simple model of
  a poem, the following declarations would be
  appropriate

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An Example DTD

• verse)

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• These five lines are examples of formal SGML
  element declarations.
• Each consists of three parts
• a generic name
• two characters specifying minimization rules
• a content model.
• Components of the declaration are separated by
  white space, that is one or more blanks, tabs or
  newlines.

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• The first part of each declaration gives the
  generic identifier of the element which is being
  declared, for example poem, title, etc.

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Minimization Rules

• determine whether or not start and end tags must
  be present in every occurrence of the element
  concerned.
• They take the form of a pair of characters,
  separated by white space, the first of which
  relates to the start-tag, and the second to the
  end-tag. In either case, either a hyphen or a
  letter O (for omissible'' or optional'') must
  be given

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• The hyphen indicates that the tag must be
  present,
• The letter O that it may be omitted.
• In this example, every element except must
  have a start-tag. Only the and
  elements must have end-tags as well.

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Content Model

• specifies what element occurrences may
  legitimately contain.
• Contents are specified either in terms of other
  elements or using special reserved words.
• There are several such reserved words, of which
  by far the most commonly encountered is PCDATA,
  as in this example. This is an abbreviation for
  parsed character data, and it means that the
  element being defined may contain any valid
  character data.

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• But wait theres more!
• The content model has other bits in it.

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Occurrence Indicators

• Indicates how many times the element named in its
  content model may occur. There are three
  occurrence indicators in the SGML syntax,
  conventionally represented by the plus sign, the
  question mark, and the asterisk or star.

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• Occurrence indicators
• The plus sign means that there may be one or more
  occurrences of the element concerned.
• The question mark means that there may be at most
  one and possibly no occurrence.
• The star means that the element concerned may
  either be absent or appear one or more times.

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Group Connectors

• The content model (TITLE?, VERSE) contains more
  than one component, and thus needs additionally
  to specify the order in which these elements (
  and ) may appear. This ordering is
  determined by the group connector (the comma)
  used between its components.

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• There are three possible group connectors
• The comma means that the components it connects
  must both appear in the order specified by the
  content model.
• The ampersand indicates that the components it
  connects must both appear but may appear in any
  order.
• The vertical bar indicates that only one of the
  components it connects may appear.

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Attributes

• In the SGML context, the word attribute, like
  some other words, has a specific technical sense.
  It is used to describe information which is in
  some sense descriptive of a specific element
  occurrence but not regarded as part of its
  content.

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For example

• ...

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• An SGML processor can use the values of the
  attributes in any way it chooses
• A formatter might print a poem element which has
  the status attribute set to draft in a different
  way from one with the same attribute set to
  revised.
• Another processor might use the same attribute to
  determine whether or not poem elements are to be
  processed at all.

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• Attributes
• Like elements, attributes are declared in the
  SGML document type declaration (DTD), using
  rather similar syntax.
• As well as specifying its name and the element to
  which it is to be attached, it is possible to
  specify (within limits) what kind of value is
  acceptable for an attribute and a default value.

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• The following declarations could be used to
  define the two attributes we have specified above
  for the element
• id ID IMPLIED
• status (draft revised published)
  draft

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• The declaration begins with the symbol ATTLIST,
  which introduces an attribute list specification.
  
• The first part of this specifies the element (or
  elements) concerned. In our example, attributes
  have been set for poem

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• Following this name (or list of names), is a
  series of rows, one for each attribute being
  declared, each containing three parts
• The name of the attribute
• The type of value it takes
• A default value respectively.

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SGML

• If a DTD describes a sufficiently large class of
  documents it may make sense to construct display
  software specifically for that class of document
  and to hardwire the layout rules into the
  software.
• That way every document will be laid out
  consistently by a particular display program.

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Markup Languages

• This is the approach followed by the first
  generation of web browsers.
• Most of the formating of headers, lists, tables
  and other elements is controlled by the browser,
  but some details, specifically fonts, type sizes
  and colours, may be controlled by preferences set
  by the user.

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Markup Languages

• Alternative option Provide a separate
  specification of the layout, parallel to and
  complementing the DTD.
• This layout specification is known as a
  stylesheet.
• For each tag defined in the DTD, a stylesheet
  provides a rule describing the way in which
  elements with that tag should be laid out.

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Markup Languages and the WWW

• Since structural markup can be interpreted on any
  platform in a logically consistent if not
  necessarily visually consistent manner, it is
  ideally suited for the markup of documents which
  are to be transimitted over networks.
• When the World Wide Web was being designed SGML
  was used as the basis of the Hypertext Markup
  Language (HTML).

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HTML

• HTML provides a set of tags suitable for marking
  up web pages.
• It does not provide any way of defining new tags.
• HTML is defined by an SGML DTD, which describes
  the structure of the class of documents known as
  Web pages.
• Like SGML it is concerned solely with identifying
  the structural elements of a page and not with
  their appearance.

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HTML

• Originally the WWW was intended as a means of
  dissemination of scientific research, so the DTD
  for the Web pages contained tags corresponding to
  the main elements of a scientific paper
• Title
• Headings that can be nested several levels deep
• Lists of various types
• Some typographical control (bold, italic)
• Tables
• Forms
• Etc.

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HTMLs Limitations

• Although adequate for marking up simple mainly
  textual papers for which they were originally
  intended, HTMLs layout tags are not sufficient
  for all the diverse types of material which have
  found their way onto the WWW.
• Two results
• Browser manufacturers added ad hoc proprietary
  extensions to HTML.
• Web Designers used tags as they were never
  intended.

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XML

• Solution provide web designers with a facility
  to define their own tags.
• SGML can do this, but too unwieldy, slow response
  times.
• Work on adapting SGML to the Internet led to the
  definition of a subset, known as XML (eXtensible
  Markup Language).

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XML

• Provides all of the important facilities of SGML
  without the overhead imposed by full SGML.
• XML allows web designers to define their own DTDs
  for any type of document.
• All new browsers now read and interpret (parse)
  both HTML and XML but as XML becomes the new
  standard HTML will be left in the lurch.

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XHMTL 1.0

• XHTML is an XML-based language that reproduces
  essentially all the features of HTML, subject to
  the stricter syntax of XML.
• XHTML documents can be processed by both HTML and
  XML software. So XHTML documents can be read by
  existing HTML browsers of can be used with future
  browsers that understand XML.

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SGML and XML Family Tree
SGML

• XML

HTML
XHTML
MathML
SMIL
SVG
107

• PHEW!