Multimedia in Organisations

1
Multimedia in Organisations

• BUSS 213

Lecture 11 Delivery Approaches Magnetic/Optical
Internet and Hybrid
2
Notices General

• Marking is not complete for Assignment 2- should
  be available Tuesday this coming week
• Will student 2147816 see Dr. L. Schafe concerning
  Assignment 2
• Students must be allocated to A3 Groups today-
  make sure I know which group you are in
• this week we will discuss storyboarding in
  tutorials- you will work on assignment
• BUSS213 website where you can find out the latest
  Notices and get Lecture Notes, Tutorial Sheets,
  Assignments etc is
• www.uow.edu.au/rclarke/buss213/buss213.htm

3
Agenda (1)

• in this lecture we examine modes of delivery for
  multimedia in this lecture
• so far in this course we have assumed that
  multimedia systems are delivered to users by
  means of magnetic/optical storage (primarily
  CD-ROMs)
• however in this lecture we emphasise what is and
  will continue to be arguably the most common form
  of multimedia delivery- the Internet- and more
  particularly the WWW

4
Agenda (2)

• the Internet and WWW provides unique
  opportunities for multimedia developers as well
  as posing real problems- is is very complex
  requiring mastery of a large number of disparate
  technologies server-side and client side
• the web provides the possibility of having some
  content especially in the form of text resources
  updatable over time
• unfortunately video and other resource intensive
  temporal media dont work well over the net
• this has resulted in the development of web-based
  or so-called hybrid multimedia systems in which
  users have CD-ROMs full of video content, indexed
  by web pages served across the internet

5
Agenda (3)

• I consider hybrid multimedia systems to be no
  different to other web applications but they have
  surprising effects on content
• rather than thinking of the content in a
  multimedia system as static- we can think of
  content as a process- as evolving- this really
  does lend itself to the creation of
  organisational multimedia
• Unlike the usual educational multimedia systems
  that are developed- we arent playing games any
  more!

6
Agenda (4)

• we describe web technology especially
• web clients and servers
• how servers actually serve up pages
• what other operations they perform
• the concept of web applications
• the concept of dynamic websites

7
Related Readings

• Vaughan (1998) Chapter 18 Designing for the
  World Wide Web, 495-520
• Vaughan (1998) Chapter 20 Delivering, 543-568

8
Web Clients ServersSource Yeager McGrath
(1996, 11-16)
9
Internet

• Internet (Internetworking) collection of
  computer networks and to allow interoperability
  between them
• networks can consist of many types of network
  technologies, protocols, and computers
• Several protocols are required for transmitting
  data across the Internet (TCP/IP)

10
InternetInternet Protocol

• IP manages the transfer of data across physically
  distinct networks
• transfers data into packets within an envelope
  that describing its source and destination
• a message is in effect shattered into pieces,
  packaged as packets in envelopes, and burst
  transmitted to the destination
• IP looks after delivering these packages- one
  packet at a time!

11
InternetTransmission Control Protocol

• networks are unreliable and IP does not guarantee
  that all pieces arrive (no notion of a
  connection)
• TCP defines conventions that make sure the pieces
  arrive in the correct order- by specifying
  another envelope around the data packets
• IP layer moves packets, TCP manages the connection

12
InternetOther Services Protocols

• the layering or encapsulation which is a
  characteristic of OSI also works in much the same
  way with other services supported by the Internet
  (TCP/IP)
• File Transfer Protocol defines the conventions
  which describe how computers can cooperate in
  order to copy files from one computer to another
  on the Internet- it uses TCP/IP to do this

13
InternetOther Services Protocols
Internet Protocol Transmission Control Protocol
File Transfer Protocol
FTP
FTP
TCP
TCP
Physical Network
14
InternetWeb Services Protocols

• the web is just another internet service!
• Hypertext Transfer Protocol (HTTP) is the set of
  rules for making and fulfilling web requests
• however, the web is also designed to encapsulate
  other protocols including FTP, Gopher, WAIS,
  telnet and NNTP- we will talk about these
  services latter

15
InternetWeb Services

• works as a client-server- in terms of services
  not necessarily hardware
• differs from other network models (terminal to
  mainframe and peer-to-peer) because client and
  server are independent, fully functional computer
  systems in their own right

16
InternetWeb Services
email
17
Intranets OASuccess of WWW- Open Standards

• machines on the Internet are effectively
  decentralised
• an important aspect of the web is that it is a
  set of open (not proprietary) protocols
• Uniform Resource Locators URLs
• Hypertext Transfer Protocol (HTTP)
• Hypertext Markup Language (HTML)

18
Intranets OASuccess of WWW- Specific Issues

• web protocols are general enough to be
  implemented on any computer
• web application are the topmost layer in the
  Internet protocol hierarchy
• complex processes of transfer of data are
  hidden from the web application developer and
  user
• as a consequence there is a great variety of web
  applications available

19
Web Servers ClientsSource Yeager McGrath
(1996, 11-16)
Web
Web
FTP
FTP
TCP
TCP
Physical Network
20
Serving Documents- Example
21
Serving Documents- Example 1 Server waits for a
new request

• httpd program waits for a clients request to
  arrive from somewhere on the Internet
• server listens to a port until someone calls it
  and until that occurs it is dormant

22
Serving Documents- Example2 Request arrives
from client ...

• ultimately a request is sent by a client to the
  server either by typing a URL or selecting a HTML
  anchor
• the network software (client) locates the server
  computer and sets up a 2-way network connection
  from the client to the server

23
Serving Documents- Example... 2 Request arrives
from client

• client can locate servers by the use of Internet
  protocols and the name service (DNS) to locate
  and initiate a connection with the server
• once the connection is established the client
  sends the HTTP request
• GET /sample.htm HTTP/1.0
• sent over the network in ASCII, server receives
  it and saves it

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Serving Documents- Example3 server parses the
request ...

• server decodes the request using HTTP protocol to
  determine what to do
• there are three important pieces of information
• the method instructs the server as to what
  action should be taken. The GET method is used to
  locate and read the file and return it to the
  client ...

25
Serving Documents- Example... 3 server parses
the request

• the document (/sample.htm) can be fetched by the
  server because it knows where it is in the
  document tree, and the
• browser protocol being used (HTTP/1.0) so that
  the contents can eventually be returned to the
  client sent back over the same connection as the
  request. (Note that the server need not find the
  client on the Internet or make a new connection)

26
Serving Documents- Example4 Read other
information (if necessary) ...

• the httpd program reads the rest of the requests
  needed
• using HTTP/1.0 the browser is expected to send
  additional information about itself to the server
• this meta-information describes the browser and
  its capabilities which may be needed by the
  server to reply to the request

27
Serving Documents- Example... 4 Read other
information (if necessary)

• for example
• User-agent Mosaic for X Windows/2.4
• Accept text/plain
• Accept text/html
• Accept image/
• indicates the browser is Mosaic configured to
  display text, and any kind of image

28
Serving Documents- Example5 Do the requested
method ...

• Assuming no errors, the httpd program executes
  the request
• to GET a document requires looking up the file
  /sample.htm in its document tree using its
  standard operating system
• there are two alternative courses of action
  depending on sucess or failure

29
Serving Documents- Example... 5 Do the
requested method (Success) ...

• the httpd daemon sends a result code and the
  information that describes the type of
  information expected by the client
• as the document is found a code 200 (everything
  is OK) is sent and the document will follow
• the information is a HTML document so the
  Content-type text/htm the document is 1066
  bytes long so the Content-length 1066
• the server software and the file date are also
  included

30
Serving Documents- Example... 5 Do the
requested method (Success)

• the header sent to the client might look
  something like this
• HTTP/1.0 200 Document follows
• Server NCSA/1.4
• Date Thu, 20 Jul 1996 220000 GMT
• Content-type text/html
• Content-length 1066
• Last-modified Thu, 20 Jul 1996 203840 GMT

31
Serving Documents- Example5 Do the requested
method (Failure)...

• if the requested file could not be found or read
  then the status code will not be 200
• the most common problem is that the name of the
  requested file is misspelt so the server cannot
  find it
• if the requested file was called smple.htm it
  would not be found- the server would send a
  status code 403

32
Serving Documents- Example... 5 Do the
requested method (Failure)...

• the response might look like this
• HTTP/1.0 403 Not Found
• Server NCSA/1.4
• Date Thu, 20 Jul 1996 220000 GMT
• Content-type text/htm
• Content-length 0

33
Serving Documents- Example6 Finish Up

• when the file is completely sent or an error
  message is sent,
• the httpd server has finished its work- it closes
  the file if it was open, and closes the network
  port which terminates the network connection
• the client receives and formats the data- the
  server knows nothing
• the httpd server listens for another request (go
  back to step 1)

34
Web Server Operations
35
Web Server Operations

• a web server has a collection of information in a
  document tree and it serves it according to the
  HTTP protocol
• web servers are reactive programs waiting until a
  request is made it attempts to make it, this is
  repeated etc.
• the previous example is only slightly simplified

36
Web Server OperationsHandling Multiple Requests
(1)

• if a server processes one request at a time, but
  can receive many simultaneous requests then
  delays will occur- an image may take several
  seconds to serve
• without a priority scheme, small jobs that can be
  serviced quickly take inordinate amount of time
  to serve
• with a large number of hits servers can go down-
  backlog can be too great

37
Web Server OperationsHandling Multiple Requests
(2)

• web servers are therefore designed to handle as
  many requests as possible simultaneously
• several strategies are available to do this (the
  last two are are more difficult unless special
  software is used)
• clone a copy of the httpd program for each
  request- very easy under UNIX
• multithreading the httpd program
• spreading the work amongst several helper programs

38
Web Server OperationsCloning Servers (1)

• each request is processed by a new copy of the
  httpd program
• the original server called the parent immediately
  returns to listening for another request
• the new copy called the child performs the
  processing

39
Web Server OperationsCloning Servers (2)

• the parent passes the network connection to the
  adult at the time that it is first spawned
• when the has services the request, it terminates
  forever
• the web server hardware may have many copies of
  the httpd program running simultaneously

40
Web Server OperationsMultithreaded Execution

• many mechanisms can be used for implementing this
  approach
• server may monitor the progress of several
  connections, switching between them as necessary
• when a lengthy process is in operation the server
  may switch to another pending task
• when the pending processes is complete it can
  return to the previous lengthy process
• server closes the network connections of any
  finished processes
• this can be an extremely efficient method

41
Web Server OperationsServers as Cooperating Sets
of Programs

• the httpd server itself can be made a set of
  cooperating programs specialised to perform
  particular tasks
• One program reads the requests fro the network,
  another allocates them to specialised helper
  programs
• the scheme is very efficient, the number of
  helpers can be adjusted to meet the number of
  requests, the type of requests (generally less
  common) or the size of the system

42
Web Server OperationsMultiple Web Services on
the same Servers

• more than one web service can run on the same
  computer
• any number of httpd programs can run on a UNIX
  machine as long as they have a unique port number
• the following web services are on the same
  computer but different ports (the superuser sets
  up port 80 servers, but users can own and operate
  unrestricted ports above 1024)
• http//www.rods.org/index.htm (port 80)
• http//www.rods.org8080/index.htm (port 8080)
• http//www.rods.org8081/index.htm (port 8081)

43
Web Server OperationsEstablishing a Two-Way
Network Connection

• client must look up the network address of the
  server using its name
• the clients system software sends a packet back
  to the server, requesting a connection
• the servers system software sends a packet back
  to the client, agreeing to set up a connection
• the client program is connected to the new
  network connection
• the server program is connected to the new
  network connection

44
Web Applications
45
Web ApplicationsFrom Multimedia to Web

Database (MySQL)
Local (Client-side) front-end or client side may
run as an apparently standalone application
Web Server (Apache)
Database Integration (PHP)
Remote (Server-side) back-end may be a proxy or
web server (local or remote) that allows updates
for some resources
Version Control Subsystem
User Interface (BHP Project Director)
46
Web Applications

• a number of companies are implementing
  mission-critical web based applications
• these applications generally utilise databases
• attempt at developing closer alliances with
  customers, suppliers, partners, and employees
• organisational multimedia systems will
  increasingly become delivered in this form
• by using heterogeneous platforms, multimedia
  content is distributed throughout the
  infrastructure of a firm

47
Web Applications

• sophisticated web applications must support
  complex Internet/intranet system configuration
• systems level hardware/software, and networking
  products must work together
• software elements JAVA applets, Microsoft Active
  X controls, CGI scripts, SQL code

48
Web ApplicationsWeb Database Applications-
Components
External helper program
Browser Layer Application Logic Layer Databa
se Gateway Layer Database Layer
HTML Document
Java Application
Java applet
CGI program
Proprietary Web Server
Web Server API module
Vendors Database API
Command-line interface to database
JDBC
ODBC
Database (RDMS)
49
Web ApplicationsSystem Configuration Logical
View
Client Workstations with Web Browsers
Production Web Server
Application Server
Firewall
Database Server
Mainframe Database
DevelopmentWeb Server
50
Web Applications

• all real system development is complex, and web
  applications are no different to traditional
  systems development projects in that respect
• however they pose special challenges due to the
  fact that there are numerous technologies
  involves
• web-based application components must be
  thoroughly tested to ensure that they are
  reliable, defect-free, and meets its original
  design purposes

51
Web ApplicationsClient-side Components
NetObjects Support
ü
ü
ü
52
Web ApplicationsServer-side Components
Firewall
û
Application Server
Mainframe Database

• Prevents unauthorised access to Intranet
• Implements security policy and stance for
  Web Applications

Database Server

• provides special purpose applications
  necessary to support a web application
• generally invoked by passing a request from a
  CGI script

• Central repository for
• all data in the organisation
• Database Server provides a view on the
  necessary subsets of this central repository
  data

• provides database access for a web
  application
• implemented using SQL commands
• must support the database needs of a large
  number of potential users

Web Server

• Production
• Serves HTML/XML web pages
• runs CGI scripts to provide added functions to
  web applications
• Development
• handles an internal representation of pages
  in a web application

û
ü
û
û
û
NetObjects Support
53
Web ApplicationsVarious Kinds of Testing

• Client-side Testing
• Browser compatibility testing
• Desktop configuration testing
• Usability testing
• Documentation testing
• Security testing
• Error message testing
• Client load testing
• Cross-platform portability
• Applet/Script Testing
• GUI Testing

• Server-side Testing
• Web-server Load testing
• Network Load Testing
• Application Server Testing
• Database Server Load Testing

54
Dynamic Websites
55
Dynamic Websites

• we have seen that organisational multimedia
  systems can be considered in the same way as
  other organisational web applications
• multimedia content may be distributed across
  multiple servers-and served as required
• there is still a major problem that faces
  conventional multimedia developers- although the
  content is now in principle able to be changed-
  this is difficult to undertake and so the
  multimedia site may suffer from the so called
  revision control problem also known as version
  control problems

56
Static Site StructureFile System View
57
Static Site StructureChanging Contents- Revision
Control Issue
58
Static Site StructureChanging Contents- Revision
Control Issue
59
Static Site StructureChanging Contents- Revision
Control Issue
60
Static Site StructureChanging Contents- Revision
Control Issue

• Clicking on Adityas member link not only
  provides the content but a previous version of
  DSL websites navigation frame
• Static site structure easily creates situations
  where revision control errors like this can occur

61
Static Site StructureChanging Contents- Revision
Control Issue

• Clicking on Rodneys member link provides content
  that is well-out-date
• Static site structure easily creates situations
  where revision control errors like this can occur

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Static Site StructureChanging Contents- Revision
Control Issue
N
63
Static Site StructureLongitudinal Changes
N
64
Static Site StructureLongitudinal Changes
N
65
Static Site StructureLongitudinal Changes
Time
Content Theme
N
66
Static Site StructureLongitudinal Change
Content Themes

• different content themes (found as major global
  navigation options) are pictorially represented
  by the use of different coloured shapes along
  the x-axis
• we can show changes to the site content over time
  (also called longitudinal change) along the
  y-axis
• most web sites start out with well defined
  content t0

Time
t0
Content Theme
67
Static Site StructureLongitudinal Changes

• the site remains unaltered until the content is
  deemed to have a large number of errors in it
• a review process is instigated and a new version
  for some of the content is created (t1)
• the next increments see the content changing in
  terms of its thematic classification (changes to
  colour) and its representation on the site
  (thickness)

Time
t1
Content Theme
68
Static Site StructureLongitudinal Changes

• while all of the site will need to be reviewed
  not all of the content needs to be or can be
  changed (see boxed themes) t2
• sometimes the changes needing to be made
  represent an enormous burden as the site may need
  to be altered substantially t3
• this episodic, large scale updating websites is a
  major maintenance problem

t3
Time
t2
t1
Content Theme
69
Static Site StructureLongitudinal Changes

• while all of the site will need to be reviewed
  not all of the content needs to be or can be
  changed (see boxed themes) t2
• sometimes the changes needing to be made
  represent an enormous burden as the site may need
  to be altered substantially t3
• this episodic, large scale updating websites is a
  major maintenance problem

t3
Time
t2
t1
Content Theme
70
Static Site StructureLongitudinal Changes

• while all of the site will need to be reviewed
  not all of the content needs to be or can be
  changed (see boxed themes) t2
• sometimes the changes needing to be made
  represent an enormous burden as the site may need
  to be altered substantially t3
• this episodic, large scale updating of websites
  is a major maintenance problem

t3
Time
t2
t1
Content Theme
71
Dynamic Website Dynamic Web Page Generation

• dynamic web applications are prevalent in
  commercial (e-commerce) sites, where the content
  displayed is generated from information accessed
  in a database or other external source
• a dynamic web page is a page that interacts with
  the user, so that each user visiting the page
  sees customized information
• both a web page's structure as well as its
  content can be customized- dynamic web page
  programming can produce web pages on-demand

72
Dynamic Website No Material Presence

• generally dynamic page generation is limited to
  specific small parts of the web
• but there is a more radical alternative to having
  static or scalable web sites- one which has a
  great deal of promise commercially and in
  organisational multimedia systems
• we can extend the idea of dynamic web pages to
  that of having dynamic web sites- sites that do
  not have a material presence until requested as
  part of the user navigation clicking on links

73
Dynamic WebsitesDescription and Rationale

• develop dynamic site structure- sites that appear
  to the users to be dynamically change their
  structure to accommodate use
• in fact when the user is navigating they are
  actually sending database queries and the web
  server generates the page on the fly
• needed for organisations that are involved in
  time or priority ordering in tasks (event
  management or emergency services)
• active area of research
• modify systems network notation to include
  temporal logical
• develop a semantic theory of site evolution (has
  been done for traditional IS)

74
Dynamic Websites

• the structure of the web site changes overtime,
  topics diverge and converge
• weblets blur one into another overtime, as
  indicated by the gradual changes in colour
• this change is driven by changes to types of
  requests being made over time- changes to the
  mission of the organisation and/or structural
  alterations to the communities that make up the
  organisation

Time
Content Theme
75
Further Reading

• Liu, C. Peek, J. Jones, R. Buus, B. and A. Nye
  (1994) Managing Internet Information Services
  Chapter 18 Setting Up a Web Server, OReilly
  Associates, Inc. 299-324
• Liu, C. Peek, J. Jones, R. Buus, B. and A. Nye
  (1994) Managing Internet Information Services
  Chapter 20 Web Gateways and Forms, OReilly
  Associates, Inc. 357-380
• Liu, C. Peek, J. Jones, R. Buus, B. and A. Nye
  (1994) Managing Internet Information Services
  Chapter 21 Web Access Control and Security,
  OReilly Associates, Inc. 381-390
• Berghel, H. (1996) HTML Compliance and the
  Return of the Test Pattern Communications of the
  ACM February 39 (2) 19-22 (Reading 22)

76

• Luotonen, A. (1998) Web Proxy Servers Prentice
  Hall PTR Web Infrastructure Series NJ Prentice
  Hall PTR
• Fournier, R. (1999) A Methodology for
  Client/Server and Web Application Development
  Yourdon Press Computing Series, NJ Yourdon
  Press, Prentice Hall
• Lodin, S. W. and C. L. Schuba (1998) Firewalls
  fend off invasions from the Net IEEE Spectrum
  February 1998, 35 (2), 26- 34 (Reading 24)
• Oppliger, R. (1997) Internet Security Firewalls
  and Beyond Communications of the ACM May 40 (5)
  92-102 (Reading 25)
• Wood, D. (1998) The Search for the Searcher Use
  second-rate search engine software and your users
  will avoid your Web site in droves Systems April
  1998, 58-67 (Reading 26)

77

• Anonymous (1998) Serving from the baseline APC
  Labs checks out entry-level Web servers from
  small-to-medium businesses APC Magazine April
  1998, 115-124 (Reading 27)
• Schwartz, R. L. (1999) Programming with Perl
  Step-by Step Link Verification Web Techniques 4
  (3) March 1999, 30-34
• Yeager, N. J. R. E. McGrath (1996) Web Server
  Technology The Advanced Guide for World Wide Web
  Information Providers San Francisco, California
  Morgan Kaufmann
• Holden, G. and M. Keller (1999) Apache Server for
  Windows Little Black Book Arizona Coriolis

78
Links

• Web Techniques www.webtechniques.co
• NewApps Software Archive http//www.newapps.com/ap
  pstopics/Win_95_HTML_and_Link_Verification_Tools.
  html
• Viable Software Alternatives- Alert LinkRunner
  http//viablesoftware.com/
• Tetranet Software- LinkBot Pro http//www.tetranet
  software.com/products/linkbot.htm
• Trellian- SiteMapper http//www.trellian.com/mappe
  r/
• Aman Software- CyberSpyder Link Test 2.1.5
  http//www.cyberspyder.com/cslnkts1.html
• Hausherr, Tilman- Xenu's Link Sleuth
  http//www.snafu.de/tilman/xenulink.html
• comp.lang.tcl Frequently Asked Questions (1998)
• http//www.cis.ohio-state.edu/hypertext/faq/usenet
  /tcl-faq/part1/faq-doc-2.html

79

• Bourne Shell (1994)
• http//garfield.ir.ucf.edu/manual/aix/bourne.html
• CGI Programming 101 (1997-1998)
• http//lightsphere.com/dev/class/
• Comprehensive Perl Archive Network (1998)
• http//ftp.digital.com/pub/plan/perl/CPAN/CPAN.htm
  l
• IPSec Online (1998)
• http//www.data.com/tutorials/bullet_online.html