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Title: 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

24
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

62
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
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