COMM1T Web Engineering

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COMM1T Web Engineering

• Week 9 - Web Server Installation. Website
  Configuration Management

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What is aweb server?

• A network server manages access to files, folders
  and resources.
• A web server manages this access across the
  internet or local intranet.
• Web servers use platform-independent HTTP
  (HyperText Transfer Protocol).
• Web servers also perform the following
• handle permissions.
• execute programs (e.g. CGI Scripts).
• keep track of directories files.
• communicate with client computers.

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How does a web server work?
Web Server
Run Server program
The returned file may be an HTML file, image,
Java applet etc.
HTTP Response return file
HTTP Request
Browser
Client Computer
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Common Web Servers

• Microsoft Personal Web Server (PWS)
• Entry level web server.
• Doesn't support FTP (file transfer protocol).
• Microsoft Internet Information Server (IIS)
• Popular web server for Windows NT.
• Apache
• Popular web server for UNIX NT.
• High performance/reliability.
• W3C Jigsaw
• Blueprint for the future!

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Personal WebServer

• A free web server which can be downloaded.
• Produced by Microsoft
• Can be installed with the following operating
  systems
• Windows 95
• Windows 98
• Windows NT
• Download from
• http//www.microsoft.com/msdownload/ntoptionpack/a
  skwiz.asp
• Product home page
• http//www.microsoft.com/windows/ie/pws

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Internet Information Services (IIS)

• Internet Information Services (IIS) is the most
  popular web server for Windows NT.
• IIS is an integrated feature of Windows 2000/XP.
• Download from
• http//www.microsoft.com/ntserver/nts/downloads/re
  commended/NT4OptPk/
• Product home page
• http//www.microsoft.com/ntserver/Basics/WebServic
  es/

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Web ServerStructure

• A web server has a physical directory structure
  on disk.
• This maps onto a virtual directory structure for
  internet access.
• Management depends on web server used.
• If for example the homepage was stored in
• ...\users\cs0egandy\public_html
• This directory might be accessed from the web
  using
• http//osiris.sunderland.ac.uk/cs0ega/

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Demonstration

• http//osiris.sunderland.ac.uk/cs0ega/

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Virtual directories

• Multiple websites on the same web server are
  placed in separate virtual directories.
• To add a new website, a new directory will be
  created and the website file structure placed
  under it.
• An alias for the virtual directory will be mapped
  to the physical directory on disk.
• This alias is the name by which the directory is
  referred to from the internet.

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Example

• A virtual directory has been created with alias
  webeng.
• This is mapped to the physical directory
• ...\users\cs0webeng\public_html\
• Files placed in this directory will now be
  accessible from
• http//osiris.sunderland.ac.uk/webeng/
• An index.htm file has been provided and this will
  provide the starting point for the website.

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Demonstration

• http//osiris.sunderland.ac.uk/webeng/

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Sub-directories

• The same principle works for directories under a
  website structure.
• A developer can create a new directory under
  their root web directory e.g.
• ...\users\cs0webeng\public_html\testdir\
• If they place a default file index.htm (or other
  valid default name) this can be accessed
• http//osiris.sunderland.ac.uk/webeng/testdir/
• In this case no web server alias is required.

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Demonstration

• http//osiris.sunderland.ac.uk/webeng/testdir/

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Directory Listings

• What happens if no default file is provided?
• Within the website another sub-directory has been
  created
• ...\users\cs0webeng\public_html\programming\
• This directory does not contain a default file so
  an initial page cannot be identified
• A directory listing is displayed instead.
• For this to work the web server must be
  configured to enable "Directory Browsing.
  Usually a simple option, available when creating
  website accounts.

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Demonstration

• http//osiris.sunderland.ac.uk/webeng/programming/

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Web Servers andCGI Programs

• Web Servers also provide a virtual directory with
  alias scripts to enable execution of CGI
  programs.
• This is mapped to physical directory
• ...\users\cs0webeng\public_html\scripts\
• CGI programs should be copied into this
  directory.
• They can then be accessed through
• http//osiris.sunderland.ac.uk/webeng/scripts/
• Note that execute scripts permissions are set
  for this directory by the Web Server Manager if
  scripting is allowed.

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Demonstration

• http//osiris.../webeng/scripts/randback.exe

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File Transfer

• So far we have simply copied files to directories
  on the server.
• This is fine when you have access to the web
  server via a network.
• With larger servers (such as those run by ISPs)
  the users are widely distributed.
• A network connection may not be possible.
• In this case files are copied to/from the server
  using FTP (File Transfer Protocol).
• FTP copies both binary and ASCII (Text) files.

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FTP Software

• There are many FTP programs (most are free
  downloads)
• Examples are
• WS-FTP
• LeechFTP
• WinSCP
• At Sunderland WinSCP is widely used and
  recommended
• http//winscp.sourceforge.net/eng/)

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Demonstration

• WinSCP

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WebsiteManagement Issues

• Why bother managing a website?
• Why shouldn't the website be left to evolve
  naturally?
• Surely new pages can be added as necessary?
• Out of date hyperlinks? Surely a regular check is
  sufficient.

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Reasons for management

• Web engineering is a complicated technical
  activity.
• Additional non-technical tasks are required.
• Often large teams are involved.
• Development costs can be high.
• To avoid failure
• Plan the project/website.
• Consider the risks.
• Establish a schedule.
• Track progress.
• Ensure appropriate controls are in place (quality
  assurance).

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Web Engineering skills

• Software engineering, component-based.
• Networking.
• Architectural design.
• Navigational design.
• Internet standards/languages.
• Security.
• HCI (Human Computer Interface) design.
• Graphic design.
• Content layout.
• Application testing.

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A Web Engineering Team

• Content developer provider.
• Generation and/or collection of content from a
  range of sources.
• Web publisher.
• Organise content and act as liaison between
  content developer and web engineer.
• Web engineer.
• Cuts code!
• Support/maintenance specialist.
• Responsible for corrections, adaptations
  enhancements.
• Administrator.
• Responsible for day-to-day operation. The
  "webmaster".

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Configuration Management

• Software Engineering SCM (Software Configuration
  Management) principles can be applied.
• Web applications are frequently changing.
• Often many developers are working on a single
  website.
• inadequate control may result in
• unauthorised posting of information.
• simultaneous posting of information (updates may
  be lost).
• erroneous or poorly tested functionality.
• security may be breached.

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SCM Issues

• Content
• Requires organisation and formal methods of
  control. Who updates what and when?
• People
• Often web pages are created/updated by people
  without a software engineering background.
• They may be unaware of need for configuration
  management.
• Website can grow/change in an uncontrolled way.
• Scalability
• Websites commonly start small and expand.
• Small changes can have large effects.
• Politics
• Who "owns" the website?
• Who pays for changes/corrections?

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SCM Processes

• Version control.
• Change control.
• Configuration audit.
• Status Reporting.
• Tools available for general software
  configuration control can be used in web
  engineering.
• Examples of such software
• Microsoft Visual SourceSafe (included with Visual
  Studio Professional).
• SCCS (Unix).

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Version Control
v1.3
v1.4
v1.0
v1.1
v1.2
v2.0
v2.1
v1.1.1
v1.1.2
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ChangeControl
User requests change
Developer evaluates
Change report generated
Change control authority decides
Request is queued for action
Change request is denied
Developer is assigned
User is informed
Items required are "checked out"
Change is made
Change is reviewed/audited
Local testing is performed
Items are "checked in"
Changes set for inclusion in next release
All changes to version reviewed/audited
Release/Distribute new version
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Access Control
Check in
Modified version
Baseline version
unlock
audit info
ownership info
Project Database (Source Files)
Access Control
Web Engineer
lock
Baseline version
Extracted version
Check out
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WebsiteArchitecture

• When designing a website you must plan the
  architecture.
• How will the user navigate your website?
• What links are required between pages?
• What external links are required?
• Consider maintenance/expansion.

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Linear Architecture
Linear with optional flow
Linear with diversions
Linear
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Use of Linear Structures

• When a predictable sequence of iterations (with
  some diversion or variation) is expected.
• Examples
• The Exercises section of the WebEng site where
  students are expected to move through in order.
• The ordering section of a website where you move
  through a checkout system.

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Grid Architecture
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Use of Grid Structures

• When the content can be organised into categories
  of one or two dimensions.
• Example
• A site selling equivalent products produced by
  different manufacturers.
• Navigate horizontally to locate the required
  product.
• Navigate vertically to compare different
  manufacturers.

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Hierarchical Architecture
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Use of Hierarchical Structures

• The most common type of website structure.
• Allows navigation horizontally between different
  vertical branches of the structure.
• Allows rapid navigation across content.
• Can be confusing to the user.

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Networked ("Pure Web") Architecture
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Use of Networked Structure

• Every page is linked to every other page.
• Complete flexibility of navigation.
• Considerably confusing to the user.
• What happens if a page is removed?
• A maintenance nightmare!

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Website Navigation

• Structures can be combined to form composite
  structures.
• The overall architecture of a website is
  generally composite.
• The website designer must take into account the
  following
• Good navigation between related pages.
• Do not confuse the user with too many links.
• What form should the links take - text, buttons,
  tabs?
• Maintenance/expansion should be taken into
  account.

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Directory Structures

• Websites can quickly become large and
  complicated.
• The use of a sensible directory structure is
  important.
• It is common to have separate directories for
  images and scripts.
• Other sub-sections should be separated out into
  separate directories.
• Links should be relative not absolute so they are
  not broken if the site moves.

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Testingwebsite links

• Broken hyperlinks are extremely irritating to the
  user.
• Before releasing your website you should check
  all links are valid.
• Tools are often included in Development Software
  e.g. Visual InterDev, Pagemill.
• Links to external sites should be checked
  regularly.
• If you make significant changes to your website,
  check internal links.
• As your website expands, ensure appropriate links
  to new sections (and back) are added.

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References

• Material for this lecture was obtained from
• "Software Engineering a Practitioner's Approach
  (European Adaptation)" Pressman Ince Schaum,
  2000 ISBN 0-07709-677-0
• "Internet World Wide Web How to Program"
  Deitel, Deitel Nieto Prentice Hall ISBN
  0-13-030897-8.
• Example CGI Program was provided by
• Dr. Giles Oatley