Web Evolution: Theory and Practice

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Web Evolution Theory and Practice

• Cornelia Boldyreff
• Distributed Systems Engineering Group,
• RISE, University of Durham, UK
• www.dur.ac.uk/cornelia.boldyreff

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Programme of Lectures

• Background and Introduction to Web Evolution
• Establishing a Measurement Programme for the WWW
• Web Design Processes and Methods from SE to WE
• Specific Web Evolution and Web Engineering
  Research Projects at Durham
• Questions and Answers, Discussions

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Lecture 1 - Outline

• Web Site Development and Maintenance
• Web Metrics
• Web Site Evolution
• Web Management and Design Processes
• Web Site Engineering

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Web Site Development and Maintenance

• Recognition of potential Web maintenance problem
  and very interesting case of software evolution
• Key paper - Measuring Readability and
  Maintainability of Hyperdocuments, Hatzimanikatis
  et al, JSM, 1995
• Possibility of working with Richard West and
  colleagues managing UK government Web sites

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Initial Findings

• Uneven, largely poor, quality of authorship
• badly structured documents
• difficulty in navigating hyperdocuments
• hypertext structures expand exponentially with
  continuous linking of nodes
• lack of tools for managing Web development and
  maintenance

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Further Findings

• hyperdocuments on the WWW are often distributed
  and therefore maintained by several
  authors/maintainers
• maintenance of WWW documents relies on the error
  logs of each server, complaints from users,
  periodic checks by owners
• no general consensus of opinion, or standards, on
  what constitutes a good hyperdocument therefore
  assessment is difficult

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Analyzing and Assessing Hyperdocuments

• Readability Factors
• Maintainability Factors
• Effectiveness Factors - Usability
• Evaluation process in practice
• High level factors related to low level
  measurable factors
• Lessons to be learnt from classical software
  engineering, especially software maintenance

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Key Results

• Analysis and Assessment of Web documents
• Requirements Studies for Web Site Development and
  Management Support
• Workbench developed - see www.dur.ac.uk/cornelia.b
  oldyreff/workbench

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Solving the Broken Link Problem

• Major effort needed to maintain links and ensure
  their currency
• Existing solutions involved non-standard
  implementations, e.g. Hyper-G(Hyperwave)
• Guardian Agent solution implemented using
  standard http and CORBA - employing both eager
  and lazy link update - patented by British Telecom

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BT Requirements for WWW Maintenance

• Link management - if documents are relocated,
  links should be redirected automatically to the
  new document location
• Version control - support re-configuration of
  existing sites with new up-dates
• Support of team working - several authors should
  be able to work on the same documents without
  interfering with each other

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Guardian Agents

• Compatible with WWW
• Provide on-line maintenance
• Work in background - transparent to the user
• Flexible
• Scalable
• Configurable

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Guardian Agents

• Guardian Agents analyze, monitor and record the
  following information
• Outgoing and incoming links
• Who accesses the web page
• Who changes the web page

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Determining Success - Web Quality Metrics

• Apply Goal-Question-Metric
• Metrics derived from Software Metrics, e.g.
  Complexity measures
• Tailored Hypertext Metrics, e.g. tree impurity
• New Web Metrics, e.g. Brays html sincerity
• Both static and dynamic measures required

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Software Evolution - Web Evolution

• Inspired by Lehman classic studies in Software
  Evolution
• Metrics here used to study changes over time
• Aim to understand and predict the web evolution
  process
• Support better, more controlled, web maintenance
  and management

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Web Management and Design Processes

• Early process models developed based on UK
  government web site management practice
• Hypermedia/Web Development methods and models -
  surveyed and classified
• Metrics used here to guide research on process
  models for Web Site Engineering

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Web Site Engineering

• Applying and adapting classical Software
  Engineering models, methods and tools to the
  engineering of web-based applications, e.g. web
  pages, web sites.
• Special case of Distributed System Engineering
• Closely related to Software Engineering but also
  recognizing important differences

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Towards Web Site Engineering

• Well developed models of Web development and
  maintenance processes
• Web Software Quality Determination
• Models and Laws of Web-based Software Evolution
• Support for distributed developers - Computer
  Supported Co-operative Working applied to Web
  Site Engineering

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Key Points

• Web developers and maintainers can learn from
  Software Engineering
• Web metrics can help to evaluate, to describe,
  and to develop new approaches to web engineering
  processes and products
• Software Engineering can provide a foundation for
  Web Engineering
• Web Evolution studies provide guidance