Product Metrics An overview

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					Product Metrics
An overview
What are metrics?

“ A quantitative measure of the degree to
  which a system, component, or process
  possesses a given attribute.” [IEE93]

•   Attributes of metrics - Simple,
    persuasive, consistent, Independent and
Software Measures
• Processes are collection of software related activities

• Products are any artifacts, deliverables or documents
  that result from a process activity.

• Within each measure we identify two types of attributes
   – Internal Attributes are those that can be measured in terms of
     the entity itself.

   – External Attributes are those that can be measured only with
     respect to how the product relates to its environment.
Types of Metrics
    • Metrics for Analysis
          • System Size
          • Functionality Delivered
          • Specification Quality
    • Metrics for the Design
          • Architectural Metrics
          • Component Level
          • Interface Design
    • Metrics for the Code
          • Halstead Metrics
          • Complexity Metrics
          • Length Metrics
    • Metrics for Testing
          • Defect metrics
Analysis Model Metrics
   • Function – Based Metrics
     – Function point metric
        • Variables
        • Formula
        • Questions

   • Metrics for Specification Quality
     – Specificity
     – Completeness
Design Model Metrics

    •   Architectural Design Metrics
    •   Object – Oriented Design Metrics
    •   Component – Level Design Metrics
    •   User Interface Design Metrics
Architectural Metrics
 • Focus on characteristics of the architecture with
   emphasis on the structure and effectiveness of modules
   or components within the architecture.
    – Structural Complexity
       • S(i) = [fout(i)] ^2
    – Data complexity
       • D(i) = v(i) / [fout(i) + 1]
    – System complexity
       • C(i) = S(i) + D(i)
       Where fout is defined as the number of modules directly
       invoked by module i. v(i) = number of input and output
       variables in or out of i.
 • Design Structure Quality Index
Object Metrics
    • Size:
        – Population, Volume, Length, Functionality
    •   Complexity
    •   Completeness
    •   Cohesion
    •   Coupling - an indication of “connectedness” of
        a module with others, global data and
    • Volatility
  • System size
    – Number of function calls and objects.
  • Class or method size
    – Size of classes and methods

  • Coupling and inheritance
    – Interdependence of classes. Number and
      complexity of relationships.
  • Class or method internals
    – Complexity and level of documentation

User Interface Metrics
   • Layout
        • Absolute and relative position of entities
        • Frequency of use
        • “Cost of transition”

   • Cohesion
        • Relative connection between on – screen to other on –
          screen content

   • Time
        • Time to achieve an specific action
        • Time to recover from error
        • Time to achieve a use case
Source Code Metrics
    • Lines of code metric
       – Lines of code used to develop a program
       – Set limits on coding lines

    • McCabe’s cyclomatic metrics
       – Path control
       – Logical decision statements and operators

    • Halstead Metrics
       – Depend on the following measures:
           •   Number of direct operators
           •   Number of direct operands
           •   Number of operator occurrences
           •   Number of operand occurrences
       – Predicts
           •   Length
           •   Volume
           •   Time, effort
           •   Number of errors
Testing Metrics
 • Information for testing metrics can be gathered thru
   various sources:
    – Function – based metrics
    – Cyclomatic complexity

 • Halstead Metrics for testing

 • Metrics for OO Testing
    – Metrics used in design provide an indication of design
    – The metrics consider aspects of encapsulation and inheritance
Web Projects

Since web projects can are more dynamic
  than most other types of projects it can be
  harder to measure them.
• Number of static/dynamic pages
• Number of internal page links
• Number of executable functions (scripts,
  applets, etc)

Product Metrics Future

• Application Domain Complexity Research

• Automated Product Metric Tools
  – ESQUT (Evaluation of Software Quality from
    User’s viewpoinT)

• Mathematical Product Metrics
What are process metrics?

  Process metrics really encompasses
    both process and project metrics.
    – Process metrics are used to measure the
      effectiveness of a development process
      over multiple projects
    – Project metrics are used to evaluate
      accomplishment of a single development

Process Metrics

  Process Metrics are generally used at
    the project management level.
    – Strategic in nature
    – Main goal is process improvement
    – Metrics from individuals combined to
      provide group/project metrics
    – Care must be taken to keep individual
      metrics private

Measurement Methods

  Due to the variation in software, and the
    lack of standards, there are many types
    of metrics that can be used
  • Size-Oriented
  • Function-Oriented
  • Object-Oriented
  • Use-Case Oriented


• Metrics are normalized based on the size
  of the software
• Focus on LOC (Lines of Code)
  – Errors Per KLOC (thousand lines of code)
  – Defects per KLOC
  – $ per LOC
  – Page of documentation per KLOC

• Metrics are normalized based on program
• Most commonly used metric is the FP
  (function point)
  – Errors per Function Point
  – Defects per FP
  – $ per FP
  – Pages of documentation per FP
  – FP per person-month


• number of classes reused
• number of classes with defects

Metrics Tools
• SynQuest
• SPQR/20
• SQUID M-Base

Why use Metrics?

"If you can not measure it, you can not
   improve it.“ – Lord Kelvin

•   Characterize - Increase Understanding
•   Evaluate
•   Predict - Managing Software
•   Improve - Guiding Improvements

Why use Metrics - Benefits

Although it can be hard to generate metrics
  from software, there are many benefits
• Manage complexity
• Process improvement
• Quality tracking
• Cost estimation

Why use Metrics - Obstacles

"Not everything that can be counted counts,
  and not everything that counts can be
  counted.“ - Albert Einstein
• Takes time and effort away from the
• Simple project may not benefit
• Projects may vary substantially
• Indicators must be interpreted
Why use Metrics – Bottom
Provides the best option to standardize the
  development process to ensure quality
  and reliability

Establishing a Metrics
  Software Productivity Center, Inc. suggests an 8
      step approach:
  1.   Document the Software Development Process
  2.   State the Goals
  3.   Define Metrics Required to Reach Goals
  4.   Identify Data to Collect
  5.   Define Data Collection Procedures
  6.   Assemble a Metrics Toolset
  7.   Create a Metrics Database
  8.   Define the Feedback Mechanism

Establishing a Metrics
Establishing a program takes planning and
  time to be effective.
• Need historical data from past projects to
  establish indicators
• Goals have to be well defined to be
• Those collecting measures need to be
  vested in the program
• Problems in products in each phase can be detected and
  removed at an early stage by using metrics.

• Metrics provide a quantitative and predictive view of
  potential problems. Thus, they are a powerful tool for
  product development.

• Metrics are still in a young stage. Research is needed to
  set a ground for prediction of problems.

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