1. Chapter 14: Maintenance Effort Models Omar Meqdadi SE 3860 Lecture 14 Department of Computer Science and Software Engineering University of Wisconsin-Platteville

2. 2 Topic Covered Maintenance Effort Factors Maintenance Effort Models

3. Application type and maintainability System novelty Maintenance staff skills System life span ( system age ) Dependence on a changing environment Hardware characteristics System Quality:  Design quality  Code quality  Documentation quality  Testing quality Factors Affecting Maintenance Effort

4. 4 Factors Affecting Maintainability of an Application Application Size (KLOC) Application Age Programming Language 4gls produce more maintainable code than 3gls Design Methodologies  well designed software is much easier to maintain Program Structure  Good program structure means easier to maintain Processing Environment  real-time systems harder than batch systems

5. 5 Factors Affecting Maintainability of an Application Modularization  High cohesion and low coupling Documentation generation  Maintenance of documentation is as expensive as maintenance of code End-user involvement  when end users are more involved then maintenance decreases  Example: XP development approach Maintenance management  management affects productivity

6. Problems in Managing Maintenance Changing priorities Inadequate testing methods Performance measurement difficulties System documentation incomplete or non-existent Adapting to the rapidly changing business environment

7. 7 Maintenance Problems Ranking 1. Changing priorities 2. Testing methods 3. Performance measurement 4. Non-existent system documentation 5. Changing business requirements 6. Measurement of contributions 7. Lack of personnel, especially experienced 8. Lack of maintenance methodology, standards, procedures and tools

8. 8 Maintenance Effort Models Belady and Lehman COnstructive COst MOdel (COCOMO)

9. 9 Effort Model1: Belady and Lehman Model of maintenance effort M = p + K^(c-d) Where:  M = total maintenance effort over entire lifecycle  p = productive efforts: analysis, design, code, test  c = complexity due to lack of structured design and documentation  d = degree of familiarization with the system  K = empirically determined constant

10. 10 Effort Model1: Belady and Lehman From this model:  Cost of maintenance increases exponentially  Costs are reduced by structured development  Costs are reduced by giving the maintenance team time to become thoroughly familiar with the system

11. 11 Effort Model2: COCOMO Model of maintenance effort Effort = ASLOC* (AA + SU + 0.4*DM + 0.3*CM + 0.3*IM)/100 Where:  ASLOC: number of source lines of code to be adapted  AA: assessment and assimilation effort  SU: amount of required software understanding  DM: percentage of design to be modified  CM: percentage of code to be modified  IM: percentage of external code to be integrated

12. 12 Effort Model2: COCOMO Rating for SU Very lowLowNominalHighVery high StructureVery low cohesion, high coupling, spaghetti code Moderately low cohesion, high coupling Reasonably well structured, some weak area High cohesion, low coupling Strong modularity, information hiding in data and control structure Application clarity No match between program and application worldviews Some correlation between program and application Moderate correlation between program and application Good correlation between program and application Clear match between program and application worldviews Self descriptiveness Unclear code; unclear or missing documentation Some code commentary headers; some useful documentatio n Moderate level of code commentary headers, and documentation Good code commentary and headers; useful documentation ; some weak areas Self descriptive code; documentation up-to-date, well organized, with design rationale SU increment5040302010

13. 13 Effort Model2: COCOMO Rating for AA Effort Assessment and Assimilation Increment Level of Assessment and Assimilation Effort 0None 2Basic component search and documentation 4Some component test and evaluation documentation 6Considerable component test and evaluation documentation 8Extensive component test and evaluation documentation