Cocomo II Maintenance

1
Cocomo IIMaintenance ReuseEEE493
2001ReferencesHvV 7.3.6
Royal Military College of Canada Electrical and
Computer Engineering
Major Ron Smith smith-r_at_rmc.ca 1-613-541-6000
ext. 6030

• Major Greg Phillips
• greg.phillips_at_rmc.ca
• 1-613-541-6000 ext. 6190

2
COCOMO II -Maintenance Model Assumptions

• essentially, the same set of cost drivers apply
  to software maintenance as for development
• maintenance includes
• redesign and recoding of small portions of an
  original product,
• redesign and development of interfaces, and
• minor changes to structure
• maintenance is either
• an updates or
• a repair (corrective, adaptive or perfective)

3
COCOMO II -Maintenance Model Considerations

• Required development schedule (SCED) and required
  reusability (RUSE) cost drivers are not included
  in the maintenance model
• Required software reliability (RELY) has an
  inverse effect as a cost multiplier
• ie, if the product was developed with a low
  reliability requirement, it will be more costly
  to fix latent defects

4
Maintenance Model (1)

• apply scale factors to the size of the modified
  code as opposed to the size of the product being
  modified (COCOMO.81)
• effort, PMM a x SizeM b x ? EMi (i 1 to
  15)
• staffing level, FSPM PMM / TM
• where
• SizeM - changed KSLOC (added and modified)
• TM - desired maintenance activity duration

5
Maintenance Model (2)

• determining code size includes factors for
  software understanding and programmer
  unfamiliarity
• code size, SizeM Base Code Size x MCF x MAF
• with MCF (Size Added Size Modified)/ BCS
• MAF 1 (SU/100) x UNFM
• where
• size added/modified may be in KSLOC, UFPs or
  APs
• BCS - base code size (original code)
• SU - software understanding increment (10 - 50)
• UNFM - programmer unfamiliarity (0.0 - 1.0)

6
COCOMO II -Reuse Model Assumptions

• in order to factor in the costs /efforts of
  software reuse, an estimate is established for
  the extent that reused code will require
  modification / adaptation
• determining this effort must also include
  considerations for the degree of assessment and
  assimilation required to integrate existing code
  into new product
• how much effort will be required to find and/or
  assess the applicability of any reuse components
• a size equivalent is determined for reuse, which
  is then added to development code size

7
COCOMO II -Reuse Model Considerations

• as with COCOMO.81, an adaptation adjustment
  factor is determined by considering the extent of
  required redesign, recoding and re-integration
• default efforts for each phase are assumed to be
  40, 30 and 30 respectively
• adjustment factor AAF 0.4 DM 0.3 CM 0.3
  IM
• where
• DM - adapted softwares design is modified
• CM - adapted softwares code is modified
• IM - of effort required to integrate adapted
• software into product as compared to software
  of
• equivalent size

8
Reuse Model (1)

• reuse equivalent code size is determined based
  upon adjustment factors for size of modified
  code, assimilation, understanding and
  unfamiliarity
• reuse size, SizeRU SizeA AA AAF (SU x
  UNFM) /100
• where
• SizeA - size of the original adapted code
• AA - of assessment and assimilation
• AAF - adaptation adjustment factor (previous
  slide)
• SU - software understanding increment (10 -
  50)
• UNFM - programmer unfamiliarity (0.0 - 1.0)

9
Reuse Software Guidelines
10
Assesment and Assimilation Increment
in percentage ()
11
Software Understanding Increment
12
Programmer Unfamiliarity Factor
13
Supplemental References

• Boehm, Barry, et al., Software Cost Estimation
  with COCOMO II , Prentice-Hall, 2000. ISBN
  0-13-026692-2.

14
Next ClassCOCOMO II - A Worked Example