Software Project Management

1
Software Project Management

• Resource availability and critical chain
• INFO 638
• Glenn Booker

2
Resource Availability

• To make a project schedule complete, resources
  need to be assigned to each task
• Need to identify the number of resources, and
  their roles
• 3 senior programmers
• 0.1 program manager
• 1 database analyst, etc.

3
Resource Availability

• Now we need to determine if the project can be
  completed with the resources available
• The key is to balance the resources with the
  tasks they need to accomplish some refinement
  of the tasks and activities in the project is
  often needed

4
Leveling Resources

• Resource assignments are generally done
  task-by-task at first
• Then need to add up the planned resources and
  look for potential problems
• Over committing people
• Resources inconsistent with project priorities

5
Leveling Resources

• Lack of management to monitor the project
  resources
• Lack of accounting for employee turnover
• Leveling should result in no resource being
  planned to work more than 100 of the time
• And we want a logical flow of resources needed
  no wild fluctuations

6
Leveling Resources

• No schedule is typically perfect we want to get
  reasonably close however
• Strategies to level resources include
• Use available schedule slack
• Shift the project finish date
• Smoothing

7
Use available schedule slack

• Slack is the amount of time a tasks start or
  completion could be changed without affecting
  project completion
• Hence we can slide tasks left right on the
  schedule within the limits of their slack time to
  smooth out resource needs

8
Shift the project finish date

• If the completion date isnt critical, consider
  moving it to the right (later) in order to avoid
  resource conflicts (multiple tasks needing the
  same resource at once)
• Otherwise might need to reduce the project scope
  to eliminate conflicting tasks, or defer feature
  completion to later releases

9
Smoothing

• Here, smoothing refers to deliberately planning
  people to work overtime to accomplish certain
  tasks
• Done by scheduling gt8 hours of work per day, or
  using weekends and/or holidays as work days

10
More Approaches

• Other ways to help smooth the resource needs
  include
• Decompose activities into smaller tasks, and
  spread out when those tasks are done
• Stretch the duration of tasks, thereby reducing
  the number of resources needed
• Use less skilled resources, and extend the
  schedule for the task accordingly

11
Cost of Resource Leveling

• Often leveling or smoothing resources can lead to
  a longer project schedule
• This may increase the cost of the project,
  particularly if fixed project costs are affected
  (e.g. facility rent)
• More direct costs could include failure to earn
  early completion incentives, or penalties for
  late project completion

12
Micro-level Planning

• Its possible to plan subtasks to a very fine
  amount of detail (day or two subtask task
  durations)
• This can be a good strategy for understanding
  serious estimation problems
• In general, however, the added cost of planning
  and tracking isnt worth it

13
Work Packages

• Earlier we defined a project as having
  activities, which are broken into tasks
• A way to describe and manage the tasks within an
  activity are work packages
• The work package describes the tasks to be
  accomplished, relevant dates, and who will do the
  work

14
Work Packages

• Sometimes a work package is also a contractual
  mechanism to describe a chunk of work to be
  accomplished
• The manager of a work package is responsible for
  managing the tasks needed to get the work done,
  and report the time and effort needed, and the
  work packages status

15
Work Packages Insurance

• The work package can also be seen as insurance to
  describe the work in enough detail to help
  recover if turnover is a problem
• During the peak of the dot-com boom, this would
  have been a very wise strategy to follow

16
Work package assignment (p. 155)
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Work Packages

• The list of all work packages are summarized,
  like shown on the previous slide
• Then each work package (A, B, etc.) is described
  in task-level detail using the form on page 156
  of the text
• Notice that several fields in the top of the form
  come from the main schedule predecessors,
  successors, critical path, etc.

18
WP Implications on schedule

• Whether you use work packages has strong
  implications on the level of detail that appears
  in your master schedule
• If using work packages, you could plan to the
  activity level, and leave the details of each
  activity to the work package managers to define
• If not using work packages, the main schedule
  needs to plan to the task level

19
Complete Project Plan

• With the project defined to the task level you
  have enough detail to estimate the labor costs,
  and are able to provide a complete project
  proposal to upper management for approval to
  proceed

20
Critical Chain Project Management

• Critical Chain Project Management (CCPM) is
  another approach to managing resource conflicts
• Key additional reference is Critical Chain
  Project Management by L. Leach, ISBN 1580539033

21
Critical chain vs. critical path

• The critical path is the longest duration through
  the project
• Doesnt consider the resources needed for tasks
  along the critical path
• Critical chain is the longest path through the
  project, considering both task dependencies and
  resource constraints

22
How is CCPM different?

• CCPM is based partly on some statistical concepts
• The duration of any task will vary, depending on
  various reasons
• Those reasons could be due to common causes
  (normal random fluctuations) or special causes
  (specific causes which could be identified)

23
Common Special Causes

• Common causes are accounted for in the
  contingency planning for each task the amount
  of time needed to ensure its completed on time
• Special causes are dealt with as part of risk
  management

24
Plan for 50 Completion Time

• Normally we plan each task so that 90 of the
  time wed finish on time
• This includes a lot of time for each task
  compared to the 50 completion time (the task
  time wed finish in 50 of the time)
• CCPM plans for the 50 completion time, and adds
  the additional time as contingency time

25
Figure 12.1, page 254

• This is what the cited figure means the white
  part of each task is the time needed to finish it
  50 of the time
• The grey part is the difference between 90 and
  50 completion times
• In CCPM we lump the 50 times together, and lump
  the grey parts into a contingency time period

26
Notice the assumption

• The text assumes that the difference between 90
  and 50 completion times is very large
  typically half of the planned duration
• So tasks with a 90 duration of 6 days, have a
  50 duration of 3 days
• Is this realistic?

27
To create a critical chain path

• Start with the early schedule from traditional
  project management (TPM) figure 12.2, the
  critical path is tasks C1-C2-C3
• Replace the 90 completion times with 50
  completion times for every task

28
To create a critical chain path

• Convert the early schedule to the late schedule,
  and show resources the late schedule is shown in
  Fig 12.3
• Look for resource conflicts, and adjust the start
  time for each task(here its assumed each person
  can work one task at a time)
• Add time buffers

29
Time Buffers

• Buffers are time intervals added to the end of a
  series of tasks to allow for contingencies
• Buffers can be used for many reasons
• Project buffers
• Feeding buffers
• Resource buffers

30
Project buffers

• Project buffers are at the end of a critical
  chain, to protect the overall project schedule
  (allow for general contingencies)
• If T50i is the 50 completion time for task i on
  the critical chain, T90i is the 90 completion
  time for task i, then project buffer sqrt S
  (T90i T50i)2

i
31
Feeding buffers

• A feeding buffer is a buffer at the end of a
  series of tasks which feed into the critical
  chain (like a stream which feeds a river)
• It is calculated the same as a project buffer

32
Resource buffers

• A resource buffer isnt a time buffer at all
  its a flag to warn that a particular resource
  will be needed soon
• So its an alarm clock!
• A resource buffer is established some time
  interval before the resource is needed (1 week, a
  month, etc.)

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Return to CCPM example

• Resume the example from slide 28
• Add feeding buffers onto the end of tasks A1-A2
  and B1-B2 (since they feed the critical chain C)
• Add project buffer onto the end of tasks C1-C2-C3
  (since it is the critical chain)
• Notice that resource conflicts arent considered
  for buffer time periods

34
Return to CCPM example

• The project which was 16 days originally (under
  TPM) is 13.7 days using CCPM
• A schedule reduction of 14

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Managing a project using CCPM

• Since the nominal task duration is only met 50
  of the time, there have to be careful rules for
  managing the buffers
• Three levels of warning are established
• When the first, second, and final thirds of the
  buffer are entered
• None for when the buffer is exceeded?

36
Managing a project using CCPM

• How seriously each of these warnings is treated
  depends on how far into the series of tasks you
  are when the buffer is used
• Again using a scale of first, second, and final
  third of the tasks accomplished
• This produces the chart on page 261

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Managing a project using CCPM

• So if a series of tasks is 15 days long, and has
  a 10 day buffer
• If you are 8 days into the buffer after
  completing 7 days of the tasks work
• The tasks are 7/15 into the work, which is the
  second third of the tasks
• The buffer used is 8/10, which is the final third
  of the buffer
• Hence the diagnosis is Serious problem
  implement the solution

38
CCPM Summary

• So CCPM uses a little statistics, and a little
  risk management theory to reduce the planned
  schedule for completing a project
• Several examples of success using CCPM are cited