Software Project Management

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Software Project Management

• Estimation and scheduling
• INFO 638
• Glenn Booker

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After the WBS

• Once the rough scope of tasks has been defined in
  the WBS, we need to estimate each task in terms
  of duration and effort
• From effort well get the cost of each task, and
  eventually the project
• After estimation, can start to organize the
  project schedule

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Welcome to Estimation!

• This is often the most challenging part of
  project management
• Most dont want to admit what their methods are
  for estimating work its just a WAG (wild
  approximate guess ?)
• Estimation is the basis for creating a plausible
  schedule
• Need to estimate the duration and effort of each
  task

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Duration versus Effort

• Duration, or time for a task, is the amount of
  calendar time needed to accomplish it
• Effort is the number of working hours (or months
  or years) needed for a task or project
• One week of effort is 40 hours, one month of
  effort is about 168 hours
• May have units of staff-months, people-months,
  labor-months or man-months

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Average Staffing

• An easy measure of a project is the average
  number of people working on it equal to the
  effort divided by time
• Ave staffing effort / time
• A project might take 9 months (duration) and
  12,000 hours (effort)
• Ave staffing(12,000 hrs / (168 hrs/mo))/
  9 months 7.9 people

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Why Average Staffing?

• Most software projects require few people in the
  beginning, peak in the middle of the project, and
  taper off later on as testing is completed

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Resource Loading

• Resource Loading is the number of people assigned
  to a task
• Some tasks can be completed sooner if more people
  work on them
• Sweatshops of people sewing shirts will produce
  more if there are more employees
• Other tasks might take longer, if tasks are
  dependent upon each other

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Task Duration Varies

• How long does it take to drive from Philly to
  Baltimore?
• Depends on how fast you drive, what route you
  take, traffic, weather, how much construction
  there is, etc.
• Development tasks will vary in duration from one
  person to another depending on their skill level,
  motivation, outside influences, etc.

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Creating a Good Estimate

• There are six techniques for estimating the
  duration and effort of a task
• Similar activities
• Historical data
• Expert advice
• Delphi technique
• Three-point technique
• Wide-band Delphi technique

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Similar activities

• This just means estimate a task based on similar
  tasks in the past
• If youve developed lots of web pages, you can
  safely estimate how long itll take to develop
  similar pages
• A common rule of thumb is to
• Take the time itd take you to do a task, double
  it, and add 10-20

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Historical data

• If you can find data from similar projects
  developed by your organization, they can form the
  basis for a good estimate
• This assumes the project uses similar technology
  as previous projects
• This is why big new projects want to see
  experience developing similar big projects to
  lend credence to your estimates

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Expert advice

• If you dont know anything about the task, ask
  someone who does!
• Could find experts within your organization,
  outside consultants, vendors, academia, etc.
• Notice the first three estimation methods depend
  on someone having experience doing the task before

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Delphi technique

• The Delphi technique is a formal way to get group
  consensus on a wild guess for the estimate
• Get a group of people together
• Tell them about the project and its tasks
• Get them to all estimate the duration of each task

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Delphi technique

• Tabulate the guesses in a histogram called First
  Pass
• For estimates in the outer quartile (lt25 and
  gt75), ask them for their rationale
• Have everyone guess again, and retabulate the
  results Second Pass
• Have the outer quartile defend their choices again

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Delphi technique

• Make a third set of guesses, and use the average
  value for the tasks estimate
• Though it sounds a bit goofy, this method
  actually works pretty well

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Three-point technique

• The actual duration of a task could vary,
  depending on many factors
• Hence there could be a distribution of possible
  values for the duration
• Based on best judgment, determine the Optimistic,
  Most likely, and Pessimistic values for the
  duration, then use Estimate (O 4M P)/6

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Wide-band Delphi technique

• Combine the three point technique and Delphi to
  get the Wide-band Delphi technique
• In each of the three Passes (sets of guesses),
  have each person estimate the Optimistic, Most
  likely, and Pessimistic values
• Use results from the third Pass and apply the
  three point formula

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Estimation Accuracy

• Keep in mind that early estimates of a project
  could be off by a factor of four either way from
  the final effort (McConnell, Rapid Development),
  so dont treat the estimates as perfectly precise
• Expect that estimation accuracy will improve
  throughout the project

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Estimating Resources

• While resources often refers to people on a
  project, it may refer to
• People
• Facilities
• Equipment
• Money
• Materials

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People Resources

• People on a project are generally identified by
  their skills
• Systems analyst, web developer, programmer,
  system administrator, database admin, etc.
• For each activity or task, determine the skills
  needed to perform it
• Your staff has a known set of skills
• Then match up activities to staff (p. 107)

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Facilities Resources

• Part of planning a project is to consider where
  the people will be working
• Might be able to use existing facilities
• Large or long term projects may require leasing
  new facilities
• Need to decide where to put them
• Beware of communication lag between facilities

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Equipment Resources

• Some kinds of activities may require special
  equipment to perform them
• This isnt the material needed to create the
  product equipment refers to anything needed to
  fabricate or test components of the product
• Automated testing is the most common equipment
  need for software

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Money Resources

• Above and beyond the other resources, money may
  be needed for other expenses
• Service contracts for non-project equipment
• Travel expenses
• Office supplies
• Other overhead expenses not covered directly by
  the project

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Materials Resources

• Material costs include the cost of parts that
  become part of the completed product
• This might include various kinds of servers and
  network equipment, software licensing, printers,
  etc.
• This is often the biggest resource after labor

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Organization Chart

• Since we need to define the types of staff needed
  to perform each task, this feeds into developing
  the organization chart of the project
• The roles needed for performing tasks should all
  appear on the org chart
• Its called a Resource Breakdown Structure in the
  text (p. 108)

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Assigning People to Tasks

• Keep in mind that the number of people assigned
  to a task might be a fraction, or greater than
  one
• Hence the duration and effort could be quite
  different
• A low demand task might be assigned to a tenth of
  a person, so a 20-day duration would only have 2
  days of effort

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Cost Estimation

• Cost is easy to estimate once effort has been
  determined and assigned to specific roles
• For labor cost, just multiply effort by the labor
  rate for that role
• A senior programmer might cost 90/hr, so a
  10-hour task would cost 900

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90/hr 187,200/year?!

• Does that labor rate mean the programmer makes
  187.2k/year?
• No, the labor rate also includes overhead
  expenses
• Taxes, vacation, sick leave, health coverage,
  etc. all contribute to overhead
• Pay for managers is often from overhead
• Depending on the organization, ones salary is
  about 35-50 of the labor rate

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Resource Planning

• Now the real challenge of planning occurs
• Need to take the projects needs for people and
  other resources, and make sure its feasible
• Need to avoid committing a given person for
  multiple tasks at once, or scheduling two
  activities in the same facility on one day

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Resource Planning

• Another key is to do load balancing
• Avoid having gaps in a persons schedule
• If you need Pat to run tests in July and
  September, whats she going to do in August?
• Also want to avoid large spikes in staffing needs
• Implies a lot of people hired only briefly

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Cost Control

• The costs for the project consist of cost for all
  of the resources needed
• To manage cost, need to get weekly reports of
  costs incurred, and compare to the plan
• Variances are the difference between the actual
  and planned costs

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Project Network Diagram

• Now that the tasks and activities have been
  resourced (is that a word?), we can put them in
  order
• Need to determine dependencies among the tasks
• Which are sequential? Parallel?
• Which tasks must finish together? Start together?

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Project Network Diagram

• The goals of the Project Network Diagram are to
  help identify key characteristics of tasks, and
  the project as a whole
• When can each task start, at earliest?
• When can we expect completion of the project?

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Gantt Chart

• Editorial note the text hates Gantt charts (p.
  119) whereas most projects Ive seen rely on
  them
• Take your pick whether to use them or not

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Gantt Chart

• Identify major tasks, based on life cycle model
  and project needs
• Determine size and schedule estimates for each
  major task
• Identify sequential or parallel tasks, ongoing
  activities, and task dependencies

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Gantt Chart

• Identify milestones and work products wherever
  possible (decisions, documents, baselines)
• Assign WBS to tasks
• Determine timeline scales needed

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Timelines

• Timelines for a schedule may follow either a
  calendar schedule, or a relative schedule
• Calendar schedule is broken into absolute time
  intervals based on actual time (e.g. Feb. 2004)
• May use a second or third calendar scale of
  larger intervals (quarters, years)
• Calendar (CY) or fiscal (FY) years may be used

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Timelines

• Relative schedule is measured from the start of
  the project - or some other key event - then uses
  time intervals counted from that event (e.g.
  Month 2 after grant received)

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Gantt Chart

• Label each activity with its WBS and task name,
  followed by a bar to represent its duration on
  the timeline
• Milestones are generally a diamond symbol ?
• Used for key decisions
• Symbol format not critical, as long as its
  clear and consistent

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Gantt Chart
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Network Diagrams

• Historic note early network diagrams (and some
  forms of PERT chart) used the lines between nodes
  to represent tasks
• This is called activity on the arrow (AOA)

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Network Diagrams

• Now we use boxes to represent each task and the
  lines between them imply their relationship
• Here, task 3.2 may start after 3.1 finishes, a
  finish-to-start (FS) dependency (very common)

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Network Diagrams

• The other dependencies are
• When task A finishes, task B may finish (FF)
• When A starts, B may start (SS)
• When A starts, B may finish (SF)

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Other Constraints

• Other constraints may affect the relationship
  between tasks
• Technical constraints, such as the way a task may
  need output from a previous task before they may
  begin
• Management constraints, such as to meet
  competitive pressure, or get things done before a
  major event (holiday, conference, etc.)

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Other Constraints

• Interproject constraints, such as the need for a
  related project to finish their side of an
  interface before yours can be fully tested
• Date constraints, where a specific event guides
  an activity, such as needing a task done no
  earlier than, no later than, or on a specific day

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Lag

• Lag can be used to specify delay between events
• Customer surveys are distributed 30 days after
  product release thats a 30 day lag in the
  distribution task
• Lag can be positive or negative

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Creating the Schedule

• These concepts allow the schedule to be created
• For every task, determine its relationship to
  some other task, and lag (if any)
• The early schedule gives the earliest times each
  task may start and finish
• This defines the earliest start (ES) and earliest
  finish (EF) date for each task

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Creating the Schedule

• Conversely, the late schedule gives the latest
  start and finish times without changing the
  completion date
• This defines the latest start (LS) and latest
  finish (LF) date for each task

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Critical Path

• A key output is the critical path, which can be
  defined as
• The longest duration path in the network diagram,
  or
• The series of tasks whose early and late
  schedules are the same dates, or
• The set of activities with zero slack

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Slack?

• Slack (or float) is the amount of delay in
  starting or completing a task that can be
  tolerated without affecting some other task
• Specifically, free slack is the time a task can
  finish without affecting the early schedule of
  anything after it
• Total slack is how much completion of a task can
  be delayed without affecting the project
  completion date

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Detailed Task Estimate

• If we define not just the time Estimate (E) of
  each task, but also compute the earliest start
  and finish (ES, EF) and latest start and finish
  (LS, LF) and slack time, task name ID looks like

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Editorial Comment

• Most projects are doing well to come up with a
  plausible estimate (E) for each task they
  arent going to determine ES, EF, LS, LF, and
  slack time for every task too!!

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Schedule Compression

• Often you need to shrink the projected completion
  date
• Look for tasks which can be done simultaneously
  instead of sequentially
• Look for tasks which may begin when part of a
  previous task is done (instead of all of that
  task)
• Focus on critical path and near-critical path
  tasks

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Schedule Compression

• Look for tasks that can be assigned to more than
  one person (partitionable)
• Look for possible changes to task dependencies
  (beware of added risk)
• SF to SS, for example

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Management Reserve

• At the project level, try to keep a little
  reserve of time (padding) to allow for likely
  schedule slips
• Dont do this on individual tasks tends to
  bloat the schedule
• 5-10 is a good schedule reserve
• So a 6-month project might try to finish 6-13
  work days early
• 6 months 26 weeks 130 work days