Posts Tagged ‘scrum’

Agile Development – RPS Estimation

2009/03/08

Background

Previous article: http://paulecoyote.wordpress.com/2009/02/22/agile-development-vocabulary

This estimation technique based on a simple game of rock, paper, scissors (RPS) is something we have already experimented with to estimate story points for a task.  A story point is a measure of complexity and size of a task (see Agile – Vocabulary), though could be used to estimated time too.

Rock Paper Scissor Estimation… For the win?

Planning Poker

First of all planning poker seems to be way more documented than rock paper scissors estimation, and there are tons of resources about it already on the web.  If planning poker is not familiar to you I would definitely recommend reading up a little about it.  Feel free to also comment if you have come across another discussion on rock paper scissors used in this way for estimation.

In planning poker each player involved in estimation is given cards with a Fibonacci number on representing how many story points a task is worth.  Sometimes decks use a base 2 binary numeral system – something probably more familiar to many software developers.  These are played face down, and on reveal the highest and lowest guessers talk about their estimation with the other players.  Play continues until the values converge.  The strength of rock paper scissors is no props are necessary!

Roshambo!

The rock paper scissors method has roots in the Delphi and Wideband Delphi methods of estimation – but less formal.

Setup

Make sure the people you are playing with have the same idea about what a unit story point is.  It is best if it is a completed simple task you are all familiar with, otherwise you have to start with an agreed duration of time on a task (e.g. half a day).

Nominate one person to marshal the session.  This might be the scrum master (if you are practicing scrum) but the role should switch between team mates.  Rotating the role allows members of the team to grow in confidence talking with their co-workers, encourages joint ownership of the estimation process and it helps the team to jell.

A list of tasks should be given to the marshal to familiarise him or herself with.  The marshal then arranges the meeting.

Scale

Personally I prefer play with the binary numeral system because it is really easy to remember.  You may prefer the Fibonacci numbers which is fine.  Adjust the scale for larger problems or use both hands. Large amounts of story points indicates that the task estimated should be broken down in to more manageable chunks.

  • 0 Fingers:
  • DSC_0264  - 0 fingers Less than 1 story point
  • 1 Finger:
  • DSC_0259 - 1 finger 1 story point
  • 2 Fingers:
  • DSC_0260 - 2 fingers 2 story points
  • 3 Fingers:
  • DSC_0261  - 3 fingers 4 story points
  • 4 Fingers:
  • DSC_0262  - 4 fingers 8 story points
  • 5 Fingers:
  • DSC_0263  - 5 fingers 12 story points
Play
  1. The marshal introduces a task to the group.  Brief further definition of task might be necessary but the marshal should not allow too much detail to be discussed at this point.  It may sway initial estimates, especially if the perceived senior authority on the subject starts talking about complexity and size too deeply.
  2. Marshal counts to three.  At the count of three everyone presents their hands at the same time to the rest of the group.
  3. The person with the largest estimate explains to the group what made them guess the highest.  This helps to draw out unknown facets of the task.
  4. The person with the lowest estimate explains to the group what made them guess the lowest.  This helps to draw out false assumptions, or perhaps something helpful that could simplify working out the task.
  5. Marshal calls for another round of estimations (back to step 2).  Process repeats until the estimates converge.  Estimates should converge, once they do return to step 1 and repeat for each task.

Scale of tasks can be an issue with this form of estimation using the binary numeral system “is Task X really twice as hard as Task Y?”.  Greater scale accuracy can be achieved by using different combinations of fingers.  If using the binary method that could be holding up different combinations of fingers (thumb and index finger could mean “3” for example).  That has it’s own problems because some combinations of fingers are actually pretty hard to carry off for people with less flexible hands.

The strength of this method is that it does not necessarily even need a formal meeting or marshal.  A group of a few people can easily estimate using this method in a corridor, at a desk, etc.

Links

Agile Development – Vocabulary

2009/02/22

Background

This is the start of a series of articles about agile development.  The motivation behind writing these articles is to expand my knowledge of the topic by explaining how I currently understand it.  I imagine feedback from readers about their own experiences and understanding of the topics discussed could help my own comprehension of the material.

This entry focuses on some basic vocabulary used in the project management side of agile practices.   The vocabulary presented here concentrates on requirement gathering, describing deliverables and estimation and will be used in later articles in this series.

My Experiences

The game team I am currently on use scrum (though purists would called it “scrum but”) which is common methodology adopted for managing time on an agile project.  I have myself used “agile” style development practices like unit testing and continuous integration (using NUnit, Cruise Control .Net and Trac) in my past life outside of the games industry.  I have made sure to make time to read about these agile practices for years.

Most of the week beginning 8th of February 2009 I took part in a lab called Agile Development in C# and I had a glimpse of techniques used in teams around the mother-ship.  Spending the week building a project, managing the backlog and taking turns at being the scrum master and team lead was a very educational experience.  “Living it” with guidance in this way was like a crucible of learning (there was an element of competition too).  It was very rewarding yet quite draining!

My current lead developer attended the same course – thus I am more confident about “buy-in” of some agile practices at that level because of the extra common ground that brought me.  I have already had the opportunity to apply some development techniques discussed in that course to the main code base I work with day to day.

Vocabulary: User Stories

User stories are requirements written from the perspective of the customer.  A collection of user stories make up the “product backlog” and can be prioritised by how important they are to the user.  This allows the developer to concentrate on things that would be immediately useful to the customer for when a vertical slice of the product is delivered at the end of the “sprint”.

A user story is an expression of what they want and why, rather than any technical detail of the how.

A good example might be: “I would like my lawn to be short so it is pleasant to lay back and read in the garden.”

A poor example might be: “Mow lawn to 2 cm using a rotary petrol mower.”

The user stories concentrate on requirement gathering and intent.  These stories help communicate how the development team understand the requirements.  They also allow quick feedback from the user on any good or bad assumptions made.

Vocabulary: Story Points

Story points were introduced as a way of quantifying an estimate of a user story.  Where as estimates are usually expected as a duration, story points are based on an estimation of size and complexity.

For example a gardener might want to estimate the size of the lawn, see how overgrown it is and how much edge work would be necessary to keep it neat before attempting to estimate a time.  Depending on weather conditions on the day, it may even take slightly longer on some days than others.

The customer expects a regular fee and period of time spent in the garden rather than taking in to account difficulties from one week to the next.  One week the garden may not have grown very much and the whole thing will be quicker to complete.  Perhaps the gardener might take the time to make nice little extra touches to the garden to add value that easier week where there is ample time left over.

So a story point is not directly translatable to time because of the various unknowns.  The number of story points against something keeps track of how much effort will be required – something with more story points is harder to complete.

Vocabulary: Tasks

Tasks are derived from breaking a user story down in to small chunks of functionality.  These tasks are estimated in hours (or story points).  The estimated time remaining is updated daily during the scrum.

A task is only counted as “done” when it is verified.  A consistent measurement of “done” is important so it can be signed off for the sprint.  Quality gates can be used to measure if something is actually complete.  This could include passing tests and automated code quality tools.

Once all the tasks for a user story have been completed, functionally tested and verified, then it can be taken from the product backlog.

For example tasks for large garden could be (in the form of Task (verify) – duration):

  • Mow lawn (lawn appears visibly shorter.  Regular straight lines can be seen in the grass) – 2 hours
  • Tidy garden and rake lawn (no debris can be seen on the lawn or path, grass cuttings bagged and loaded) – 1 hour

Vocabulary: The Daily Scrum

The Daily Scrum is often a short morning stand-up meeting only including people doing the work itself.  The scrum master role can be taken up by any member of the team.  The scrum master asks the questions:

  1. What did you do?
  2. What will you do today?
  3. What is blocking you?

The estimates are updated on the current tasks, and the scrum master goes about trying to unblock the team where they are blocked.  Blockages could be something technical, through to waiting on another team to complete a task.

Continuing the gardening example – if the gardeners have noticed the lawn mower blades have become blunt and causing the team to slow down, it would be up to the scrum master to communicate with the tools team and ask them to sharpen the lawn mower blades.

Vocabulary: Sprints

A selection of user stories are chosen for the sprint.  Stories can be added or dropped from a sprint, but the deadline for a deliverable does not change.  If the deliverable, demonstrable version of the software is created ahead of time and the team feels confident they can take another story from the backlog and if it’s too big, break it down where possible.

The idea of a sprint is to always have something to show for the work everyone has done at a regular interval, to allow the users to feed back.  At the point a sprint begins, the requirements of the stories they are working on are locked.  A sprint can be completely aborted, or a story dropped… but the requirements of an existing story should not change.  The motivation is that the team are not aiming for a moving target and can concentrate on getting the unit of work done.

Ideally each sprint delivers a vertical slice to show progress.  For the running gardening example I have been using – this might be completing the more simple front garden entirely to prove the gardeners have understood the requirements sufficiently to maintain the garden to the customer expectations.  It also gives the customer an opportunity to feedback or change their mind “actually, I want my lawn to have circles rather than lines”.

Vocabulary Cheat Sheet

Daily Scrum Short stand-up meeting.  What did you do?  What will do today?  What is blocking you?
Product backlog Prioritised list of user stories.
Quality gate Checklist of things to verify work against before it is counted as completed.
Scrum master Leads daily scrum.  Tracks work completed and remaining, and organises removal of things blocking the team.  Ideally a role rotated between members of the team.
Sprint A period of time where user stories are chosen to work on.  External influences are not allowed to change the requirements of the stories being worked on.  Sprints are a fixed length, but stories can be postponed or additional ones taken from the backlog.
Story points Unit of estimation measuring complexity.
Task A user story can be broken down in to one or more tasks.  Tasks are estimated daily in hours (or story points) remaining by the developer working on them.
User stories User requirements expressed in sentences from the customer perspective.
Vertical slice Showing off a feature in an application that works from start to finish but may be limited in scope.  For example a rope bridge crossing a chasm is immediately useful and allows people to cross.  Having that in place can help to build a better bridge later.

References

Some of my references are company confidential and cannot be shared here – the web is full of useful information though.  The sites below are useful launch pads to further reading.

EDIT: Thought of a few more references:

Please comment any useful links you have stashed away :-)


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