why we need a granularity concept for user stories...rq3: is it possible to control eid by splitting...

Why We Need a Granularity Concept for User Stories

Olga Liskin, Raphael Pham, Stephan Kiesling, Kurt Schneider

Software Engineering Group

University of Hannover, Germany

User Stories

•  Heart of Agile Methods •  Describe small user-oriented parts •  Guide daily work – Help clarify requirements – Show what to implement next – Help with planning & monitoring progress

Olga Liskin -‐ User Story Granularity 2

How can we make good user stories?

Which guide daily work Which help to communicate with customer


Many things on how to write good User Stories But how about what we put in? Difference:


As a Basketball Coach I want to buy Sports gear to equip my

team.

As a Basketball Coach I want to be able to select all different sizes I need of a specific

product I chose

Granularity

„extent to which a larger entity is subdivided“ (Wikipedia)


Important CharacterisJc of User Stories

Let‘s invesJgate that!

Should be taken more into account when working

with User Stories

Granularity


clear vs.

vague

concrete vs.

abstract

small scope vs.

large scope This is it

Expected Implementa.on Dura.on (EID)

EsJmated Jme (in days) that a developer or pair will need to

implement a story

Research Questions

Goal: Characteristic which helps improve User Stories


RQ1: Is EID easy to measure?

RQ2: Which actual EID values do user stories in current projects have?

RQ3: Is it possible to control EID by splitting user stories?

RQ4: Is EID a relevant factor for user stories?

Survey

•  Sent out to 600 GitHub-Users •  53 usable answers – 41 participants reporting about industrial

projects they work on – 12 participants reporting about private projects


RQ1 – Easy to measure?

•  49% consider implementation duration when rating a user story

•  55% claimed they could assess implementation duration if necessary

•  Over-/underestimation:


RQ2 – Actual EID Values

19%

24%

25%

19%

13%

a few hours 1 day 1-‐3 days 4-‐5 days > 1 week


Distribute 100 points: which implementaJon duraJons to User Stories you typically work with have (3400 points total)

If your user story is 3 days long, it means

the customer doesn‘t understand for 3 days what‘ s

going on!



In more detail: Percent of the quesJonees who have allocated x or more points to certain story sizes



In more detail: Percent of the quesJonees who have allocated x or more points to certain story sizes Half of our

quesJonees say: 30% or more of our stories take more

than 4 days

RQ3 – Splitting Stories to Control EID


Could a user story with the given EID be split into smaller stories?

RQ3 – Splitting Stories to Control EID


Could a user story with the given EID be split into smaller stories?

However, a problem emerged:

At some point, a story gets so small that it has no more value for

the customer

RQ4 – EID relevant?


Larger Story leads to ....

Communication

One has to change more details aaerwards

it takes longer until one can gather feedback about this story

more probable that one develops more than what was expected

it is harder to meet thecustomer's requirements

RQ4 – EID relevant?


Smaller Story leads to ....

Tangibility

our estimation of how long the story will take is more precise

I can estimate better how many code parts I will have to touch in order to implement it

I can estimate better with how many other developers I will have to talk

it will less often grow unexpectedly in time/complexity

Small esJmaJon because of lacking

knowledge

Take granularity into account when doing

planning!

Conclusions & Outlook


If a User Story is larger than one day, you should split it!

If a User Story has a very small es.ma.on,

be careful

Small step towards finding out about user

story granularity

Concrete values?

Customer‘s perspecJve?

More Outlook

User Stories relatively fine grained Sometimes we need coarsely grained requirements artifacts Be part of the User Story story! I‘m looking for experiences & opinions: [email protected] @o_liskin


why we need a granularity concept for user stories...rq3: is it possible to control eid by splitting...

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