Scenarios in Requirements Discovery

A scene has a beginning state and a finish state

¡  But there could be multiple ways to get from A to B

A scenario is one way for a scene to play out sce·nar·i·o [si-nair-ee-oh, -nahr-] noun, plural sce·nar·i·os. 1. an outline of the plot of a dramatic work, giving particulars as to the scenes, characters, situations, etc. 2. the outline or the manuscript of a motion picture or television program, giving the action in the order in which it takes place, the description of scenes and characters, etc. 3. an imagined or projected sequence of events, especially any of several detailed plans or possibilities: One scenario calls for doubling profits by increasing our advertising, the other by reducing costs. Source: Random House Dictionary

Building scenarios expose new requirements

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There are four types of scenarios ¡ Normal ¡ Alternative ¡ Exceptions ¡ What-if

Normal scenarios are also known as the happy path

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Alternative scenarios are other ways to get to the end

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Exceptions are errors

What-if scenarios

We should always start with the happy path

Then identify alternative scenarios using questions ¡ Does this always happen as in the happy path? ¡ Do we know the precise meaning of each noun and verb? ¡  Is there any missing data? ¡ Are there any subjective judgments? ¡ What assumptions am I making? ¡ Does this make sense to me?

You find exception cases by identifying errors

What _______ exceptions would make it impossible to succeed? ¡ Data ¡ Physical ¡ Human

Lastly, find some what-if scenarios by removing constraints and brainstorming For example:

Our step is … "Customer telephones asking for a taxi"

What is our constraint? He uses a phone

Remove that constraint He contacts us somehow

So exactly how, then? He could email, hit the website, text us, tweet, walk in, CB radio, put an ad in the paper

Re-evaluate identifying what is in-scope and what is out-of-scope

In scope: email, web, text, walk-in. Out of scope: Twitter, CB, paper

So how do you build scenarios? ¡  Text scenarios ¡  Storyboards ¡  Scenario process models ¡  Scenario playthroughs

Text scenarios are the most common scenario-building tool

Storyboards are great for building the user interface

Scenario process models focus on the data flow

Scenario playthroughs are role-playing

Conclusion ¡  Scenarios tell a story – one story – of how to

accomplish a business goal ¡  There are several types ¡  Main scenario ¡  Alternate scenario ¡  Exceptions ¡  What-ifs

¡  They should be discovered and fleshed out in that orde