Agile Use Cases Writing Effective Use Cases meets

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Agile Use Cases ( Writing Effective Use Cases meets Agile Software Development ! )

Agile Use Cases ( Writing Effective Use Cases meets Agile Software Development ! ) Alistair Cockburn Humans and Technology acockburn@aol. com http: //Alistair. Cockburn. us Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 1

Can use cases be agile? (Can you be agile with use cases? ) Yes

Can use cases be agile? (Can you be agile with use cases? ) Yes Do use cases contradict Agile ? : Use cases / not use cases / value of use cases vs stories : Agile / not agile / value of agile When should we use agile use cases ? : document faster, later, cheaper, : plan on changing your mind along the way, : always. Detecting and exercising available dimensions of freedom : Write less, more clearly (tips). : Shortcut process & use case structure. . . (tips, tradeoffs) : Tools Q&A Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 2

Coming from agile non-use-cases to agile UCs is easier than coming from non-agile UCs

Coming from agile non-use-cases to agile UCs is easier than coming from non-agile UCs Overly complex use case writing is hard to change, tied to overly complex process (hard to change!) Already understanding Agile means : already have a lighter process : already have mindset to simplify the writing : --> leads to agile use case writing. Need to understand : (A) Simple use cases : (B) Agility as energy savings Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 3

Part 1: What is / isn’t a use case (good for) Alistair Cockburn ©Humans

Part 1: What is / isn’t a use case (good for) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 4

Good use cases aren’t Text No GUI No data formats 3 - 9 steps

Good use cases aren’t Text No GUI No data formats 3 - 9 steps in main scenario Easy to read At user’s goal level Record of decisions made UML use case diagrams describing the GUI describing data formats multiple-page main scenario complicated to read at program-feature level tutorial on the domain Use cases *can be* written -all up front --or-- just-in-time each to completion --or-- in (usable) increments Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 5

Robert Martin: “It shouldn’t take longer than 15 minutes to teach someone how to

Robert Martin: “It shouldn’t take longer than 15 minutes to teach someone how to write a use case!” Use case: Text describing scenarios of user succeeding or failing to achieve goal. (goal of primary actory) “Place an order” (level of goal [summary, user, subfunction]) (primary actor) (User goal / Clerk) (action steps: full sentences showing Main scenario: who takes the action! 1. Clerk identifies customer, item and quantity. 3 - 9 steps long. ) 2. System accepts and queues the order. (condition causing different actions) Extensions: 1 a. Low credit & Customer is ‘Preferred’: System gives them credit anyway. (action step(s) handling those conditions) 1 b. Low credit & not ‘Preferred’ customer: Clerk accepts only prepayment. 2 a. Low on stock: Customer accepts rain-check: Clerk reduces order to available stock level. Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 6

Good use cases aren’t Text No GUI No data formats 3 - 9 steps

Good use cases aren’t Text No GUI No data formats 3 - 9 steps in main scenario Easy to read At user’s goal level Record of decisions made UML use case diagrams describing the GUI describing data formats multiple-page main scenario complicated to read at program-feature level tutorial on the domain Use cases *can be* written -just-in-time --or-- all up front in (usable) increments --or-- each to completion (more Agile) Alistair Cockburn (more common) ©Humans and Technology, Inc. , 2000 -2003 Slide 7

Use cases summarize end-user experience, not programmers tasks. 1980’s: Let’s write requirements in features!

Use cases summarize end-user experience, not programmers tasks. 1980’s: Let’s write requirements in features! : User’s don’t understand. . . user pressure to write in use cases. . . 1990’s: Let’s write requirements in use cases! : Programmers’ work units are features, not use cases. . . programmer pressure to write in features. . . 2000: So let’s write requirements in features! : FDD & XP user stories. . . lose the end user experience again. . . A pendulum of features vs. use cases Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 8

Use cases have strong & weak points (as anything) 1. Use cases hold functional

Use cases have strong & weak points (as anything) 1. Use cases hold functional requirements in an easy-toread text format 2. They make a good framework for non-functional requirements & project scheduling. 3. Use cases show only the Functional req’ts. 4. Design is not done only in use case units. Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 9

Use cases do not collect formulae, state, cardinality, performance, uptime, . . . Examples:

Use cases do not collect formulae, state, cardinality, performance, uptime, . . . Examples: 1. Order cost = order item costs * 1. 06 tax 2. Promotions may not run longer than 6 months. 3. Customers only become Preferred after 1 year. 4. A customer has one and only one sales contact. 5. Response time is less than 2 seconds. 6. Uptime requirement is 99. 8%. 7. Number of simultaneous users will be 200 max. Capture those in any form available, *somewhere* in your requirements files ! Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 10

Goals make a good structure on which to hang requirements & project details. Project

Goals make a good structure on which to hang requirements & project details. Project planning capitalizes on goal structure: : Useable Releases. : Priorities, : Schedule, staffing Name Update customer Scan products Generate invoice Funds transfer P. Actor Customer Finance Pr. high med Diff. med high Release 1 1 3 4 (Note: spreadsheets are perfect for this!) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 11

Use cases provide 4 values to the project at different times: 1. The list

Use cases provide 4 values to the project at different times: 1. The list of goal names provides executives: : Shortest summary of what system will contribute : Project planning skeleton (priorities & timing) 2. The main success scenario provides all: : Agreement as to the system’s responsibilities 3. The extension conditions provide programmers: : List of things programmers have to watch for : List of things analysts have to investigate 4. The extension handling steps provide dev’t team: : Record of (tricky) business policy decisions Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 12

The hard parts about use cases is not typing, but thinking and agreeing. •

The hard parts about use cases is not typing, but thinking and agreeing. • Total time : ~ 3 days construction : ~ 2 hours typing : 2 -3/4 days spent thinking, arguing (over policy). 1. Is each step correct? 2. Are there any system responsibilities between steps? 3. Are there any outside systems this system should use? 4. Are there any other stakeholders whose interests we missed? 5. Did we catch every extension condition? (The programmers will (maybe)) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 13

Don’t try to teach a tutorial on the subject domain within the use cases!

Don’t try to teach a tutorial on the subject domain within the use cases! In any text, receiver must always jump a gap. : Experts jump larger gaps : Novices jump smaller gaps. To teach a domain, you need a textbook, not use cases. : Textbooks use smaller gaps. : Think of use cases as “documenting decisions”, not “teaching the domain. ” Target the gap for the people: “sufficient” communication with a “small-enough”gap. : More experienced people need less writing ! Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 14

Part 2: What is / isn’t agile development (good for) Alistair Cockburn ©Humans and

Part 2: What is / isn’t agile development (good for) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 15

(3 -1/2) History: How did “agile” arise? “Agile” techniques were in use since the

(3 -1/2) History: How did “agile” arise? “Agile” techniques were in use since the beginning. Agile (mobility-based) techniques did not show competitive advantage in the 1970 s / 1980 s, but did during the 1990 s and do now. 1994: trials of semi-formal agile methodologies RAD DSDM XP Crystal Scrum Adaptive Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 16

(4 -1/2) Development approaches are only attitudes, “centering of the attention”. Declarations of core

(4 -1/2) Development approaches are only attitudes, “centering of the attention”. Declarations of core values declare an “attitude” An attitude cannot promise success in the future, it can only be spoken successfully in the past tense. it is only a wish to be a certain way A would-be agile process A would-be predictable process A would-be repeatable process A would-be inexpensive process Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 17

2001 Agile Software Development Manifesto - a declaration of values “We are uncovering better

2001 Agile Software Development Manifesto - a declaration of values “We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value: : : Individuals and interactions over Processes and Tools. Working software over Comprehensive documentation. Customer collaboration over Contract negotiation. Responding to change over Following a plan. That is, while there is value in the items on the right, we value the items on the left more. ” (Kent Beck, Mike Beedle, Arie van Bennekum, Alistair Cockburn, Ward Cunningham, Martin Fowler, James Grenning, Jim Highsmith, Andrew Hunt, Ron Jeffries, Jon Kern, Brian Marick, Robert Martin, Stephen J. Mellor, Ken Schwaber, Jeff Sutherland, Dave Thomas ) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 18

Agile development works because software development is an economic game Economic consequences to each

Agile development works because software development is an economic game Economic consequences to each choice. : Less is usually better. . . “sufficient” is enough. (Project success factors reviewed: ) (Agility resides Here!) Nourishment Citizenship Communication Focus Increments (Includes developers AND users!) Skills Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 19

The “iron triangle” isn’t a triangle at all -“Process” is the 4 th dimension

The “iron triangle” isn’t a triangle at all -“Process” is the 4 th dimension ! Agile = shortcutting the process (cheating legally to win) Scope Process Time Resources (Some people use agile to handle late-breaking requirements changes, I use it to improve development efficiency) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 20

Agile development: short circuiting process steps without compromising final product. • Focus on *early*

Agile development: short circuiting process steps without compromising final product. • Focus on *early* & *frequent* delivery of *useful* software to real users using *just-in-time* techniques. • Focus on *feedback* loops at all levels : (requirements design code test communication. . . ) • Replace fanfare around the process with people checking in with other people. • *Talk* to users / sponsors, find out what they need! • Adjust your working habits *monthly or quarterly* to fit your particular situation! Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 21

The Agile attitude focuses on: 1. Talent & Skill (fewer better people) 2. Proximity

The Agile attitude focuses on: 1. Talent & Skill (fewer better people) 2. Proximity (developers - users) 3. Communication (morale, daily standup) 4. Just-in-time requirements and design 5. Frequent Delivery (incremental development) 6. Reflection 7. Less paper, more tacit / verbal communication 8. Tools 9. Quality in work 10. Different strategies for different projects Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 22

Good agile development is / does isn’t / doesn’t Efficient Lots of “just in

Good agile development is / does isn’t / doesn’t Efficient Lots of “just in time” Adjust to circumstances (Re)Plan regularly Lots of person-to-person comm. Adaptively cut fat in the process hacking Giant Energy Up Front (GEUF) only XP (XP is one alternate) plan-less People sitting in isolation rigid adherence Agility *can* Be heavier or lighter, depending on circumstances Use various requirements techniques (e. g. , use cases, stories, features) In agile development we value following the principles over following specific practices ! Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 23

Is / Isn’t: Misconstruing the message 1. Agile SD is cheating 2. Agile SD

Is / Isn’t: Misconstruing the message 1. Agile SD is cheating 2. Agile SD requires the best developers 3. Agile SD is hacking 4. Agile SD won’t work for all projects Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 24

1. Agile techniques are “cheating”. · · · Hire good people; Seat them close

1. Agile techniques are “cheating”. · · · Hire good people; Seat them close together to help each other out; Get them close to the customers and users; Arrange for rapid feedback on decisions; Let them find fast ways to document their work; Cut out the bureaucracy. This is: cheating stacking the deck a good idea the heart of agile software development Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 25

2. Agile only works with the best developers. Every project needs at least one

2. Agile only works with the best developers. Every project needs at least one experienced and competent lead person. (Critical Success Factor) Each experienced and competent person on the team permits the presence of 4 -5 “average” or learning people. With that skill mix, agile techniques have been shown to work many times. Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 26

3. Agile is hacking. (Hacker interpretations are inevitable. ) Hackers: “. . . spend

3. Agile is hacking. (Hacker interpretations are inevitable. ) Hackers: “. . . spend all their time coding” Agilists: . . . test according to project priorities, recheck results with users often. Hackers: “. . . talk to each other when they are stuck” Agilists: . . . talk to each other and customers as a matter of practice. Hackers: “. . . avoid planning” Agilists: . . . plan regularly Hackers: “. . . management caves in out of fear” Agilists: . . . expect management to provide priorities, & participate jointly project adjustments. Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 27

(5 -6/6) 4. Agile won’t work for all projects. Right. (Business isn’t fair). Agile

(5 -6/6) 4. Agile won’t work for all projects. Right. (Business isn’t fair). Agile is an attitude prioritizing: Project evaluation based on delivered code Rapid feedback People as a value center Creativity in overcoming obstacles Not every team. . . values the Agile value set. . can set up the needed trust and communication Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 28

Lighter-agile vs. Heavier-agile : Light is good, but has limits # people needed more

Lighter-agile vs. Heavier-agile : Light is good, but has limits # people needed more people fewer people Heavy methodology Light methodology Problem Size Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 29

Criticality (defects cause loss of. . . ) Suit the process to the occasion

Criticality (defects cause loss of. . . ) Suit the process to the occasion project size & priorities, system criticality. . . Prioritized for Legal Liability Prioritized for Productivity & Tolerance Life (L) L 6 L 20 L 40 L 100 L 200 L 500 L 1000 Essential money (E) E 6 E 20 E 40 E 100 E 200 E 500 E 1000 Discretionary money D 6 (D) D 20 D 40 D 100 D 200 D 500 D 1000 C 20 C 40 C 100 C 200 C 500 C 1000 Comfort (C) C 6 1 -6 - 20 - 40 - 100 Number of people Alistair Cockburn - 200 - 500 - 1, 000 involved +20% ©Humans and Technology, Inc. , 2000 -2003 Slide 30

Productivity: (Flux & Uncertainty) Reality Check: Work as parallel & light as project features

Productivity: (Flux & Uncertainty) Reality Check: Work as parallel & light as project features and personalites permit. Project requires at least this much productivity to succeed old-school projects e-projects Where is your group, your project on this graph? ? Group’s tolerance for ambiguity / uncertainty Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 31

Part 3: Agile-ly generating agile use cases Alistair Cockburn ©Humans and Technology, Inc. ,

Part 3: Agile-ly generating agile use cases Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 32

Core elements to using use cases *agile-ly* increments, just-in-time, close communication • Write just

Core elements to using use cases *agile-ly* increments, just-in-time, close communication • Write just enough use case content to plan to the needed planning horizon : Long (project) horizon -> just use case names or briefs. : Short (iteration) horizon -> extension handling. • Just barely beat the programmers to the extension handling decisions (just in time) • Write just enough content for the team to understand. • *Show* UCs, system to users/sponsors, get feedback! • Adjust your working habits *each iteration* to fit your particular situation! Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 33

Core elements to using use cases *agile-ly*: increments, just-in-time, close communication Ask, • How

Core elements to using use cases *agile-ly*: increments, just-in-time, close communication Ask, • How much do we need to write at this time? • When do we need to write more? • What is the fastest way to write/convey them? • Who benefits from more information or more detail? Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 34

Take advantage of available degrees of freedom in the process 1. Write less more

Take advantage of available degrees of freedom in the process 1. Write less more clearly (always) 2. Write less (sometimes) 3. Shortcut the use case structure (sometimes) 4. Write later & shortcut the process (usually) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 35

1. Write less more clearly (always) Text No GUI No data formats 3 -

1. Write less more clearly (always) Text No GUI No data formats 3 - 9 steps in main scenario Easy to read At user’s goal level Record of decisions made UML use case diagrams describing the GUI describing data formats multiple-page main scenario complicated to read at program-feature level tutorial on the domain (shorter, more economic & more readable!) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 36

2. Write less (sometimes) (the economics of communication) • Fully dressed use cases •

2. Write less (sometimes) (the economics of communication) • Fully dressed use cases • Casual use cases • Use case briefs The correct form to use depends on your project’s priorities and properties ! Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 37

Economics of communication: Fully Dressed (expensive, complete) Use Case 12. Buy stocks over the

Economics of communication: Fully Dressed (expensive, complete) Use Case 12. Buy stocks over the web Primary Actor: Purchaser (user) Scope: PAF Level: user goal Precondition: User already has PAF open. Guarantees: sufficient log information exists that PAF can detect what went wrong. Success Guarantees: remote web site acknowledged purchase, user's portfolio updated. Main success scenario: 1. User selects to buy stocks over the web. 2. PAF gets name of web site to use (E*Trade, Schwabb, etc. ) 3. PAF opens web connection to the site, retaining control. 4. User browses and buys stock from the web site. 5. PAF intercepts responses from the web site, and updates the user's portfolio. 6. PAF shows the user the new portfolio standing. Extensions: 2 a. User wants a web site PAF does not support: 2 a 1. System gets new suggestion from user, with option to cancel use case. 3 a. . Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 38

Economics of communication: Casual (less expensive, less complete) Buy something (Purchaser / user-goal level)

Economics of communication: Casual (less expensive, less complete) Buy something (Purchaser / user-goal level) The Requestor initiates a request and sends it to her or his Approver, who completes the request for submission and sends it to the Buyer. The Buyer finds the best vendor, initiates PO with Vendor. At any time prior to receiving goods, Requestor can change or cancel the request. Canceling it removes it from any active processing. Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 39

Economics of communication: Brief (inexpensive, just a short note) Actor Goal Brief Description .

Economics of communication: Brief (inexpensive, just a short note) Actor Goal Brief Description . . Production Staff Prepare digital cartographic source Convert external digital data to standard format, validate & correct in preparation for merging with operational database. . (Note: spreadsheets again!) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 40

3. Shortcut the use case structure (sometimes) Use cases are not read by a

3. Shortcut the use case structure (sometimes) Use cases are not read by a compiler but by a human. . . --> so, Don’t be rule-bound, but adapt the form to your needs. Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 41

Test department needs detailed requirements. Development can usually use agile ones. [Alistair’s generic process

Test department needs detailed requirements. Development can usually use agile ones. [Alistair’s generic process model] (Shorter, cheaper, easier to read, more stable (agile) use cases) Usage expert (Development department) R Use cases Domain expert Data formats D UI descr. R D Program Tests (Test department) (Detailed, expensive, long, tedious, brittle use cases) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 42

4. Write later and shortcut the process (usually) Use cases *can be* written -just-in-time

4. Write later and shortcut the process (usually) Use cases *can be* written -just-in-time --or-- all up front in (usable) increments --or-- each to completion (more common) (more Agile) Use the “Validation V” view of increments Req'ts Validate req'ts Design Code Alistair Cockburn Validate logic Validate syntax ©Humans and Technology, Inc. , 2000 -2003 Slide 43

Project horizon -> all use case briefs or casual Iteration horizon -> full use

Project horizon -> all use case briefs or casual Iteration horizon -> full use case, just-in-time S (all UCs, ultra-light content, estimation purposes) Full Project (just-in-time, complete) Iteration S (10 more use cases) (10 use cases) E Alistair Cockburn E E E ©Humans and Technology, Inc. , 2000 -2003 E E Slide 44

Finally, Tools: Choose for the value it delivers, not for its popularity • List

Finally, Tools: Choose for the value it delivers, not for its popularity • List of UCs for project planning & status: : Spreadsheets are very effective : Lotus Notes medium effective • Main success scenario for agreement: : Flipcharts in meeting good for fast disagreement : Word processor (Lotus Notes) quite effective • List of extension conditions for completeness: : Word processor quite effective : Flipcharts in project room? (untried) • Extension handling steps for policies: : Word processor very effective : Wiki technology? (http: //c 2. com) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 45

Summary of Agile Use Cases • User’s goal level - Text - 3 -9

Summary of Agile Use Cases • User’s goal level - Text - 3 -9 -step main scenario No GUI - No data formats - Easy to read Record of decisions made (not a tutorial) • Write briefs and casuals to estimate & plan project Write full use cases just-in-time per iteration • Just-in-time = extension-handling decisions made before the programmer gets around to asking for them. • Spreadsheets good for briefs, planning activities. Focus on communicating, not filling templates Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 46

(1) In 10 minutes: Write a use case for a clerk entering a video

(1) In 10 minutes: Write a use case for a clerk entering a video rental into the computer. ( Write the basic dialog between the clerk and the system, Name all the things that could go wrong during the procedure. ) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 47

(2) In 10 minutes: Name all the use cases for a video rental store

(2) In 10 minutes: Name all the use cases for a video rental store computer system. ( List every person who will use the computer system. For each person, list every reason they have to use the system. ) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 48

(3) In 5 minutes: Prioritize the list of UCs (order in which to develop

(3) In 5 minutes: Prioritize the list of UCs (order in which to develop & deliver them). ( Rank for when it is *really* needed, by dependency or business payback. ) Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 49

Agile Use Cases Alistair Cockburn Humans and Technology acockburn@aol. com http: //Alistair. Cockburn. us

Agile Use Cases Alistair Cockburn Humans and Technology acockburn@aol. com http: //Alistair. Cockburn. us Alistair Cockburn ©Humans and Technology, Inc. , 2000 -2003 Slide 50