18 January

Writing a Functional Spec

Administrivia

How many teams will want departmental web space vs links to your own space?

Please send me your CS ids Names for your projects

The Plan Quick Pass on the Software

Engineering Process (next week) Context on what you are doing

Focus on specifics that you need for your deliverables

Back up to higher level discussions and more enterprise-oriented options

Today: toward the functional spec

Software Engineering Fundamental Steps

Requirements Design Implementation Integration Test

Requirements Analysis To build something, we first must

understand what it is we’re building

Establish expectations Understandable by both the client

and the developer

Why Written Requirements? Unambiguous Defines goals Cost of finding a requirements bug

later can be 100 times more expensive ‘99 weather satellite where used

wrong units (metric vs. feet)

Our Requirements Phase

What does the client want to do? User stories – his (or her) terms Use cases – your terms

Extract the essence: requirements Translate to a system: functional

spec

Talking to the client Active listening

Restate what you hear How to extract information

Ask them to “tell stories” Focus on the interface: that’s what

the user sees Start the design process with the

customer Draw pictures!

User Requirements

Identify the user groups Understand their goals Determine the total user experience How users perform their tasks now

Task and goal descriptions, importance ranking, strategies, measures, and targets

Stories and scenarios describing how they currently perform their tasks

User Requirements - Persona A description of a fictitious user representing a

distinct user group User groups are based on unique goals Each persona represents a unique set of goals for

design Personas help direct the design

Allow designers to focus on people’s needs and differences

Skills, motivations, emotions, behaviors Use each persona as though it were a real person

“What would Jackie do if …”

Persona excerpt from hotel reservation system

Persona: Robert

“Everything had best run like clockwork.” – Robert

Robert – Director of Field Operations Company: Stewart Auto Glass Citizen of Great Britain 45 years old Degrees: BS Industrial Engineering Personal concerns: being responsible and do everything with integrity Corporate concerns: transforming Stewart Auto Glass into a premier auto industry supplier Robert is responsible for all field operations, including glass installation at fourteen auto manufacturer’s plants as well as the over 350 nationwide auto-glass retail outlets owned by Stewart Auto Glass. Robert loves the highly active work environment and the demands of the job. He thrives on rapid-fire situation management, in which he demonstrates his quick analytic ability and decisive management style. Robert travels frequently and expects the same degree of precision, reliability, and integrity from the travel industry as he expects from himself and his own organization. He is a discerning and demanding business traveler. He and his wife are avid golfers and he sometimes combines pleasure with his business duties, but always after all business has been successfully completed. He shoots in the high 70’s, making a point of being very good at whatever he chooses to undertake, in business as well as his personal life.

Story excerpt Scenarios / stories that clearly communicate and demonstrate the users’ requirements Business Traveler: Robert makes a hotel reservation Robert needs to be in Boston for a two-day business meeting. Robert travels frequently, typically several times a month, but he's still conscientious about finding discounted flights and cars whenever possible. He won't bend on the hotel though, even if a discount is available. He likes his comfort, and will pay for it. Robert has traveled to the same seven cities for about four years, and has developed a routine. He has a favorite airline and hotels in each city. He always stays at high-end hotels, usually in rooms with in-room business facilities. He usually rents a car but will take a taxi if the weather is going to be bad. Robert typically prefers to make his own reservations via the Web - he’s a stickler for having everything go exactly as planned, and he doesn’t quite trust that a travel agent will be as exacting as he is. Robert finds a few free minutes at the office, so he accesses the ExpressTravel Web site, which is the one he usually uses. For some reason, the Web site is down, so he goes to the UTravel Web site. He doesn't like this Web site as much and has only used it once before, but, at this point, he has no option. He needs to get his reservations made. On the home page he takes advantage of the “create your own trip” window and types in his departure and arrival city, dates of travel and preferred departure and return times. Robert clicks the small icon of the calendar to check the exact dates of his trip. He is asked to specify if he has a preferred airline, class of travel, a preferred time of day, number of travelers, and number of connections preferred. After typing in all of this information, he clicks the Search button. He's frustrated because the next page tells him there are several matches for Chicago, IL airports and he needs to specify the correct airport. He clicks on ORD then he clicks on the "Search Now" lin

User Interfaces as a Requirements-Gathering Tools

User Knowledge and experience Age and gender Physical handicaps Characteristics of tasks and jobs Psychological characteristics

Function Menu design: what’s the natural order? Types of controls: what’s the natural

mechanism?

Use Cases

A statement of the functionality users expect and need, organized by functional units

Functional units are any natural division

Relationships between user roles and use cases

User activities, decisions, and objects involved

Documenting Use Cases

UML diagrams are often used Requires tools Will discuss later, not use for now

We will use simple text description Examples from last year

Butterfly Lab Foreign Language Resource Center

A requirement must be … documented expressed precisely expressed as what, not how prioritized

essential, desirable, optional primary, secondary, tertiary

testable

The set of requirements must be…

ConsistentThree requirements:

Only basic food staples will be carried Everyone will carry water Basic food staples are flour, butter, salt, and

milk

CompleteThe function tells whether 3 numbers produce an equilateral, isosceles, or scalene triangle.

Types of Requirements Functional: services that the

application must provide Performance: speed, capacity, memory Reliability and availability: failure rates Error handling: how to handle Interface: user and program Constraints: systems or tolerances (Inverse requirements: what it won’t

do)

Requirement Level Often addressed in two phases

Customer level Developer level (will visit later)

Once agreement exists with customer, developer “translates” them into his language

Example User must never lose more than 10 minutes of

work Autosaving is required

Sources of requirements People

Broad range of stakeholders Conflicting requirements Wants and needs Helping the customer articulate the

requirements: use cases Hardware constraints

Laws of physics and nature Social responsibility

Sources of Requirements: People vs. Other

(Brackett, CMU)

Relatively highRelatively low % of requirements gathered from people

Typ

e of

ap

plic

atio

n

highly constrained

unconstrained

missile guidance system

flight control system for airliner

enhancement to corporate accounting system

manufacturing control system

corporate accounting system

video game

decision support system for military tactics

What is a Functional Spec? Describes the features of the software

product Describes the product's behavior as

seen by an external observer Contains the technical information and

data needed for the design Defines what the functionality will be,

but not how it will be implemented Brooks’s architecture

What is an Architecture? Complete and detailed

specification of the user interface(Brooks, The Mythical Man-Month)

Architecture: what happens; implementation: how it is made to

happen(Blauuw)

Architecture Example Non-digital clock Architecture = {face, hands, running

mechanism} Implementations = watch, grandfather

clock, wall clock, …