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AUInterface Analysis

Professor J. Alberto Espinosa

Business Requirements AnalysisITEC-455 Spring 2010

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Objectives• Discuss basic issues about

interface analysis

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Interface

“The place at which independent and often unrelated systems meet and act on or communicate with each other” – Webster dictionary

Software

Network

Software

Hardware UserSystem

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ATM System

Customer

Bank Manager

ATM Service Rep

Customer Accounts System

Withdraws Funds

Makes Deposits

Manages Account

Inquires CustomerActivity

Monitors ATMStatus

Replenishes Cash

Upload CustomerTransaction

Data

Use Case Diagram without Interfaces

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ATM System

Customer

Bank Manager

ATM Service Rep

Customer Accounts System

Withdraws Funds

Makes Deposits

Manages Account

Inquires CustomerActivity

Monitors ATMStatus

Replenishes Cash

Upload CustomerTransaction

Data

WithdrawalInterface

Deposit Interface

AccountManagement

Interface

Customer ActivityInquiry Interface

ATM StatusMonitor Interface

CashReplenishment

Interface

CustomerAccounts System

Interface

Use Case Diagram with InterfacesEx.1: 1 Interface per each Actor-UC Interaction

UML Symbolfor Interface

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ATM System

Customer

Bank Manager

ATM Service Rep

Customer Accounts System

Withdraws Funds

Makes Deposits

Manages Account

Inquires CustomerActivity

Monitors ATM Status

Replenishes Cash

Upload CustomerTransaction Data

Customer Interface

Customer Activity Inquiry Interface

ATM Status Monitor Interface

Cash Replenishment

Interface

Customer Accounts System

Interface

Use Case Diagram with InterfacesEx.2: 1 Interface for 1 Actor’s Interaction with all UC’s

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ATM System

Customer

Bank Manager

ATM Service Rep

Customer Accounts System

Withdraws Funds

Makes Deposits

Manages Account

Inquires CustomerActivity

Monitors ATM Status

Replenishes Cash

Upload CustomerTransaction Data

Withdrawal Interface

Deposit Interface

Account Management

Interface

Customer Activity Inquiry Interface

Cash Replenishment

Interface

Customer Accounts System

Interface

ATM Monitoring Interface

Use Case Diagram with InterfacesEx.3: 1 Interface for any Actor Interaction with 1 UC

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If the actor is a user: The interface specification describes how the

user interacts with the system – i.e., the “user interface” (UI) – the “human-computer interaction” (HCI)

If the actor is an external system: The interface specification describes how the

system interacts with that external system actor – i.e., the “application program interface” (API)

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ATM System

Customer

Bank Manager

ATM Service Rep

Customer Accounts System

Withdraws Funds

Makes Deposits

Manages Account

Inquires CustomerActivity

Monitors ATMStatus

Replenishes Cash

Upload CustomerTransaction

Data

WithdrawalInterface

Deposit Interface

AccountManagement

Interface

Customer ActivityInquiry Interface

ATM StatusMonitor Interface

CashReplenishment

Interface

CustomerAccounts System

Interface

First Step: Identify All InterfacesUser Interfaces (UI) and System or

Application Program Interfaces (API)

UI

UI

UI

UI

UI

UI

API

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Next: List all Interfaces

Interface Name Actor Type

Funds Withdrawal User UI

Funds Deposit User UI

Account Management User UI

Customer Activity Inquiry User UI

ATM Status Monitor User UI

Cash Replenishment User UI

Customer Accounts System System API

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Each Interface Needs to Have:• A name (e.g., Customer Interface)• A type (e.g., UI, API)• A set of “operation signatures” (for UI and API)

indicating:– which data to “get” from the actor with the operation

(i.e., Get UserId, Name, etc.)– Which data to “return” to the actor when the operation

is complete

• A “storyboard” (for UI only): visual illustration of the sequence of screen designs to complete these operations

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Example of Operation Signatures: Funds Withdrawal Interface

• Get data from card magnetic tapeGet pass code from customer

• Get customer transaction selection(user selects withdrawal)

• Get account type for withdrawal• Get amount to withdraw• Return cash and confirmation message• Return new balance after withdrawal, or• Return error message to customer• Return thank you message to customer

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A User Interface Involves:

• Inputs (Get) into the system by the user, e.g.: Data entry into the system Query information from the system Voice command or input , etc.

• Outputs (Return) from the system to the user, e.g.: A result display A printed output Voice or sound output

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Diagramming the Interface: with “Storyboards”

• User interfaces can be diagrammed as “storyboards”

• A storyboard is a series of drawings that depict how the system looks at the start of the operation and after each significant change to the look of the interface

• Is like a sequence of screenshots that follows the use case execution sequence

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Organization of a Storyboard

Storyboard Sequence

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A Bad Interface Storyboard

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Ergonomics

“Ergonomics (or human factors) is the scientific discipline concerned with the understanding of the interactions among humans and other elements of a system”

Disciplines: physical, cognitive and organizational ergonomics

International Ergonomics Association

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Usability

Derives from the industrial engineering field of “Ergonomics” – how to design things so they are easy to use.

It refers to the “quality of a user's experience when interacting with a product or system … and how well users can learn and use a product to achieve their goals and how satisfied they are with that process ... people who use the product can do so quickly and easily to accomplish their tasks” – usability.gov

Other references: http://www.usernomics.com/usability.html

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User Interface Design

Also referred to as “Human Computer Interaction” (HCI) – is what the usability specialists do to build systems that are easy to use.

HCI also derives from the field of “Ergonomics”, which is now being called “Human Factors” which incorporate cognitive ergonomics and interaction with digital/virtual systems (not just physical).

Other references:

Cornell: http://ergo.human.cornell.edu/ahtutorials/interface.html

Virginia Tech: http://www.edtech.vt.edu/edtech/id/interface/

Carnegie Mellon: http://www.usernomics.com/user-interface-design.html

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Application Program Interface (API)

• Is a specification that describes how other systems or applications can interact with a system

• For example, if you wish to develop Windows or iPhone applications, you need to learn the Windows or iPhone API

• In a use case model an external system actor’s interaction with our system requires an API

• If our system will interact with an external system (arrow pointing out), we need to know the external system’s API

• If the external system will interact with our system (arrow pointing in), the external system programmers need to know our system’s API

Google Earth API

Google Maps API

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In Sum: What to Include in an Interface Analysis Specification:

• A list of all the interfaces between actors and use cases

• For each interface (any actor – user or external system):– Indicate whether the actor is a user (human actor) or an external

system– Prepare a list of operation signatures detailing all the data that is

passed to/from the system before each operation and the data that is returned from/to the system after each operation

• For users (human actors only):– Indicate when/if operations are taking place for data input, display

outputs or printed outputs– Prepare a storyboard for all screen input/output displays and printouts– Analysis of the visual UI for all screen input/output displays and printouts

• For external system actors (only):– Indicate when/if operations are taking place to input or output data

from/to the system– Analysis of the system API

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General Quality Attributes of a User Interface Design

Ease of use Intuitive use and navigation Consistency across screens Simplicity – e.g., no clutter, no information

overload, no busy graphics Exit/cancel options for users Forgiving Businesslike appearance Readable and good color contrast