five universal principles of api design

Five Universal Principles of API Design

Ronnie Mitra

DevOps: API Management and Application Development

CA Technologies

Director of API Design

DO3T26T

@mitraman

#CAWorld

[…] there is nothing made by human beings that does not involve a design decision somewhere.Bill

Moggridge

Why do we want better APIs?

Expose More Capabilities

Develop Better Applications Faster

Acquire More Developers & Users

Universal Principles of DesignRockport Publishers Inc.

2007

Authors:

William Lidwell

Kritina Holden

Jill Butler

80/20 Rule

Accessibility

Advance Organizer

Aesthetic-Usability Effect

Affordance

Alignment

Anthropomorphic Form

Archetypes

Area Alignment

Attractiveness Bias

Baby-Face Bias

Biophilia Effect

Cathedral Effect

Chunking

Classical Conditioning

Closure

Cognitive Dissonance

Color

Common Fate

Comparison

Confirmation

Consistency

Constancy

Constraint

Contour Bias

Control

Convergence

Cost-Benefit

Defensible Space

Depth of Processing

Design by Committee

Desire Line

Development Cycle

Entry Point

Errors

Expectation Effect

Exposure Effect

Face-ism Ratio

Factor of Safety

Feedback Loop

Fibonacci Sequence

Figure-Ground Relationship

Fitts’ Law

Five Hat Racks

Flexibility-Usability Tradeoff

Forgiveness

Form Follows Function

Framing

Freeze-Flight-Fight-Forfeit

Garbage In-Garbage Out

Golden Ratio

Good Continuation

Gutenberg Diagram

Hick’s Law

Hierarchy

Hierarchy of Needs

Highlighting

Horror Vacui

Hunter-Nurturer Fixations

Iconic Representation

Immersion

Inattentional Blindness

Interference Effects

Inverted Pyramid

Iteration

Law of Pragnanz

Layering

Legibility

Life Cycle

Mapping

Mental Model

Mimicry

Mnemonic Device

Modularity

Most Advanced Yet-

Acceptable

Most Average Facial-

Appearance Effect

Normal Distribution

Not Invented Here

Nudge

Ockham’s Razor

Operant Conditioning

Orientation Sensitivity

Performance Load

Performance Versus Preference

Personas

Picture Superiority Effect

Priming

Progressive Disclosure

Propositional Density

Prospect-Refuge

Prototyping

Proximity

Readability

Recognition Over Recall

Red Effect

Redundancy

Rosetta Stone

Rule of Thirds

Satisficing

Savanna Preference

Scaling Fallacy

Scarcity

Self-Similarity

Serial Position Effects

Shaping

Signal-to-Noise Ratio

Similarity

Stickiness

Storytelling

Structural Forms

Symmetry

Threat Detection

Three-Dimensional Projection

Top-Down Lighting Bias

Uncanny Valley

Uncertainty Principle

Uniform Connectedness

Veblen Effect

Visibility

Visuospatial Resonance

Von Restorff Effect

Wabi-Sabi

Waist-to-Hip Ratio

Wayfinding

Weakest Link

80/20 Rule

Accessibility

Advance Organizer


Affordance

Alignment


Archetypes

Area Alignment

Attractiveness Bias

Baby-Face Bias

Biophilia Effect

Cathedral Effect

Chunking


Closure


Color

Common Fate

Comparison

Confirmation

Consistency

Constancy

Constraint

Contour Bias

Control

Convergence

Cost-Benefit

Defensible Space

Depth of Processing

Design by Committee

Desire Line

Development Cycle

Entry Point

Errors

Expectation Effect

Exposure Effect

Face-ism Ratio

Factor of Safety

Feedback Loop

Fibonacci Sequence


Fitts’ Law

Five Hat Racks


Framing



Golden Ratio

Good Continuation

Gutenberg Diagram

Hick’s Law

Hierarchy

Hierarchy of Needs

Highlighting

Horror Vacui





Inverted Pyramid

Law of Pragnanz

Layering

Legibility

Life Cycle

Mapping

Mental Model

Mimicry

Mnemonic Device

Modularity

Most Advanced Yet

Acceptable


Appearance Effect

Normal Distribution

Not Invented Here

Nudge

Ockham’s Razor



Performance Load


Personas


Priming



Prospect-Refuge

Prototyping

Proximity

Readability


Red Effect

Redundancy

Rosetta Stone

Rule of Thirds

Savanna Preference

Scaling Fallacy

Scarcity

Self-Similarity


Shaping

ignal-to-Noise Ratio

Similarity

Stickiness

Storytelling

Structural Forms

Symmetry

Threat Detection



Uncanny Valley



Veblen Effect

Visibility


Von Restorff Effect

Wabi-Sabi

Waist-to-Hip Ratio

Wayfinding

Weakest Link


Forgiveness

Immersion

Satisficing

Iteration

1. Flexibility-Usability Tradeoff

Flexibility

“How many problems will this help me solve?”

“How many ways can I use this?”

“How much stuff can this thing do?”

Usability

“How easily can I accomplish my goals?”

“How difficult is it too get started?”

“What do I need to know?”

adding functionality increases

complexity

Low Complexity

Minimum Capabilities

Maximum Capabilities

adding functionality increases

complexity

High Complexity

added complexity can increase confusion

!!!

Low Complexity

High Complexity

An API designed for applications

GET /account

GET /customer

GET /transfers

POST /transfer

An API designed for an application

dashboard

GET /dashboardMetrics

Flexibility is valuable when we are uncertain

about future user needs

Flexibility is valuable when we are uncertain

about future user needs

Data Chunking

Querying

Order of Calls

Endpoint Location

Data Model

Capabilities

APIClient

UsabilityAid

Flexible System

AndroidJavaSDK

HTTP Based API

This is not a binary tradeoff

Flexibility Usability

Every design decision places you on the spectrum

MaximumFlexibility

MaximumUsability

2. Forgiveness

Forgiveness

Help users recover from mistakes

Help users avoid making mistakes

Warn users of danger ahead

APIClient

Oh Larry…. I forgive you.

`

I’ve made a horrible mistake!

APIClient

Application Developer

Application User

Encourage exploration and learning by providing safe places


Client API

!

Encourage exploration and learning by providing safe places


Client API sandbox

Provide reversibility in the API

Client

Application UserUNDO

UNDO

Provide reversibility in the API

Application User

APIClient POST /undo

3. Immersion

The best moments usually occur when a person’s body or mind is stretched to its limits in a voluntary effort to accomplish something difficult and worthwhile

MihalyCsikszentmihalyi


Client API

4. Iteration

An Iterative API Design Approach

1 Determine Goals

2 Identify Users

3 Design Interface

4 Evaluate

5 Implement

Why?

1 Determine Goals

2 Identify Users

3 Design Interface

4 Evaluate

5 Implement

revenue reach innovation

growth compliance intel

platform

language

organization

distance

knowledge

risk profile

investment

1 Determine Goals

2 Identify Users

3 Design Interface

4 Evaluate

5 Implement

For Whom?

Expertise

Goals

Familiarity

Ideate, Experiment, Sketch & Prototype

1 Determine Goals

2 Identify Users

3 Design Interface

4 Evaluate

5 Implement

Test Assumptions

1 Determine Goals

2 Identify Users

3 Design Interface

4 Evaluate

5 Implement Lab Evaluation

Peer Evaluation

User Observation

Write Client Code

Participatory Design

Design Doesn’t Stop

1 Determine Goals

2 Identify Users

3 Design Interface

4 Evaluate

5 Implement

Analyze Real Usage

Identify Usability Bugs

Improve Functionality

Iterate and Evolve

Iterations will improve design

API implementations are difficult to change

Try to iterate before implementation

5. Satisficing

Herbert A. Simon

Searching for the best can only dissipate scarce cognitive resources; the best is the enemy of the good.

“

”

“The best design decision is not always the

optimal design decision.”

Scale

Revenue

Competition

-£ £ £

5. Satisficing

4. Iteration

3. Immersion

2. Forgiveness

1. Flexibility-Usability Tradeoff

80/20 Rule

Accessibility

Advance Organizer


Affordance

Alignment


Archetypes

Area Alignment

Attractiveness Bias

Baby-Face Bias

Biophilia Effect

Cathedral Effect

Chunking


Closure


Color

Common Fate

Comparison

Confirmation

Consistency

Constancy

Constraint

Contour Bias

Control

Convergence

Cost-Benefit

Defensible Space

Depth of Processing

Design by Committee

Desire Line

Development Cycle

Entry Point

Errors

Expectation Effect

Exposure Effect

Face-ism Ratio

Factor of Safety

Feedback Loop

Fibonacci Sequence


Fitts’ Law

Five Hat Racks


Forgiveness


Framing



Golden Ratio

Good Continuation

Gutenberg Diagram

Hick’s Law

Hierarchy

Hierarchy of Needs

Highlighting

Horror Vacui



Immersion



Inverted Pyramid

Iteration

Law of Pragnanz

Layering

Legibility

Life Cycle

Mapping

Mental Model

Mimicry

Mnemonic Device

Modularity

Most Advanced Yet-

Acceptable


Appearance Effect

Normal Distribution

Not Invented Here

Nudge

Ockham’s Razor



Performance Load


Personas


Priming



Prospect-Refuge

Prototyping

Proximity

Readability


Red Effect

Redundancy

Rosetta Stone

Rule of Thirds

Satisficing

Savanna Preference

Scaling Fallacy

Scarcity

Self-Similarity


Shaping

Signal-to-Noise Ratio

Similarity

Stickiness

Storytelling

Structural Forms

Symmetry

Threat Detection



Uncanny Valley



Veblen Effect

Visibility


Von Restorff Effect

Wabi-Sabi

Waist-to-Hip Ratio

Wayfinding

Weakest Link


Recommended Sessions

SESSION # TITLE DATE/TIME

DO3T25TTech Talk: Hypermedia-Driven Orchestration

in Microservices11/18/2015 at 2:00 pm

DO3X96S

Tech Primer: Implementing Adaptable

Microservices; A Methodology for Loosely-

Coupled Components

11/18/2015 at 3:00 pm

DO3X95S

Tech Primer: Accelerating the Mobile App

Development Process – How to Simplify

Building Context Aware and Reactive Mobile

Apps

11/18/2015 at 4:30 pm


Must See Demos

Unlock the Value of APIs

API Developer Portal

Theater 3

Simplify API Design & Creation

Live API Creator

Theater 3

Accelerate Mobile/IoTDevelopment

Mobile App Services

Theater 3

Extend Existing Architectures

API Gateway

Theater 3


For More Information

To learn more, please visit:

http://cainc.to/Nv2VOe

CA World ’15

http://cainc.to/Nv2VOe

http://bit.ly/1wbjjqX

five universal principles of api design

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