Mike Amundsen

@mamund

“You can't cross the sea merely by standing and staring at

the water.”

- Rabindranath Tagore

Mike Amundsen

Presenter, Architect, Programmer

Current focus: “Hypermedia”

New book coming…

Designing Hypermedia APIs

w/ HTML5 and NodeJS

– O’Reilly, late 2011

Goals

Identify common Web implementation

patterns

Encourage you to re-think your habits

Challenge existing frameworks & tooling

Improve the quality of information on the

Web

Non-Goals

Explain the HTTP Protocol

Defend the REST Style

Promote/Denigrate any

Platform/OS

Programming Language

Web Library or Framework

My Hidden Agenda

When I get done,

I hope there will be…

Less of this…

More of this…

“Vision without action is a daydream. Action without vision

is a nightmare.”

– Japanese Proverb

ROT

Representational

Object

Transfer

Representational

Object

Transfer

Object

“In computer science, an object is any

entity that can be manipulated by the

commands of a programming language,

such as a value, variable, function, or data

structure.”

- Wikipedia

Why is this bad?

It’s a Web “anti-pattern”

Wait, it’s a what?

Anti-pattern

“In software engineering, an anti-

pattern (or antipattern) is a pattern that

may be commonly used but is ineffective

and/or counterproductive in practice.”

- Wikipedia

Anti-pattern

“In software engineering, an anti-

pattern (or antipattern) is a pattern that

may be commonly used but is ineffective

and/or counterproductive in practice.”

- Wikipedia

On the Web, ROT

is ineffective

and/or

counterproductive

Object Serialization

Type Marshaling

Type Marshaling Problems

Updates on the server can break the

clients

Objects/Members added/changed/removed

Moving to a new server/domain can

break the clients

Object IDs (URIs) added/change/removed

Modifying the process flow can break

the clients

Object processing added/changed/removed

On the Web,

ROT doesn’t scale

This is NOT an HTTP Problem

This is the nature of

distributed networks

Some examples please….

Schema Publishing ROT

Type Hints in the Payload ROT

URI Construction ROT

Object-Based Media Types ROT

They all suffer from

the same shortcoming

They try to solve

the wrong problem

"How can a server

successfully export it's private

objects in a way that

clients can see and use

them?"

Not the correct question…

"How can

a server and client share a

common understanding of

the payloads passed between

them?"

Much better question…

We need to

Stop sharing private objects

Look beyond local “types” as sharing units

Make it work across:

Platforms

Languages

Frameworks

We need a

common understanding

“Freedom lies in being bold.”

- Robert Frost

REST

Representational

State

Transfer

Representational

State

Transfer

State

“In computer science and automata theory,

a state is a unique configuration of

information in a program or machine.”

- Wikipedia

“State” is not an object.

The “Type-less” Web

The Web has no local “types”

The Web doesn’t need any.

The Web has payloads

Message

Metadata

We share the “state” of an app,

not the objects on the server.

Ok, how do we share “state”?

We pass messages…

That’s it?

Well…

Not just “any” messages…

We share “state” on the Web

using a “media type”

Media Types

text/html, application/xml, application/json, etc

Elements, attributes, properties, arrays, etc.

Structured, well-formed, valid, etc.

Independent of

Platform

Language

Framework

Actually, there is a

special group of media types

that are “best” for the Web…

Hyper-media Types.

Hypermedia Types

Not just “what”

name, email, price, size, …

Also “how”

a, link, img, form, input, …

Hypermedia messages

contain H-Factors

H-Factors

Servers include these to tell clients what

they can do next…

Link Factors

Control Factors

Link Factors

LE = Link Embedding

HTML.IMG

LO = Link Outbound

HTML.A

LT = Link Template

HTML.FORM[action=“get”]

LN = Link Non-Idempotent

HTML.FORM[action=“post”]

LI = Link Idempotent

HTML.FORM[action=“put”]

Control Factors

CR = Control Reads

HTML.LINK[rel=“stylesheet”]

CU = Control Updates

HTML.FORM[enctype=“text/plain”]

CM = Control Methods

HTML.FORM[method=“post”]

CL = Control Links

A[rel=“payment”]

On the Web,

we share understanding

using media-types.

What do we understand?

What do we understand?

What do we understand?

What do we understand?

So we must design

the messages we share…

Design and Share Messages

Where is the data?

Where are the links?

How can I send queries?

How can I modify data?

And we must document the

design…

And create servers that

understand the media type…

And write clients that

understand the media type…

That’s how the Web is meant

to be played!

“The important thing is not to stop questioning.”

- Albert Einstein

Stop Marshaling Types

Start Using Hypermedia

Start Designing Messages

Give us Less ROT and More REST

Enjoy the Benefits of the Web!

Mike Amundsen

@mamund