Versions are evil

Leviticus 0xFEFF Just after something about shellfish

http://api.equestria.magic/v1/

COOL URIS DON’T CHANGE

Uniform

Resource

Identifier

http://v1.api.equestria.magic/

URIS ARE OPAQUEIt’s dark in the smuog

http://not-so-opengraph.api.equestria.magic/

> GET /rainbow-dash > Host: api.equestria.magic > Accept: application/vnd.equestria.ponies.v1+xml

< 200 OK < Content-Type: application/vnd.equestria.ponies.v1+xml < ..

“We encourage resource ownersto only use true content negotiation (without redirects) when the only difference between formats is mechanical in nature.”

Roy Fielding

A conversation I could have had

“User: I need the gravatar of /user/rainbow-dash - Me: it’s only in the v2 format

- User: But there’s no @accept on <img>! - Me: No kidding.”

WHY ARE WE THERE?

“In the world of Web services, there is a strong argument that contracts should be stored and transmitted in a machine-readable format.”

A guy called Don

Frozen in time?

Evolution

BACKWARD COMPATIBILITY

“A product or technology is backward […] compatible if it can work with input generated by an older product”

The source of all truths Wikipedia

FORWARD COMPATIBILITY

“A forward compatible design can accept data from a future version of itself and pick out the "known" part of the data”

42 Wikipedia

XML Schemas

<xsd:any> <xsd:anyAttribute>

JSON

“No one has been stupid enough yet to create a JSON schema language”

Delusional person in the street

Ignore the unknown

• Degrading when possible • Ignore what is not understood.monkey-dash { coolness: 100%; }

Fallback rules

<input type=“monkey” />

DON’T VALIDATE SCHEMAS

REALLY, DON’T.

Style, or substance

<user> <address> Somewhere over the rainbow. </address> <monkey-business enabled=“true” /> </user>

Noise

Datum

DATUMS DON’T KILL PEOPLE, SCHEMAS KILL PEOPLE.

Those pesky schemas. Tsk tsk.