Agreements Between Programs

A protocol is a promise about shape and order: what one program sends, what the other answers, and what happens when either side is wrong. HTTP carries most of the web; REST is a style of using it around named resources; SOAP wraps each message in an XML envelope with a contract (WSDL) that tools can check before anything runs. Most integration work is noticing where a record changes shape on the way through, and making a failure say where it happened.

#>protocols_essentials

Protocols Essentials

Requests and responses

Methods, status codes, headers: the vocabulary every web integration shares.

mdn: HTTP overview

HTTP semantics

The current standard for what GET, PUT, and a 409 are supposed to mean.

rfc 9110

Resources, not calls

Where REST comes from: a constrained style that lets caches and intermediaries help.

fielding: REST

Envelopes and contracts

SOAP messages, faults, and why enterprises still rely on a checked contract.

w3c: SOAP 1.2 primer