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Fundamentals: why state machines?

States. The final frontier. These are the voyages of an enterprising developer. Her eternal mission: to explore strange new techniques, to seek out better ways to engineer for mental models and new design patterns. To boldly go where a few awesome devs have gone before.

So you’ve found our poignant guide to SCXML and surely you’re wondering “Why should I want to go out of my way to use formal state machines?” or something like that. Hopefully this introduction addresses that kind of question.

An example: Nancy’s RPG

The problem

paydro

CREATE ROLE owner LOGIN ENCRYPTED PASSWORD 'secret' CONNECTION LIMIT 3;
ALTER ROLE owner SET statement_timeout = 20000;
ALTER ROLE owner SET lock_timeout = 3000;
ALTER ROLE owner SET idle_in_transaction_session_timeout = 3000; -- v9.6+

CREATE ROLE readwrite_users NOLOGIN;
CREATE ROLE readonly_users NOLOGIN;

CREATE DATABASE exampledb WITH OWNER owner ENCODING UTF8 LC_COLLATE 'en_US.UTF-8' LC_CTYPE 'en_US.UTF-8';