:PROPERTIES:
:ID:       05698e38-65b2-496c-b02b-1db376ae734c
:END:
#+title: Validation vs Sanitization

There are distinct factors that go into deciding whether to [[id:9914d09e-99fe-46a6-95be-676c5b78ed90][validate input]]
(rejecting unwanted data) or to [[id:2ba04972-f498-41c2-970e-a64c7f3f1c3b][sanitize input]] (accept and alter data).

Commonly, data is validated on input, and sanitized when it is displayed:

#+begin_src plantuml :file validation-and-sanitization.svg
  cloud "Input" as input
  component API {
          interface POST
          usecase "Validate input" as validate
          database "Data store" as data
          interface GET
  }
  frame Client {
          usecase "Sanitize and display" as sanitize
          file "Output" as output
  }

  input -> POST
  POST -> validate
  validate -> data
  data -> GET
  GET -> sanitize
  sanitize -> output

#+end_src

#+RESULTS:
[[file:validation-and-sanitization.svg]]

This has the following benefits:
- Input that is accepted correctly matches the types and constraints of its
  domain.
- The client is soley responsible for ensuring that data is displayed correctly
  and securely.