Information casualty

An information casualty is an event in which relevant information fails to reach an observer in time to inform perception, action or participation. It is the founding concept of the Tyrer Framework and gives the Zero Information Casualty standard its name.

The term is deliberate. When a blind pedestrian walks into an obstacle because nothing signalled it, that is not a usability issue; it is a failure in the information layer of the environment. When an interface renders a critical control as an unlabelled picture, the person who can't perceive it hasn't been inconvenienced; they have been cut off from what they need to act. Information casualties are not edge cases. They are the predictable output of Tyrer's Law.

Every word works

The ZIC standard reads the definition closely. Reach means the failure can happen anywhere between publisher and reader: in the encoding, at the door, on the wire, or inside the machine that read it. In time means that arrival at prohibitive cost or intolerable delay is a failure of arrival: "A reader forced to labour for information that another reader receives at a glance has not been served equally; she has been served late."

The four classes

ZIC names four places the failure can happen, each with a question:

1. Rendering Casualty: can they read it?
2. Admission Casualty: is the person's reader allowed in?
3. Delivery Casualty: did it actually arrive?
4. Reconstruction Casualty: did it survive being read?

The definition is one; the classes are where it breaks.

Behind the scenes

A real idea, defined in The Tyrer Framework (Part One) by Charli-Jo Tyrer, and divided into four classes in Zero Information Casualty v1.7 (§1.8). This entry summarises them; the documents are the authority.