NOT.1:1 - Problem frame

Use this when you are choosing or designing a notation and cannot yet say what its users must be able to express, recognize or do with an expression. A candidate may name all the right objects while hiding their order, dependence or duration. Another may express the distinction but make a frequent change require rebuilding the whole description.

Start with a piece of work: composing operations, comparing two models, tracing a dependency or performing a sequence are examples. Identify an operation that a person or computational agent needs to carry out using the notation. Then find two cases that this operation must treat differently. Trying to express and use those cases gives the first design requirement that can be acted on.

The reader needs enough knowledge of the practice to explain why the cases differ and what a useful result would be. That knowledge can come from a collaborator. Choosing the notation does not require the designer to perform every specialist inference unaided; it does require access to the distinctions that those inferences use.

The result is a choice of distinctions and operations to support, together with a small expression or interaction that shows how a proposed notation could support them. It may instead be a reason to keep an existing notation, preserve an unresolved choice, or obtain a missing account of the work before adding symbols.

If a suitable notation already exists and only one expression needs repair, construct that expression under its rules using A.6.3.RT.OE. Return here when the rules themselves lack a needed distinction or make the required operation impractical.