Pattern 78: Pipeline interaction
AKA:

You are trying to give a SENSE OF PROGRESS (48) and are aware of the phenomenon of BUTTON GRAVITY (77).

Sometimes a process-driven interaction can constrain user choices and behaviour (‘constrain’ because pipeline interaction may never be the ideal solution). Business procedures demand that information is displayed or captured in a certain order. This order may not suit the user or confirm to his mental model of the domain.

Therefore

Provide a series of linked pages that the user must visit in strict sequence. Use SENSE OF PROGRESS (48) to ensure that commitment points are made plain.

Allow users to revisit previous pages and correct them. Cache information entered in case of line failure. Don’t force people to enter stuff that isn’t essential (e.g. their fax numbers) or in fixed categories (e.g. UK instead of Wales, etc.)

This pattern is terminal within this language.

Contributors and sources
Paul Dyson, Dave Sissons

As Hegel put it, freedom is the recognition of necessity. Users should be free to do things their way unless they are engaed in a dialogue with your business processes that might hard on e of the parties if they fail to follow the necessary steps. They will ultimately feel less free when their transaction fails and the wrong goods arrive.

Examples
Insurance quotations (Royal and Sun Alliance). The site was written on top of an existing system, so the developers were constrained by the way that system worked. For example, they needed to identify who the customer was and the car that they would be driving before taking details of who else would be driving it. They were therefore forced to ask for information in a certain order.

The shopping basket at lastminute.com provides another typical solution.

Browse the language	What is Wu?	Look at an example pattern sequence	Structure of the patterns
Comment on Wu	Contributors	Return to TriReme home page	Links to related sites