Constraints is an concept discussed in class that helps prevent a person from committing errors by limiting them what they can do with the user interface.  A great example used in class was the constraints on a form to enter the expiration date for a credit card.

Good Example: Typeform

Typeform applies constraints on how a user can fill out a form by limiting the user to answering one question at a time and allowing the user to go back to the previous question.  Typeform prevents users from answering later questions first as well as ensures only the pertinent questions are presented to the user.

Bad Example: Apple Siri

Siri provides an open-ended interface with no constraints to how the user can correspond with the voice assistant.  If the user presents a prompt that Siri does not understand, it responds with “Sorry, I didn’t understand what you said.” but gives the user no indication on how to correct his input.  The lack of constraints make the interface frustrating for users when they discover a functionality they were expecting to be missing and don’t understand how to correct their behavior to properly interact with the system.

Amendments to Bad Example:

While it is difficult to constrain open speech input systems like Siri, the software can be improved by providing better indicators to guide/constrain the user’s speech choices.  By providing examples of how to interact with the system, users get a better sense of the functionality of the system and will limit their inputs to those similar to the examples provided.  Users are also provided with the option to learn more about what else Siri can do if they feel intimidated by the open-ended interface at first.