Consistency across multiple devices
In the case of cross-platform systems, designers also need to consider
consistency across different devices. Consistency works to create a sense of
coherence of the overall system.
Words, data and actions that are the same across devices should be understood
to be the same. Words, data and actions that are different should be understood
to be different. This helps users form a clear mental model of the system and
its capabilities. Knowledge that users have gained about the system from one
device can be transferred to help them learn how to use other devices.
Other elements that may need to be consistent to some degree across devices
include
Aesthetic/visual design (to make the devices look, feel and sound like a
family)
Interaction architecture (how functionality is organized) and
Interaction logic (how tasks are structured or the types of control used).
Guidelines for consistency
Use consistent terminology
As a rule of thumb, the highest priority is to use consistent wording across
devices. This ensures that data and actions across different platforms are
understood to be the same thing. Whatever the display capabilities of each
device, you can always give functions or data the same label even if you can’t
make them look the same.
For example, imagine you are working on a connected heating controller that
offers 3 mode options: ON (heating is on continuously), AUTO (heating is
running to a pre-programmed schedule), and OFF (see e.g. figure 9.21). These
are already set in the fixed segment LCD display and cannot be changed. You
might think that ON and AUTO are not the clearest terms. You’d prefer to
change them to CONTINUOUS and TIMER or SCHEDULE in the
smartphone app interface. However, this would create a disconnect: users then
have to understand that ON and CONTINUOUS are the same thing.