Graphics
When editing graphic data, allow users to change display
attributes by whatever means were used to select those attributes in the first
place.
Example: If line type is selected
initially from a menu of displayed attributes, then changing a line type should
also be accomplished via menu selection.
Comment: Many editing changes will be made during data entry, rather
than as separate later actions, and thus it is important that entry and editing actions be consistent.
Provide easy means for saving and retrieving graphic displays or
their component elements at different stages in their creation.
Comment: A user
should not have to create a graphic image more than once. Once a graphic element
has been created, a user should be able to save it for possible re-use.
Comment: As a protective measure, a user might wish to save different
versions of a graphic display at successive stages during its creation, in order to return to an earlier state if later results seem unsatisfactory. During creation, the elements added to a graphic display can be interrelated in complex ways, and thus stepwise deletion of unwanted elements could prove a difficult process. An UNDO command might be helpful for deleting some of the most recently added elements. But storage and subsequent retrieval of interim
versions of the display may be more helpful for a foresighted user.
Allow users to name graphic displays or designated elements, in
order to aid storage and retrieval or manipulation during graphic data
entry/editing; and provide means for a user to review a current "catalog" of
named elements.
Comment: Standard displays and graphic components
might be assigned names utomatically by the computer, but users will still need
a capability to assign their own names to interim versions of displays in
creation, or to various elements of those displays. In either case, users may
forget what names have been assigned; some "catalog" of currently named elements
will serve as a helpful reminder.
Comment: For currently displayed material, pointing may be more convenient
than naming for the designation of selected elements; but names will certainly aid the retrieval of stored material.
Provide automatic registration or alignment of
computer-generated graphic data, so that variable data are shown properly with
respect to fixed background or map data at any display scale.
Comment: When
users are required to enter data via some separate device such as a graphics
tablet, rather than directly on the display surface, it may be necessary for a
user to participate in some computer-prompted procedure for ensuring data registration. Such a procedure may prove error-prone,
however, and should be considered an undesirable expedient.
When graphic data must be entered in an organized hierarchic
structure, in different sections and at different levels of increasing detail,
provide computer aids for that purpose.
Example: For entering map data, a user might have to specify different
levels of data storage for a city's name and location, its municipal boundaries, its major road patterns, its street names and house numbers, etc.; computer aids could help that process.
See also:
When graphic data represent relations among real objects, provide
appropriate computer logic based on models of physical probability to validate
data entries.
Example: If data indicate
that a military land unit has been reported in the middle of a lake, the
computer should call that discrepancy to the user's attention.
Comment: If inconsistencies of data entry cannot be resolved immediately,
the computer might keep track of unresolved questions pending receipt of further data.
See also:
Consistent Method for Attribute Selection
