Cross validation messages should be symmetric or asymmetric?

Question

Lets let that there is a form in a popup window which contains the properties that are configurable for a chart and as you go on changing the values for the properties the underlying chart is refreshed so as to give the user a feel of what kind of chart he is configuring . Now there are two properties :

1. Major tick increment
2. Minor tick increment

The invariant that the Chart needs to maintain is major >= minor . So do I need to add different validation messages like :

Major should be greater than or equal to minor

( this one is fired when the user puts an invalid value into major and tries to tab out of that field)

Minor should be lesser than or equal to major

( this one is fired when he puts an invalid value into minor and tries to tab out of that field)

or a single validation message which could be either of the two above ?

Answer 1

I'd go for having a single consistent error message if error messages were the solution.

Some random thoughts on other options:

• You could remove the problem of errors completely by changing "minor tick increment" to "minor ticks per major tick"

• You could remove the problem of errors completely by having the ticks being entered by sliders that do not allow the minor-tick count to be > major-tick count

• You could remove the problem of errors completely by automatically resetting the major-tick/minor-tick counts to match the other if bounds are exceeded.

• You could just not worry about the constraint and display the dodgy major/minor tick counts on the graph. The user will see this in the preview and fix it themselves.

Answer 2

What kind of range(s) are we talking about for the two input fields?

If the ranges are not too broad, it may be possible to use sliders as an input mechanism. This may allow you to dynamically enforce an upper and / or lower limit on one slider based on the value of the other, such that users could never have a clashing set of values.

e.g. if the major tick increment slider was set to 10, then the max value for the minor increment slider could be set to 10 to prevent the user from setting a higher value. Conversely, if the major tick increment slider high enough for the minor increment slider to be set to 20 then this could update the min value for the major tick increment slider to 20.

Obviously, this solution may not be practical if the input range were too large to set using a slider control (e.g. 0 to 10,000).