Disallowed combination rules define combinations of parameter values that are not allowed. The system prevents users from selecting these values by either disabling or hiding the values. The rules are bi-directional, so it doesn't matter in which order parameters are selected - disallowed combinations of values are always prevented.
Definition of disallowed parameter values
A rule is defined by first selecting which parameters that should be included and then for each parameter selecting the values are not allowed to combine. In the case of multi choice parameters it's the multi choice values that are selected to participate in the rule rather then the actual parameters. Depending on the type of parameters that are included in a rule the disallowed values or ranges of values are defined in different ways:
•Lookup parameter: One or more values are selected from a list. In the case of numerical lookup parameters, the disallowed values can also be defined as ranges in the same way as for double parameters and integer parameters.
•Double parameter, Integer parameter: Disallowed values are defined as ranges of values. A range can be less than or greater than a defined value or the inside or outside range defined by two values.
•Boolean parameter, Multi choice value: The values checked or unchecked can be selected as disallowed.
For lookup parameters it's possible to define the allowed set of values instead of the disallowed values. This is done by selecting the option Check allowed values. Then those values that are not selected are the disallowed values and new values that are added to the parameter become disallowed by default.
From version 3.3.1 it's possible to compare two parameter's values in a disallowed combination rule and create a constraint that requires one of the parameters to be either greater or equal to the other parameter.
The behavior depends on the number of parameters in the rule
Even if most disallowed combination rules are defined with two parameters, it's possible to have a rule with a single parameter or a rule with more than two parameters.
A disallowed combination rule with a single parameter will make the selected values as impossible to select no matter what values that are set for other parameters. This can, for example, be used when introducing new lookup values that should not yet be possible to select but are needed for the preparation of other parts of the configuration model like prices, bill of materials or visualizations. By also setting the site effectivity for the rule the new lookup values can be made available for testing in the administration site meanwhile being hidden or disabled in the production site.
A disallowed combination rule with more than two parameters becomes active once it's one step from being fulfilled. So, for a rule with three parameters, it's allowed for the user to select disallowed values for two of the parameters but not for the third, no matter in which order the selection is done.
Disabling or hiding disallowed values
By default, disallowed values of a lookup parameter get disabled in the end user interface. This way the user can click on a disallowed value and the system will tell which other parameter(s) that need to be changed in order to unlock the value.
However, it's also possible to hide disallowed values, which is useful when the user shall not be informed about options that e.g. are not available in the user's region. This behavior can be controlled for both lookup parameters and individual lookup values by selection of the options Hide values if disabled or Hide if disabled respectively.
The same behavior applies for hiding multi choice values, though the setting for hiding multi choice values is only found at the value level and hiding occurs when Checked is disallowed, not when Unchecked is disallowed.
Automatic unlock to make all values selectable
Sometimes disabling or hiding disallowed values makes it cumbersome for the user since it requires changes of other parameter's values to select a value that is blocked by rules. A common scenario is that a product has one parameter that represents its model and that different models are part of many disallowed combination rules which in turn make it hard to change the model further down in the configuration process once other parameters have been selected.
To avoid this Automatic unlock can be selected for a parameter in a disallowed combination rule. This will make the disallowed values selectable and instead the rule engine will on selection clear out another parameter that is part of the disallowed combination rule and thereby render it ineffective. Which parameter to clear it is controlled by the selection Parameter to clear.
When a parameter is cleared out in this way a message can optionally be shown to the user by selecting Show message on unlock. The message will show the Description of the rule and the parameter that gets cleared out.
