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 them. The rules are bi-directional, meaning the order in which parameters are selected does not matter - disallowed combinations of values are always prevented.
Definition of disallowed parameter values
A rule is defined by first selecting the parameters to include, and then selecting the specific values for each parameter that are not allowed to combine. For multi-choice parameters, individual multi-choice values are selected to participate in the rule, rather than the parameter as a whole. Depending on the type of parameters 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. For numerical lookup parameters, the disallowed values can also be defined as ranges, just like for double 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, you can define the allowed set of values instead of the disallowed ones by selecting the Check allowed values option. Consequently, any unselected values become disallowed, and any newly added values will be disallowed by default.
You can also compare the values of two parameters within a disallowed combination rule to create a constraint that requires one parameter to be greater than or equal to the other.
The behavior depends on the number of parameters in the rule
While most disallowed combination rules are defined with two parameters, a rule can contain a single parameter or more than two parameters.
A disallowed combination rule with a single parameter makes the selected values impossible to choose, regardless of the values set for other parameters. This can be used, for example, when introducing new lookup values that should not yet be available for selection, but are required to prepare other parts of the configuration model, such as prices, bills 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 while remaining hidden or disabled in the production site.
A disallowed combination rule with more than two parameters becomes active once it is one step away from being fulfilled. For example, in a rule with three parameters, the user is allowed to select disallowed values for two of the parameters, but the system will block the disallowed value for the third parameter, regardless of the selection order.
Disabling or hiding disallowed values
By default, disallowed values of a lookup parameter are disabled in the end-user interface. This allows users to click on a disallowed value, prompting the system to display which other parameter(s) need to be changed to unlock it.
However, you can also hide disallowed values. This is useful when users should not be informed about options that are unavailable in their region, for example. This behavior can be controlled for both lookup parameters and individual lookup values by selecting the Hide values if disabled or Hide if disabled options, respectively.
The same behavior applies to hiding multi-choice values, although the setting for hiding multi-choice values is only available at the value level. Hiding occurs when Checked is disallowed, not when Unchecked is disallowed.
Automatic unlock to make all values selectable
Sometimes, disabling or hiding disallowed values can make the configuration process cumbersome, as it requires users to change other parameters just to select a value that is currently blocked. A common scenario involves a parameter representing a product model; if different models are part of multiple disallowed combination rules, it can become difficult to change the model later in the configuration process once other parameters have already been selected.
To avoid this, you can enable Automatic unlock for a parameter within a disallowed combination rule. This keeps the disallowed values selectable. Instead of blocking the selection, the rule engine will clear another parameter within the disallowed combination rule upon selection, rendering the conflict ineffective. The parameter to be cleared is determined by the Parameter to clear setting.
When a parameter is cleared in this manner, you can optionally display a message to the user by selecting Show message on unlock. This message displays the Description of the rule and specifies which parameter was cleared.
