Computed attributes

A computed attribute derives its value from other data in your application. When you define a computed attribute, you can configure it to pull values from other attributes on the same case or related cases, perform calculations on those values, extract values from multivalue attributes, or calculate values from datasets, among other options.

Computed attributes can either be calculated in real-time or cached:

• Using real-time computed attributes ensures the values are always up-to-date, but can slow down your application's performance.
• Using cached computed attributes returns the values faster, but can result in values becoming out-of-date.

As an alternative, you can also use mappings to populate attribute values automatically. For a comparison of the options and the use cases that they are suited to, see Populate case details automatically.

Note:

It is not possible to change whether an attribute is computed or not after the attribute has been created.

Computed attribute template

To define how the value of a computed attribute is determined, use an inline template. For example:

• To fetch the value from another attribute on the current case, type case. and then select an attribute from the current casetype.
• To fetch the value from a metadata field on the current case, type casemeta. and then select a metadata field.
• To fetch the value from an attribute on a related case, first type case. and select the attribute on the current case that contains the case ID of the related case. Then, click the blue text containing the attribute name and use the Link list in the dialog to select an attribute (or metadata field) on the related case. If you select an attribute that contains a case ID, you can create a link to another case and repeat the process. The computed attribute is populated with the value of the final attribute or metadata field in the chain.
• To compare the values in two multivalue fields and either return or remove the values that are common to both, type multivalue. and select Intersection or Difference as appropriate. Then, click the blue text and use case. to identify the two multivalue attributes you want to compare.
  To select a multivalue attribute on a different casetype, select the attribute containing a case ID that identifies the case, and then create a link to identify the multivalue attribute on that case, as described above.
• To fetch the total number of items in a dataset or the result of a calculation on a dataset column containing numeric data, type dataset. and select the aggregation type. Then, click the blue text and use the options in the dialog to select the dataset and column if required.
  If the dataset includes a current case filter, select the attribute that contains the case ID you want to filter the dataset by from the Dataset case pointer list.
• To calculate the number of days until or after a date in an attribute on the current case or a related case, type date. and select Date difference. Then, click the blue text and use the options to select the case attribute or metadata field containing the date you want to calculate the difference from.
• To perform calculations on numerical data stored in case attributes, type math. and select the operation you want to perform. Then, click the blue text and use the options to select the case attributes containing the values you want to use in the operation.

Tip:

The data type of the value returned by the inline template must match the data type of the computed attribute. For a full list of the options available to use in inline templates, see Standard template functions. Note that not all options are suitable for calculating attribute values.

Cached computed attributes

By default, the value of a computed attribute is calculated each time the value is read. For example, if the attribute value is displayed in a view, the value is calculated each time the view is loaded. Similarly, if the attribute value is used in conditional logic on an activity or form, the value is calculated each time the relevant activity stage is reached or the form is loaded.

Calculating the value of a computed attribute in real time can slow down the performance of your application, particularly as the number of cases in your Production environment grows. For this reason, we recommend caching computed attributes where possible.

When Cached is enabled for a computed attribute, the result of the calculation is stored in the same way as normal attribute values. This means the computed attribute value can be read faster in order to display it in a view or use it in conditional logic.

Recalculate computed attributes

The value of a cached computed attribute is recalculated automatically each time an activity is performed on the case. For computed attributes that are only based on other attributes from the same case, this means the cached value is always up-to-date (as the value is always recalculated when an activity is performed that could change a source attribute value).

However, if the computed attribute depends on one or more attributes from other cases, the computed attribute value can become out-of-date when the values of those source attributes change. This is because activities on related cases do not automatically recalculate the cached computed attribute.

You can use a Recalculate case process block activity on the case containing the cached computed attribute to recalculate and update the stored value:

• You can trigger the activity automatically from an activity on the case(s) containing source attributes. For more information, see Chain activities together.
• You can make the recalculate activity available for users to perform manually via an activity widget on the casetype view or a grid widget displaying a list of cases. For more information about adding widgets to views, see Configure pages and views.

You can also use Developer Tools to recalculate a specific case or all cases of a particular casetype.

Tip:

Performing any type of activity on the case will recalculate the cached computed values (and the case reference). You do not have to use the Recalculate case activity type.

Order of recalculation

If you have multiple cached computed attributes on a casetype, you can specify the order in which the attribute values are recalculated each time an activity is performed on the case. This is useful if one or more for your computed attributes depends on the value of another computed attribute on the same case. To set the order, enter an integer in the Order field. The computed attribute with the lowest number is recalculated first.