When a user enters a value in a
form, related values can also change. Declarative processing allows you to
easily configure your application so that the system can automatically update
property values such as an order amount.
Declarative Processing
Declarative
processing
identifies and maintains computational relationships among properties.
The primary benefit of declarative
processing is that updates occur only when triggered in the application.
The system monitors the application
to determine when a trigger event occurs.
Declarative rules define a trigger
event and
resulting action.
For example, when input values
change, the declarative process automatically updates related property values.
Declarative Processing
Expression
Constraint
Data
Page
OnChange
Trigger
Index
Procedural Processing
Procedural
processing depends
upon rules — such as data transforms, activities, or user interface (UI) rules
— to instruct the application when to look for a trigger event.
Updates are not automatic. When a
user enters values, nothing changes until the user submits the form.
The submit process must trigger the
data transform to perform the update. To make the changes visible to users as
they enter values, you must configure sections to use the data transform to
refresh the fields.
Procedural Processing Maintenance
An Enter Order form uses a data
transform to calculate the total order amount based on the item price and order
quantity.
Add a Review Order form to your
application, and reuse the fields for calculating the total order amount.
If you do not add the same data
transform to the Review Order form, the total order amount is not updated when
the user changes the order quantity from 2 to 3.
Declare Expressions
Declare expressions use source
property values to calculate and immediately update a property value.
The property value updates after a
trigger event occurs, such as when a user updates the quantity of an order.
Declarative Networks
A declarative network is a set of
interdependent declare expressions.
For a list of declarative networks
in an application, select Designer Studio > Process &
Rules > Business Rules.
A declare expression can use the
target property from another declare expression as a source property.
For
example, an Order Total field displays the total value on a purchase order form.
This
field uses a declare expression to calculate its target property — the order
total — as the sum of the item totals.
The
item total is a target value for another expression that multiplies the
quantity and the unit price.
Forward Chaining
Expressions either push updates to
the target property or pull values from the source properties.
Forward chaining in a declare
expression pushes updates to the target value.
A declare expression uses two
source properties, item cost (USD400) and quantity, to calculate the target
property — item total.
The user increases the number of
chairs from 5 to 6. When the user changes the quantity, the expression
recalculates the item total.
Forward chaining is the default
declare expressions setting.
Backward Chaining
Backward chaining pulls values from
the source property or properties.
The target property value does
not automatically
update when a source property changes.
An expression using backward
chaining only updates its target property when the application references the
property by name.
When the target property is
referenced, the expression references the source property or properties to
update its target.
Backward Chaining Options
Chaining and Performance
Consider where the source property
is referenced and how the target property is referenced when selecting a
chaining method.
Forward chaining can slow system
performance if an expression uses many source properties that change
frequently.
The impact to performance might
affect response time.
If you display a property at the
end of a process — such as the grand total of an order — backward chaining may
avoid unnecessary updates and improve response time.
How to Set a Property Value with a
Declare Expression
Define a property value with a
declare expression steps:
1.Identify
the target property when you create the declare expression.
2.Identify
the source properties when you define the expression.
3.Specify
the chaining direction.
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