Reference Information › User Interface Reference Guide › Defining Simple Appliances › Defining Properties

Defining Properties

Properties are configuration parameters used to specialize the behavior of an appliance in a specific application role. Properties work in conjunction with interface connections to specialize an individual instance.

You can define all the configuration properties that you want to be modifiable as well as fine-tune parameters, timeouts, file locations, appliance volumes, and mode of operation of the appliance. You should expose property configuration parameters that can be used by the user and cannot be fixed by the class itself.

Note: Dependencies or binding to outside services should be expressed as output terminals, not properties.

Appliances typically contain 3 to 12 properties with most having default values. You should define the most frequently changed values first.

Property Constraints

You can set a value constraint on a property value.

The property constraints are:

• Minimum or Maximum Range - allows a minimum and maximum value for integer properties. To limit only one value on the range, leave the other value empty. For example, limit the minimum value and leave the maximum value blank
• FIlter - allows a regular expression for validating the property value. Regular expressions are very error-prone. Use this caution with this constraint or simply use the values constraint instead. The syntax of the filter is the same as the Perl regular expression pattern matching. The entire property value is validated. For example, it is as if /^filter$/ was used in a Perl statement to check for a match where filter is the value of the filter attribute. You can use the filter constraint with any property type.
• Allowed Values - defines an enumerated set of values, such as yes|no or high|low. The syntax is literal values separated with |. Using the values constraint with the lowercase property attribute removes case sensitivity from the value set.