Properties — Concepts and terms

Standard and custom properties

PRPC includes hundreds of standard properties in the Work- and Assign- base classes. For easy identification, the names of standard properties start with px, py, or pz. These are referenced in standard activities, reports, and examples, so it is worthwhile to become familiar with standard properties before deciding to create custom properties.

Saving property values

The process of creating a (persistent, saved) instance involves:

• Creating an empty clipboard page of a concrete class.
• Providing values for some properties in that class, at least enough to form a unique key. This can be done with a data transform or through activities (typically using one of the Property-Set methods).
• Validating property values to ensure that the values meet format, range, or other tests. This may involve comparison with a set of field value keys.
• If valid, saving and committing the object into the database.

Use the Clipboard tool for viewing properties and values on the clipboard. You can create the first instance of a new class through direct clipboard manipulation using the tool to test your class and property definitions. Later, when the class and property definitions are considered, you can define activities, data transforms, and HTML forms to create instances.

Definitions

Formally, a property is a type of rule, an instance of the Rule-Obj-Property rule type. Informally, properties provide labels or addresses for values. Properties may be scalar (consisting of a single text string or a single page) or aggregate (containing multiple, individually named values). Aggregate properties provide facilities similar to arrays, repeating groups, and unordered sets or collections found in other development tools.

A property may have a null value, which for Single Value properties is identical to the empty string, entered as "". To set a property means to provide a value, which may be the null value.

For a persistent object stored in the database, properties correspond to "fields," or, in many situations, to database columns. In the context of the clipboard, the word property refers both to a name (or path) and to its value(s).

Because a property is a rule, it has an associated Applies To class and — with some restrictions — its features and functions can be overridden by other versions or by other properties with the same name.

Every property has one of eleven modes. The three categories of modes are Values, Pages, and Java Objects. Value mode properties have a Type (such as Text, Identifier, DateTime, Integer, Decimal, and so on) that determines what you can do with the value.

In many PRPC forms, developers enter a special notation (similar to Java notation for classes) called dot notation to identify properties or parts of properties. Application users supply values for many scalar property values directly through user input on an HTML form. However, some properties are special, meaning that their value can set only through a computation, not directly through user input.

	About Property rules
	Atlas — Standard Property rules

Concepts

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