Using Pseudo-attributes for Accessing Data

(This section reiterates and expands the concept of extracting design parameter settings for use in template property rules.)

Design Datasets (DDSE) are used to store the properties of design template items, which may then be used to define the template’s parameters. Each property is stored in a Design Data (DDAT) element under a DDSE, with each DDAT being identified by a keyword held in its DKEY attribute. The property definition can be specified by an expression held in the DDPR (Design Data Property) attribute, while a default value for the property (to be used if the expression cannot be evaluated for any reason) can be stored in the DDDF (Design Data Default) attribute.

Unlike a design reference to a catalogue component, which can access only a single catalogue dataset via its DTREF setting, a reference to a design template can access more than one design dataset. A local design dataset is owned directly by the current element, a template design dataset is owned by the first template below the current element, while a current design dataset is at the same level as the current element and has the same owner.

The following diagram illustrates the relative positions of these types of dataset for a simple design hierarchy, namely a Panel Fitting derived by instancing a Design Template which includes a Box primitive:

The full range of pseudo-attributes available for accessing the properties data in the various types of dataset in the Design database are as follows:

You can also derive data values from the parameters of items in the Catalogue database by using the RPRO (Reference Property) pseudo-attribute.