Design Datasets

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 (and subsequently referenced) by a keyword or property name by a keyword held in its DKEY attribute.

The property definition can be specified by an expression held in the Design Data Property (DDPR) attribute, while a default value or expression for the property (which is used if the DDPR expression cannot be evaluated for any reason) can be stored in the Design Data Default (DDDF) attribute.

Unlike a design reference to a Catalog component, which can access only a single Catalog 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, and

• 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 hierarchy:

The pseudo‑attributes available for accessing the properties data in the various types of dataset are as follows:

Note:
The dataset attributes PRLS, PROP and PRDE are also used to refer to Catalog dataset properties. To query any of these attributes, a search for a Catalog dataset will be made first; if this fails, a search for a design template dataset will be made.

Most commonly, a design attribute value will be defined in terms of a design property by using the Current Design Dataset Property (CDPR) attribute. The CDPR can also be used to define a property in one dataset in terms of a property in another dataset. When a CDPR is used in a rule for a component whose owner can own datasets, the current datasets will be those at the same level as the component: otherwise, the current datasets will be those under the first dataset-owning element above the component. When a CDPR is used in a property expression within a dataset, it refers to a property in the current dataset for the item at which CDPR is evaluated.

When used in a querying command or in an expression (for example, when defining a parameterization rule), the attributes for a specific property are identified by the DKEY for that property. For example:

Note:
Usually default values are assigned to properties, which are then used to evaluate expressions during the creation of a design template. Which allows the user to see the template geometry in a graphical view, at a practical scale, as defined. Thus a default value for LENG in the last example would allow a sensible XLEN dimension to be evaluated from the rule for display purposes. When instanced in a design, the value of the LENG property would be derived from, say, a design parameter and the rule would be re‑executed to give the correct XLEN.