Cross Reference Models

Cross referencing models is the mechanism by which you can identify members in different models other than by visual comparison. There are two scenarios: one where an element is created in Model; the other is where it was created in any other system, but is to be imported into Model. The Id field in the SDNF file is not a reliable identifier as it tends to be only a sequential item count produced on the generation of the SDNF file.

Element created in Model

When an element is created in Model it gains a unique internal reference number of the form "=<integer>/<integer>", for example, =13/2305. On export from Model this value, excluding the initial '=' character, is passed through in Packet 10 or 20 in the Mark fields. These are text strings on Records 3 and 3a respectively. Any system importing this file should be able to take this value and store it, or use it to you to identify the Design member in the external steel detailing package.

On Export back to the application, for any member which has this Mark attribute set, the original imported Mark value appears again in the SDNF file. Thus you are able to spot any changes to the model. The AVEVA SDNF Import system, then allows you to modify the existing structure, rather than just replacing it with a copy. In this way, any drawings for example, which may have been produced between Export from and Import back to Model, retain their logical relationships to the steel members.

Element created outside Design

A member created outside Model does not have the Mark field set to be an application internal reference number. The AVEVA SDNF interface would therefore know that it was importing a new element and would create it accordingly, whilst recording the external Mark number as well.

If SDNF detects that there are duplicate external mark numbers as it is preparing to export a model, the internal reference number is used in preference. The SDNF interface then has some chance of identifying the element if it returns from the external package. Refer to Issues Concerning Entity Comparison for further information.