The integration between Tekla Structural Designer and Autodesk Revit software is enabled by the use of GUID (Global Unique IDentifiers) references.

A GUID is a unique number that can be used as an identifier but should not be able to be replicated - with randomly generated GUIDs you should only be duplicating references once every 10-30 trillion GUIDs.

GUID references themselves are a 32 digit hexadecimal reference and are created by a complex algorithm, with the references written as part of a member's properties within the CXL file. We track members based on the GUID reference rather than member size, position, Revit element ID or any other method.

The GUID reference itself is automatically created by Tekla Structural Designer when an object is first inserted into the model. This happens 'behind the scenes' of the program interface and the user is never directly aware of the references.

Please note however, that Revit by default does not use GUID references. Revit instead uses Element ID references, which can be easily duplicated within differing models.

To help avoid any sort of duplication issues, the integration process will assign GUID references to all object instances when models are either imported into Revit or exported from Revit.

Although duplicate GUID references are largely avoided, they can be encountered when using workshared models and attempting to integrate Revit instances which are not owned or are borrowed by another user. See the section below Resolving duplicate GUID references for further information.

Please note that GUID references will be lost on exiting from Revit unless the model is saved first.

It is therefore vital that the Revit model is saved after performing an export to Tekla Structural Designer.

Failure to save will lose the GUID references on exiting the program and remove the ability to communicate any model changes with Tekla Structural Designer.

The integration process will report where duplicate GUID references are detected.

To avoid errors from occurring, the older instance retains its GUID, the newer instance is then assigned a new GUID reference. Both the Revit model and the created .cxl file are then updated accordingly.

The integrator will also help identify the source of duplicates caused by copied instances in Revit.

Important note: Please ensure the Revit model is saved after the export process has been completed.

An API (Application Program Interface) controls the transfer between Tekla Structural Designer and Autodesk Revit. The API is a separate program that sits inside the Tekla Structural Designer Integrator for Autodesk Revit application, and is provided by Autodesk for the Trimble Solutions product development team to use.

The API is the governing factor between the two items of software and controls which object can be passed to and from the software packages. It can also limit what sort of change control can be performed with each category.

• For example, floor category instances can be created or deleted using the API, but they cannot be updated in boundary shape. Therefore, if a floor instance changes boundary shape, the integrator is forced to delete the existing floor instance and create a new instance in its place.

Tekla Structural Designer will transfer the following parameters into Revit:-