Hello,
I am currently working with OpenCities Map 2025 and processing geometry as well as attribute information in FME. The Documentation of the Bentley Map XFM Design (V8) Reader states that XFM data exists and that the newer version uses XAttributes associated with Bentley Select Series 3 and newer design files. It also states that “the DGN V8 Writer currently only writes XFM data in the Select Series 1 form”.
My experience so far is that I can write a DGN file and and OpenCities Map can show without problems the geometry, but the attribute information gets distorted. What I mean by that: in native DGN files the properties display that an element is indeed a native feature, but the in FME created DGN file shows the elements are inferred features containing associated elements. Further in the FME created DGN file it’s possible to create a Map Model but when using the Browse Tool it displays the exception window: Object reference not set to an instance of an object.
This lead to inspecting the Reader-Writer-Workflow. So i started with creating a new feature “Building X0” in a native DGN file (the new feature got displayed as native feature without issues) and then reading it in FME. FME provides the DGNV8XFM-Reader which works fine and displays all necessary information.The Reader followed by an immediate DGNV8-Writer already demonstrates troubling issues: a) the xattributes disappear, b) the igds_xfm_xml attribute (containing relevant information) disappears, c) the clean schema in the Table View (from the Reader) changes to a <no schema> for all elements in the Writer. Opening this newly written file in OpenCities Map expands the issues: d) the “X0” feature now is again an inferred feature according to the properties, e) the other features are now “previous XFM features” (according to the properties as well).
Additional observations have shown that the native DGN-file’s properties contain ‘has feature definition = true’, ‘has properties = true’, ‘xattributes > 0’, while the FME-written DGN-file is defined with ‘has feature definition = true’, ‘has properties = false’, ‘xattributes = 0’.
Based on these observations it appears that the XFM information is not preserved through the DGNV8 writing process, even though the geometry itself is preserved successfully. My question is: Is this the expected behavior due to limitations of the DGNV8 Writer and the newer XAttribute-based XFM model used by OpenCities Map, or is there a supported workflow/workaround that allows creation of DGN files which remain fully functional as Native Features in OpenCities Map?
Kind regards,
Dave