Researching file formats 27: Microstation DGN

This blog post is part of a series on file formats research. See this introduction post for more information.

Update: The official format definition is now online here: MicroStation DGN Family. Comments welcome directly to the Library of Congress.

This format was really a family of formats, and there’s specifically a break between an older version of the format, documented, and a later version of the format, semi-documented. At the time of writing this blog post, I still have some work to do in sorted out all the details and nuances here, when there’s not a ton of information online about this format family.

To continue my frustrations from last week on questionable uses of the term “open” when talking about formats, there’s statements on a legacy website and other places about the format being open, but: “Eligible Bentley subscribers can also request access to Bentley documentation and technical support for the V8 DGN format for internal enterprise systems integration. The contents of the V8 DGN File Format Reference are sufficient to allow a skilled programmer to interpret the data within the Bentley DGN file that Bentley products create and consume.” Then directions to mail or fax the request form. Is that… open??? There was a conversation on a forum about how the format is not very open, if you have to request and get authorized to access it.


The earlier specification was extremely dense and tiring to work my way through, so in a way it was very open and thorough, but I also saw complaints that it wasn’t really that great. For this latter Bentley variant, there’s just a summary of changes or opinions, so overall it may just be a stricter version of what was already established.