Advancing to the Viewpoint.bcf part
In the forum post yesterday, Yorik pointed out that, although part of the specification, the BimSnippet does not have to be treated with high priority. He also referred me to Bernd and Duncan in case of questions arising. As advised, I will consider the BimSnippet in the data model but probably won't implement it right away.
The progress I made today was mostly in understanding the BCF specification in regards to the viewpoint.bcfv file. Multiple viewpoint files can be contained within the folder of one topic. At the beginning of the day I thought that the data model would be finished rather quick but as it turned out the documentation on it is not as concise as one might wish it to be. To be more precise: the whole section about the "Components" element is a bit confusing. It lists multiple "properties", like Selection and Visibility. My intuition says that Selection contains a list of components that are selected, and Visibility specifies whether these components shall be visible or not. But in reality each contains a list of components onto which the values of the attributes of the respective property shall be applied.
This is a bit confusing at first, and still is for me. Because of this ambiguity I decided, for the further data model design, that refer to the related XML schemas rather than the written documentation. For example here you can find the schema for the viewpoint.bcf file.
But since the last time I have worked with XML schemas was in vocational school (I think 2012) I have to refresh my memory on it. For that I will go through the relevant parts of the W3CSchools: XML Schema Tutorial. Tomorrow.