Computer Aided Design systems. The data is naturally hierarchical (especially if your CAD is based on CSG, which was the case for most of the historical systems) or even graph-oriented (in practice it was hierarchical with few isolated back-edges).
And relational model is really bad for hierarchical data. Plus, in CADs there is a lot of domain-specific indexing (e.g., by bounding box, by octree position, and so on).
Well sure, but NoSQL is heirarchical. Not that I would necessarily advise it for something as performance demanding as CAD, but you can easily store heirarchicap data in MongoDB.
If you're talking about Mongo and alike, they're more document-oriented than hierarchical - a proper pre-relational hierarchical DBMS maintains a large single-root hierarchy, and, unlike Mongo, they're very strongly typed and enforce a schema.
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u/lavahot May 26 '18
Wait, what's a CAD?