I've been looking into this space a bit (after one day realizing that what I'm doing at work is essentially reinventing OLAP abstractions). The way I see it, multidimensional spreadsheeting has evolved into expensive, proprietary ERP and BI software, while the ideas from it end up being repeatedly reinvented in various "excel killer"/"more complicated CRUD" startups without ever reaching their full potential (I'm guessing that would kill the business value). The middle doesn't seem to exist (EDIT or maybe it does?[1]) - I don't know of any actual multidimensional spreadsheet that's accessible to regular people.
There was Egeria[0] featured on HN some years ago, but they've seem to have reverted to a closed beta since then.
The multidimensional spreadsheet is a more complex piece of software than the 2-D, and invites more data that needs to be managed and processed. So it trends to a more database-like system. There might be a niche for small and even-more-complex modeling. It’s hard to open-source something that takes the required investment.
The market kind of died. Lotus Improv had a slick interface but a sucky semantic model. Freebase was for the Mac, good luck with selling business software on the Mac in the 1990’s. Generally, Excel wiped out the Cambrian Explosion of spreadsheet innovation, and the survivors were Excel add-ins with a separate back end (Essbase, TM/1, which are still around). Microsoft never got into it, acquired their way in, and have never shown an aptitude for this area. I think Gresham’s Law pertains to how PivotTables have taken over the MD functionality for Excel
There was Egeria[0] featured on HN some years ago, but they've seem to have reverted to a closed beta since then.
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[0] - https://news.ycombinator.com/item?id=18656746
[1] - https://news.ycombinator.com/item?id=22927875 points out https://www.xcubes.net/, which seems like the "middle" I was looking for.