- Author
- Roman Kashitsyn (mmap(blog))
- Published
- 2026-02-28 (a second date, 2026-06-04, is also shown)
- Kind
- Personal blog essay, with examples from several fields
- Original
- mmapped.blog/posts/48-the-third-hard-problem
- Subject
- Software design
What it is
Roman Kashitsyn writes a personal programming blog. The essay adds a third item to the joke list of hard computer science problems. It argues that many design struggles share one cause.
What it says
- Besides naming and cache invalidation, the post names a third hard problem, tree mapping.
- The post says ideas form webs and resist being sorted into hierarchies.
- In file systems, Windows and macOS bundle by application while Linux scatters files by type.
- The post says Alexander's essay argued artificial cities are trees and natural cities are not.
- The post says biological classification by traits is tree mapping, and cladistics is more accurate.
- The post's advice is to be intentional about which links to sacrifice.
What evidence it gives
The essay offers examples and quotations. It cites Christopher Alexander, Steven Pinker, Borges and Bartosz Milewski. It also mentions Bazel as a build tool and Snap as a bundle format. It has no data.
Interests and limits
The essay is argument by example, so the common cause is the author's reading. The examples are illustrations, not a survey. The essay does not test any fix. It says Alexander never gave a blueprint for a natural city.