To use Writing-as-a-user-interface-that-facilitates-thinking effectively, we should be able to find information flexibly in our notes.

We should be able to do searches similar to:

FIND notes that contain "deep learning" or "neural networks"

And queries similar to:

FIND advertizing campaigns that made me buy their product
THAT were clipped from social media

Because I Use-plain-text-files-for-note-taking, the former is easy to do with regex. It’s simple, flexible and incredibly powerful. On the other hand, it is probably equally useful to be able to have semantic search. If I search for “software design”, synonym terms such as “software engineering” are probably also relevant, but this will not pop-up with a pattern-matching search method.

Querying notes using structured information becomes trickier. Notes-can-store-structured-information-in-YAML-header, but Challenges of representing structured information in pure text.