Ask HN: Designs in which information stored in the system outlives it?

I am currently researching &#x2F; designing a kind of annotation system for digital materials (PDFs, EPUBs, scanned books) meant primarily for experts to create annotations over the source material of their domain. The system will allow quick navigation, linking, referencing, creating hierarchies of tags, scripting and heavy domain-specific customization.<p>Think professor of literature annotating thousands of pages of Dumas over the span of months for easier lookup later &#x2F; notes &#x2F; categorization &#x2F; research, creating a graph of knowledge you can interact with in the process, where facts are referencing the source material or building on other facts.<p>This system might be used for a while by few people and after few months &#x2F; 5 years &#x2F; a decade it might be retired.<p>What general advice do you have to make sure that when it happens, someone (people who found the files on the internet, students, archivists, former users) can recover the data without much burden?