Background
In his article “Complex Information Processing”, Nelson expands upon Bush’s idea of the “memex” to explain the necessary developments for creating a file structure that would allow for the storage of personal files and act “as an adjunct for creativity”. I was glad to read this article shortly after having read Bush’s famous piece (“As We May Think”), because it seemed that in the twenty years between the articles were published, a great deal of technical knowledge had been gained. Nelson, however, expressed some regret that his vision for a computer-based file structure that could be used on a personal—rather than strictly professional—level had not yet come to fruition. He attributed the lack of productivity to high cost, little sense of need, and uncertainty about system design.
Nelson did not dwell on the first two arguments, but rather focused almost exclusively on the third. He proposed that a computer with the capabilities he desired required three parts:
- information structure (zippered lists)
- file structure (Evolutionary List File, ELF)
- file language (Personalized Retrieval, Indexing, and Documentation Evolutionary System, PRIDE)
Nelson explained that this kind of system would have features “specifically adapted to useful change”:
- it would be able “to sustain changes in the bulk and block arrangements of its contents”
- it would permit dynamic outlining–the process by which the change in one text sequence guides an automatic change in the next sequence
- it would allow multiple drafts to remain on file for comparison for an indefinite time period
- it would be simple to use
These features make the system evolutionary.
Evolutionary List File (ELF)
In order to ensure the simplicity of the evolutionary system, the file structure of ELF consists of zippered lists (which allow for the linkage of two or more related lists). ELF consists of:
- entries—discrete data ranging from text to symbols; can be created at any time
- lists—an ordered set of entries; can be combined, rearranged, or divided
- links—a connector in one entry that links it to another entry; any number of links can be created
Its basic structure is rendered here: Complex Information Technology Picture
Nelson proposes that this structure is so evolutionary because of its “psychological virtue”—its simplicity, its ability to “be easily taught to people who do not understand computers”.
Speaking as someone with little technical experience, I think that’s a goal extremely relevant to computer users of Nelson’s time and our time alike.