Hode

Last updated April 28, 2022

Authored by:: Brendan Langen

Hode (Higher Order Data Editor) is a Haskell program for reading, writing and searching what might be loosely termed a hypergraph. It’s like a knowledge graph, but more expressive – atoms and relationships can both be members of other relationships, which are labeled and can have any number of members.

Created by Jeffrey Benjamin Brown https://github.com/JeffreyBenjaminBrown

There are three branches to Hode: The RSLT data structure, the Hash language for describing subsets of an RSLT, and the UI, which lets you use the previous two things. A Rslt (Reflexive Set of Labeled Tuples) is a generalization of a knowledge graph. It lets a user easily represent any natural language expression. (A Rslt is isomorphic to what some programmers call a “hypergraph” – but mathematicians claimed that term first, and in math it means something much less expressive.) A Rsltis a collection of expressions, each of which is either a phrase (like “cats”), or a relationship (like “cats have noses”) or a template (like “_ have _”) shared by many relationships. What distinguishes a Rslt from a graph is that relationships can involve any (positive) number of members, and a relationship can itself belong to other relationships. Hash is a language, close to ordinary natural language, for talking about expressions in a Rslt. It offers a concise representation, both for individual Exprs (expressions) in a Rslt, and for queries to retrieve sets of Exprs. The UI displays expressions from your graph using the Hash language.

Examples in action.

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/a (mammals #need calcium) #because (mammals #build bones)

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mammals
	#need _
	7: "mammals #need calcium"

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`/find /eval bob #likes pizza ##with pineapple ###because /it)` -- Returns only the reason, not the full "because" relationship.

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`/find bob #likes /_ /|| bob #dislikes /_` -- Every #likes and every #dislikes statement with bob on the left.