CQL: Categorical Databases

CQL: Categorical Databases(categoricaldata.net)

39 points by noworriesnate 2 days ago | 11 comments

bob1029 2 hours ago |

> CQL is not a database management system: it neither stores nor updates data.

The same could be said for SQL. How does CQL differ from SQL? If I squint my eyes just a tiny amount, these ideas become really difficult to separate. I was always under the impression that the relational model is based upon many concepts studied in category theory. To my mind, all of the following things are overlapping parts of the exact same monster:

  Set theory
  Category theory
  Graph theory
  Type theory
  Discrete mathematics 
  Relational algebra
  Relational calculus
  Relational modeling
  An actual sql schema

js8 1 hour ago | |

> How does CQL differ from SQL?

SQL is like Java, CQL is like Haskell. SQL has been around and used in production. CQL is a research language, possibly cleaner foundation but YMMV.

The math fields you list are connected, but whether they are the same monster - again it's kinda like claiming all programming languages and implementations are the same (Turing-complete?) monster.

randomNumber7 1 hour ago | | |

SQL is not an imperative programming language.

srean 2 hours ago |

There was a good blog post on how the category theoretic ideas behind this applies to data frames

What Category Theory Teaches Us About DataFrames https://mchav.github.io/what-category-theory-teaches-us-abou...

Discussed on HN at (67 comments)

https://news.ycombinator.com/item?id=47561426

randomNumber7 2 hours ago |

Since Codd's paper showed that the relational model dominates other approaches (for data storage) I would expect a paper that shows categorical database are not affected by this and what benefit they have.

js8 2 hours ago | |

My (amateur) take. CDB model (based on functions) has three advantages over RDB model (based on relations):

1. Easier modelling sum types (inheritance) due to duality.

2. Better handling of null due to labelled null.

3. Better foundation of elementary types (they're just another table ids). (Column stores often do that already, if your question is about storage.)

adrian_b 10 minutes ago | | |

While the relational model is claimed to be based on relations, the vast majority of the "relations" used in practice are functions, not general relations.

A general relation exists only between the columns of a table that are included in a multi-column primary key.

All columns that are not part of the primary key are functions of the primary key.

Most tables used in practice use a single column as the primary key, which is frequently just a number or a UUID. Most databases contain only tables that are functions, without any table that contains general relations.

The most frequently used kinds of joins are just function compositions.

flying_sheep 2 hours ago |

Thanks for the sharing. It looks interesting but I did not dive deep into it. Just wonder how is it different from SQL trigger which can also ensure integrities?

js8 2 hours ago | |

It's not much really, CDBs are based on foreign key relationships as a fundamental building block, rather than on relation.

The difference is more in theory than in practice.

mattsouth 1 hour ago |

Not to be confused with https://cql.hl7.org/ which is the CQL I know of.