Datomic Knowledgebase - Recent questions tagged datamodel

How do you add relationship properties, e.g. the time a person met another person?

Mon, 07 Nov 2022 08:35:28 +0000

I have some experience with Neo4j / cypher. In cypher relationships are first-class citizens, so they can have properties, which I really like.

How do I do something similar with datalog? Do I have to have a "mapping entity" in between two entities that have a relationship?

How do you visualize your schema ?

Fri, 08 Jul 2022 15:58:59 +0000

Hi I made a quick search in this channel to find tools for visualizing Datomic schema. The most promising tool I found was Hodur Datomic Schema. This is nice because you can create entity types and connect them through attributes. I would like to share with you an example I made. Here is a simple Datomic Schema in Hodur Descriptive Domain Modeling Engine EDN format and here is my clojure gist to run and output the result. There is a better Hodur schema visualization using GoJS library but I have not figured out yet how to make the http web server to work with the Hodur visualizer clojurescript it seems users have issues with it.

OK that said, I am aware that in Clojure you are trying to break away from entity types, object types in general and work with attribute oriented modeling. But the way you are modeling schema you cannot escape from namespace prefixes and these imply entity types. In any case it is standard practice in any significant large IT project that users want to see and work easily on a white-board with some kind of graph data model that represents an abstract data model. That was the scope of Hodur I guess. In the RDBMs world and more recently in Graph DBMS there are great tools to visualize both the schema and data. So how do you visualize the data modeling process and it's evolution in large projects using Datomic ?

I had a quick look at schema-cartographer.

It creates schema-cartographer dependent edn files when you download schema transactions and schema files from their Web APP UI (see schema.edn) and (schema-txs.edn)
You have to work everything on the UI. But I think you cannot download and run this independently on your premises.
There is this Create a schema file for an existing annotated ON PREM database from a REPL but again you have to load the resulting output file in the UI that resides at https://schema-cartographer.com
It is not flexible enough and it will result in poor visualization when you have a big schema and/or you want to view part of the schema
The schema-cartographer UI says GoJS 2.0 evaluation (c) 1998-2019 Northwoods Software Not for distribution or production use gojs.net

So what tool Cognitect people use to visualize Datomic schema. Is that the tool ?

What indexes does Datomic use?

Mon, 19 Oct 2020 18:01:45 +0000

What indexes does Datomic use?

Does Datomic have tables?

Mon, 19 Oct 2020 17:22:20 +0000

Does Datomic have tables?

Don’t all those indexes take up a lot of storage space?

Mon, 19 Oct 2020 17:16:14 +0000

Don’t all those indexes take up a lot of storage space?

How is Datomic different from a traditional RDBMS? A NoSQL database?

Mon, 19 Oct 2020 17:01:16 +0000

How is Datomic different from a traditional RDBMS? A NoSQL database?

What data types are supported by Datomic?

Mon, 19 Oct 2020 17:01:01 +0000

What data types are supported by Datomic?

Can I remove an index?

Mon, 19 Oct 2020 16:59:30 +0000

Can I remove an index?

Does Datomic use sharding?

Mon, 19 Oct 2020 16:43:33 +0000

Does Datomic use sharding?

Against which index should I target my query?

Mon, 19 Oct 2020 16:03:52 +0000

Against which index should I target my query?

How should I model my data in Datomic?

Mon, 19 Oct 2020 15:40:32 +0000

How should I model my data in Datomic?

How do I prevent users from adding invalid data?

Mon, 19 Oct 2020 15:39:37 +0000

How do I prevent users from adding invalid data?

What is a datom?

Mon, 19 Oct 2020 15:20:32 +0000

What is a datom?

What is Datomic’s data model?

Mon, 19 Oct 2020 15:18:56 +0000

What is Datomic’s data model?

How do I create my schema?

Mon, 19 Oct 2020 15:13:34 +0000

How do I create my schema?

Does Datomic support conditional operations?

Mon, 19 Oct 2020 14:43:46 +0000

Does Datomic support conditional operations?

Does Datomic support schema-less data?

Mon, 19 Oct 2020 14:31:20 +0000

Does Datomic support schema-less data?