About

Schema is an open-source component of Memri. It functions as the single source of truth of the data model of your personal data. The latest stable version can be explored at schema.memri.io.

This repository contains code to export schema definitions for both the Pod and the iOS app. This is only necessary if you [change the schema](#Changing the schema), as they both repositories already include a generated schema.

Local build/install

To run the code, make sure you have Node.js and npm installed and run:

cd tools/
npm install

To run the explorer (web app): node explorer.js
To test whether the schema contains inconsistencies: node test.js
To export the schema for the Pod: node export_schema_pod.js
To export the schema for the iOS application: node export_schema_ios_application.js
To export the schema for the Web application: node export_schema_web_application.js
To export the schema for the Indexers: node export_schema_indexers.js

The schema

The schema consists of 2 parts:

• Type Hierarchy
• Edge & Property Hierarchy

Item Hierarchy

All the data points in Memri are called items, e.g. a Person, a Location or a Video. The top level item is called Item, and all other items inherit all the properties and edges of Item.

The Item hierarchy defines:

• What types of Items exist
• What properties and edges an Item can have
• How Items are positioned in the hierarchy

Edge & Property Hierarchy

Items can have Edges and Properties, which are in the same hierarchy.

The Edge & Property hierarchy defines:

• What types of Edges and Properties exist
• What types Edges and Properties expect
• How Edges and Properties are positioned in the hierarchy

Edges

Edges are connections to other items, for instance, there might be an 'attends' edge from a Person to an Event. By default, edges are one-to-many relations: An item can have any number of edges of an allowed edge type.

Properties

Where edges connect to other items, properties connect directly to a value of a primitive type, for instance, an item could have a 'name' property of type 'String'. Properties are always one-to-one relations: An item can only have single value for a property.

Primitive types

The primitive types that are supported by the data model are defined in TypeHierarchy/primitive. All properties must expect one of these types.

Changing the schema

The schema is stored as two directory trees for the two hierarchies, with a set of files to define their characteristics.

The information of an Item is stored as follows:

• The directory location defines its position in the hierarchy
• The directory name, and the name of the json file it contains, is the name of the item
• The json file specifies the actual item:

{
  "description": "A short description of the item.",
  "properties": [
    "someProperty"
  ],
  "relations": {
    "someEdge": {
      "sequenced": false,
      "singular": false
    }
  },
  "foregroundColor": "#ffffff",
  "backgroundColor": "#3a5eb2"
}

The information of an edge or property is stored as follows:

• The directory location defines its position in the hierarchy
• The directory name, and the name of the json file it contains, is the name of the edge or property
• The json file specifies the actual edge or property:

{
  "description": "A short description of the edge or property.",
  "type": "ExpectedItemTypeOrPrimitive"
}

If you added an Item, Edge or Property, make sure to run node test.js to see whether there are inconsistencies.

If there aren't, use the node export_schema_X.js scripts to create the schemas for the projects you are working on, and overwrite them in the corresponding projects and rebuild those. We plan to automate this process further in the near future to improve the developer experience.