Simple access to data in Solid pods through LDflex expressions

This library brings the LDflex language to Solid by:

1. providing a JSON-LD context for Solid
2. binding a query engine (Comunica)
3. exposing useful data paths

LDflex expressions occur for example on Solid React components, where they make it easy for developers to specify what data they want to show. They can also be used as an expression language in any other Solid project or framework.

Once you obtain the solid.data object, start writing data paths from the following entry points.

The solid.data.user path can query data about the currently logged in user, such as:

• solid.data.user.firstName yields the user's first name(s)
• solid.data.user.email yields the user's email address(es)
• solid.data.user.friends yields the user's friend(s)
• solid.data.user.friends.firstName yields the user's friends' first name(s)

The solid.data[url] path can query data about any subject by URL, such as:

• solid.data['https://ruben.verborgh.org/profile/#me'].firstName
• solid.data['https://ruben.verborgh.org/profile/#me'].email
• solid.data['https://ruben.verborgh.org/profile/#me'].friends
• solid.data['https://ruben.verborgh.org/profile/#me'].friends.firstName

As you can see in the above examples, an LDflex path starts with an entry point and is followed by property names, which can be:

• abbreviations such as firstName (which expands to http://xmlns.com/foaf/0.1/givenName)
• prefixed names such as foaf:givenName (which expands to http://xmlns.com/foaf/0.1/givenName)
• full URLs such as http://xmlns.com/foaf/0.1/givenName

The abbreviations and prefixed names are expanded using the JSON-LD context. You can find some inspiration about what to ask for in this context.

You can access data using any vocabulary you want and, when included in the JSON-LD context, in multiple ways. For example:

• FOAF:
  • solid.data.user.name
  • solid.data.user.foaf_name
  • solid.data.user['foaf:name']
  • solid.data.user['http://xmlns.com/foaf/0.1/name']
• vCard:
  • solid.data.user.vcard_fn
  • solid.data.user['vcard:fn']
  • solid.data.user['http://www.w3.org/2006/vcard/ns#fn']
• Schema.org:
  • solid.data.user.schema_name
  • solid.data.user['schema:name']
  • solid.data.user['http://www.schema.org/name']
• Custom:
  • solid.data.user['http://example.org/my-ontology/name']

npm install @solid/query-ldflex

const { default: data } = require('@solid/query-ldflex');

const ruben = data['https://ruben.verborgh.org/profile/#me'];
showProfile(ruben);

async function showProfile(person) {
  const label = await person.label;
  console.log(`\nNAME: ${label}`);

  console.log('\nTYPES');
  for await (const type of person.type)
    console.log(`  - ${type}`);

  console.log('\nFRIENDS');
  for await (const name of person.friends.firstName)
    console.log(`  - ${name} is a friend`);
}

<script src="solid-auth-client.bundle.js"></script>
<script src="solid-query-ldflex.bundle.js"></script>

document.addEventListener('DOMContentLoaded', async () => {
  const user = solid.data.user;
  alert(`Welcome, ${await user.firstName}!`);
});

LDflex expressions are actual JavaScript—not strings. There are times when strings are more useful though, such as when building declarative components that take LDflex expressions.

The solid.data object exports a resolve interface that transforms a string expression into an actual LDflex path. This string is appended to solid.data to obtain the resulting path. For example:

• solid.data.resolve('.user.firstName') becomes the path solid.data.user.firstName
• solid.data.resolve('["https://example.org/"].label') becomes the path solid.data["https://example.org/"].label

For convenience, the starting dot and quotes inside of braces can be omitted. The following strings will all resolve:

• '.user.firstName'
• 'user.firstName'
• '["https://example.org/"].label'
• '[https://example.org/].label'

©2018–present Ruben Verborgh, MIT License.