Lab 01 — Extend the Domain Model

Goal

Add a new entity Location to the domain model, link it to existing entities, and verify your changes compile and test cleanly.

Background

This lab teaches you how CAP's domain model (db/schema.cds) is structured and how new entities relate to the rest of the schema. You'll learn:

• How to declare a CDS entity with typed elements
• How cuid and managed mixins add standard fields automatically
• How Association links two entities

Steps

Step 1 — Add the Location entity

Open db/schema.cds and add the following entity at the end of the star.wars namespace block (after the last entity or view):

/**
 * A named location in the Star Wars universe (not a full Planet, just a place).
 */
entity Location : cuid, managed {
    name        : String @mandatory;
    description : String(500);
    planet      : Association to Planet;
}

Step 2 — Verify the model compiles

From cap/:

cds compile db --to json > /dev/null && echo "Model OK"

You should see Model OK. If you get an error, check your syntax carefully.

Step 3 — Add a basic test

Open test/model.test.js and add a test inside the describe('Star Wars CDS Model Tests', ...) block:

describe('Location entity', () => {
    let db
    before(async () => { db = await cds.connect.to('db') })
    after(async () => {
        await db.run(DELETE.from('star.wars.Location').where({ name: { like: '%-lab01' } }))
    })

    it('inserts a Location with an auto-generated ID', async () => {
        await db.run(INSERT.into('star.wars.Location').entries({
            name: 'Mos Eisley-lab01',
            description: 'A wretched hive of scum and villainy',
        }))
        const [loc] = await db.run(
            SELECT.from('star.wars.Location').where({ name: 'Mos Eisley-lab01' })
        )
        assert.ok(loc?.ID, 'Location.ID should be auto-generated')
        assert.equal(loc.name, 'Mos Eisley-lab01')
    })
})

Step 4 — Run the tests

npm run test

All existing tests should still pass, and your new test should pass too.

Expected Outcome

• cds compile db completes without errors
• npm run test shows the new Location test passing
• The entity has a UUID primary key, createdAt, createdBy, modifiedAt, modifiedBy (from cuid + managed)

Hints

• The star.wars namespace applies to everything in schema.cds because of the namespace star.wars; declaration at the top.
• cuid is from @sap/cds/common — it adds key ID : UUID.
• managed is from @sap/cds/common — it adds the four audit fields.
• You don't need to reference cap/db/sqlite/index.cds — it automatically includes schema.cds.

Stretch Exercise

Add a Composition of many Film2Locations so Films can reference Locations (like filming sites in the lore). Follow the pattern of Film2People in schema.cds.