Your first Rell app on Chromia

Start here to build Chromia applications with Rell, the language used to write Chromia decentralized applications (dapps). Over the course you build BookView, a small book review app, and along the way you learn to model data, write queries, and sign transactions.

What is Chromia?

Chromia is a relational blockchain: it combines a relational database with blockchain capabilities. Because of this, building a dapp on Chromia feels familiar whether your background is enterprise software, game development, or smaller projects.

Chromia also has its own language, Rell, built for both blockchain and database work. Rell is statically typed and more expressive, improves database security, and its data definitions can be up to 7x more compact than SQL.

For more on Chromia and how it is built, read the Chromia overview.

About the dapp

You build a book review app. Users can add books, write reviews, and give ratings. You also learn several ways to narrow down and filter reviews by specific criteria.

What will I learn?

When you finish, you will be able to:

• Define entities and the relationships between them.
• Fetch data with queries and apply filters to the results.
• Apply basic validation to protect your app.
• Sign and commit transactions with cryptographic signatures.

The result is a working dapp, running on Rell and the Chromia blockchain, where users add books, write reviews, and fetch reviews using their own filters.

Related materials

The course builds on the following documentation, which explains the concepts and approaches it uses:

Repository link

You can find the full source code for this course in the book review course repository.