Building with DHL

DHL is the language Mandala uses to write down how a business works: what a record is, who may change it, how, and when it must refuse. A contract in DHL is short, readable Markdown, and the engine enforces it on every change, whoever asks: you, a colleague, an API client or your accomplice.

From one contract Mandala derives:

• the records and their history, each change signed by who made it;
• the back office in Data, with forms, previews and refusals in words;
• your accomplice's tools, one per action and query;
• a generated HTTP, GraphQL and gRPC API;
• how changes merge when several devices work offline.

 contract (.dhl)  ──compile──►  artifact (schema + Wasm, identified by its hash)
       │                              │
       │  optional UI file (.ui.md)   ├──► Data page: tables, forms, refusals in words
       └──────────────────────────────┼──► accomplice tools
                                      └──► /v1 API (REST, GraphQL, gRPC)

Learn

1. DHL concepts — contracts, records, actions, queries, signers.
2. Tutorial: your first contract — write, try and install your first contract in 20 minutes.

Reference

• DHL language reference — the file format and every block.
• DHL types — the value types.
• DHLQ query reference — the query language.
• UI files — labels, formats, forms and refusals in words.
• Durability classes — how soon a write is on disk.
• Merge rules for sync — how concurrent changes merge.
• Upgrading a contract — changing a contract that already has records.
• The generated API — the HTTP API every contract gets.

Practice

• The Workbench — write, try and install from the app.
• Testing contracts — check that the rules accept and refuse what they should.
• DHL best practices — patterns that age well.
• Example contracts — real contracts to read and copy.