Dolfin Language Support

Rich language support for Dolfin, a strongly-typed ontology language for building knowledge graphs.

The language server runs entirely inside the extension via WebAssembly, no separate binary to install, no Rust toolchain required.

Features

Diagnostics

Parse errors and semantic issues are reported inline as you type.

Hover

Hover over any concept, property, or prefix to see its type, documentation, and declaration location.

Completions

Context-aware completions for keywords, declared concepts, properties, and prefix aliases, including cross-file symbols from your full package.

Go to Definition

Jump to the declaration of any concept, property, or prefix, even across files in the same package.

Find All References

Find every use of a concept or property across all .dlf files in the workspace.

Rename Symbol

Rename any concept, property, or prefix; all references in the package are updated atomically.

Document Symbols

The Outline view and breadcrumbs show all declarations in the current file, letting you navigate large ontologies quickly.

Code Lens

Inline reference counts appear above every concept, property, and rule. Click to jump straight to Find All References.

Semantic Highlighting

Concepts, properties, prefixes, keywords, and literals are coloured by semantic role, not just syntactically.

Quick Fix (Code Actions)

One-click fixes for common issues such as undefined prefixes.

Getting Started

1. Install the extension from the VS Code Marketplace.
2. Open a folder containing .dlf files.
3. The language server activates automatically when you open a .dlf file.

No configuration is required. The extension indexes all .dlf files in the workspace on startup so cross-file features work immediately.

Dolfin Syntax at a Glance

prefix <https://example.org/hr/> as hr

concept Person:
  has name : one string
  has age  : optional int

concept Employee:
  sub Person
  has employeeId : one string
  has department : one Department

concept SeniorEmployee:
  sub Employee

concept Department:
  has title : one string

rule senior_employee:
  match 
    ?e a Employee
      age [ >= 40 ]
  then
    ?e a SeniorEmployee

Requirements

• VS Code 1.82 or later
• A workspace folder containing .dlf source files

no additional dependencies.

Extension Settings

This extension contributes no settings. Everything works out of the box.

License

MIT © 2026 Dolfin Team