Project files

Keep both project files in version control:

File	Contents
ohi.yaml	Your ontologies, their versions and formats, and project settings.
ohi.lock.json	Download URLs and checksums for those ontologies and their dependencies.

For a walkthrough, see Manage ontology projects.

ohi.yaml

This project uses PROV-O in Turtle format:

format_version: 1
default_format: linkml-yaml
download_dir: .ohi
dependencies:
  - ontology: w3c/prov-o@2013
    format: owl-turtle

Field	Meaning
format_version	Project file version. Must be 1.
default_format	Preferred format for get and add when you omit --format.
download_dir	Subfolder of the project directory where ontologies are downloaded.
dependencies	Ontologies added to the project. Use [] for an empty project.
dependencies[].ontology	Complete namespace/name@version reference.
dependencies[].format	The dependency’s file format.

All fields are required. You can include several versions or formats of an ontology, but each reference and format pair must be unique.

After editing a dependency, run ohi sync to update the lock and downloads. Changing default_format affects future get and add commands, leaving the listed formats unchanged.

Adding a new entry with ohi add removes custom comments and resets formatting.

ohi.lock.json

ohi add updates the lock automatically. ohi sync uses it to restore downloads and updates it when the dependencies in ohi.yaml change.

Field	Meaning
format_version	Lock format. Must be 2.
selections	Release and file URLs for the ontologies you added directly.
files	All files to download, including dependencies.

Each file entry records its release URL (base_url), download URL (url), format and SHA-256 checksum (sha256).

Dependencies use the same format as the ontology you selected. For example, DCAT 3 in Turtle also requires Turtle files for Dublin Core Terms, SKOS and PROV-O.

Use ohi sync after cloning a project or receiving a shared lockfile.

Downloaded files

Downloads are grouped by namespace, ontology and version. For example, DCAT 3 in two formats:

.ohi/w3c/dcat/3/dcat.linkml.yaml
.ohi/w3c/dcat/3/dcat.owl.ttl

The format table lists filename suffixes.

ohi creates a .gitignore inside the download folder to keep downloads out of Git, unless that file already exists. Edit it if you want to commit the downloads too. Keep files you write yourself outside this folder. get --to leaves ignore files unchanged.