---
layout: default
navsection: api
title: "Metadata properties"
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{% comment %}
Copyright (C) The Arvados Authors. All rights reserved.

SPDX-License-Identifier: CC-BY-SA-3.0
{% endcomment %}

Arvados allows you to attach arbitrary properties to "collection":methods/collections.html, "container_request":methods/container_requests.html, "link":methods/links.html and "group":methods/groups.html records that have a @properties@ field.  These are key-value pairs, where the value is a valid JSON type (string, number, null, boolean, array, object).

Searching for records using properties is described in "Filtering on subproperties":methods.html#subpropertyfilters .

h2. Reserved properties

Components that ship with Arvados may automatically set properties on objects. These usually help track provenance or provide additional link metadata. These properties usually have a key that starts with @arv:@, and can always be set even when the system is configured with a strict vocabulary.

table(table table-bordered table-condensed).
|_. Property name|_. Appears on|_. Value type|_.Description|
{% comment %}
The arv:git* container properties, and the associated Git commands, primarily come from arvados_cwl.executor.ArvCwlExecutor.get_git_info.
{% endcomment -%}
|arv:gitBranch|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with the name of the branch checked out (the output of @git rev-parse --abbrev-ref HEAD@)|
|arv:gitCommitter|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with the name and email address of the committer of the most recent commit (the output of @git log --format='%cn <%ce>' -n1 HEAD@)|
|arv:gitCommit|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with the full checksum of the most recent commit (the output of @git log --format='%H' -n1 HEAD@)|
|arv:gitDate|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with the commit date of the most recent commit in RFC 2822 format (the output of @git log --format='%cD' -n1 HEAD@)|
|arv:gitDescribe|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with the name of the most recent tag that is reachable from the most recent commit (the output of @git describe --always --tags@)|
|arv:gitOrigin|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with the URL of the remote named @origin@, if set (the output of @git remote get-url origin@)|
|arv:gitPath|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with the absolute path of the checkout on the filesystem|
|arv:gitStatus|container request, collection of type=workflow|string|When @arvados-cwl-runner@ is run from a Git checkout, this property is set with a machine-readable summary of files modified in the checkout since the most recent commit (the output of @git status --untracked-files=no --porcelain@)|
|arv:workflowMain|collection of type=workflow|string|Set on a collection containing a workflow created by @arvados-cwl-runner --create-workflow@, this is a relative reference inside the collection to the entry point of the workflow.|

The following system properties predate the @arv:@ key prefix, but are still reserved and can always be set.

table(table table-bordered table-condensed).
|_. Property name|_. Appears on|_. Value type|_.Description|
|type|collection|string|Appears on collections to indicates the contents or usage. See "Collection type values":#collectiontype below for details.|
|container_request|collection|string|The UUID of the container request that produced an output or log collection.|
|docker-image-repo-tag|collection|string|For collections containing a Docker image, the repo/name:tag identifier|
|container_uuid|collection|string|The UUID of the container that produced a collection (set on collections with type=log)|
|cwl_input|container_request|object|On an intermediate container request, the CWL workflow-level input parameters used to generate the container request|
|cwl_output|container_request|object|On an intermediate container request, the CWL workflow-level output parameters collected from the container request|
|template_uuid|container_request|string|For a workflow runner container request, the workflow record that was used to launch it.|
|username|link|string|For a "can_login":permission-model.html#links permission link, the unix username on the VM that the user will have.|
|groups|link|array of string|For a "can_login":permission-model.html#links permission link, the unix groups on the VM that the user will be added to.|
|image_timestamp|link|string|When resolving a Docker image name and multiple links are found with @link_class=docker_image_repo+tag@ and same @link_name@, the @image_timestamp@ is used to determine precedence (most recent wins).|
|filters|group|array of array of string|Used to define "filter groups":projects.html#filtergroup|

h3(#collectiontype). Collection "type" values

Meaningful values of the @type@ property.  These are recognized by Workbench when filtering on types of collections from the project content listing.

table(table table-bordered table-condensed).
|_. Type|_.Description|
|log|The collection contains log files from a container run.|
|output|The collection contains the output of a top-level container run (this is a container request where @requesting_container_uuid@  is null).|
|intermediate|The collection contains the output of a child container run (this is a container request where @requesting_container_uuid@ is non-empty).|
|workflow|A collection created by @arvados-cwl-runner --create-workflow@ containing a workflow definition.|

h2. Controlling user-supplied properties

Arvados can be configured with a vocabulary file that lists valid properties and the range of valid values for those properties.  This is described in "Metadata vocabulary":{{site.baseurl}}/admin/metadata-vocabulary.html .

Arvados offers options to set properties automatically and/or prevent certain properties, once set, from being changed by non-admin users.  This is described in "Configuring collection's managed properties":{{site.baseurl}}/admin/collection-managed-properties.html .

The admin can require that certain properties must be non-empty before "freezing a project":methods/groups.html#frozen .