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

SPDX-License-Identifier: CC-BY-SA-3.0
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Arvados allows you to attach arbitrary properties to @collection@, @container_request@, @link@ and @group@ 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

The following properties are set by Arvados components.

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 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_inputs|object|container_request|On an intermediate container request, the CWL workflow-level input parameters used to generate the container request|
|cwl_outputs|object|container_request|On an intermediate container request, the CWL workflow-level output parameters collected from the container request|
|template_uuid|string|container_request|For a workflow runner container request, the workflow record that was used to launch it.|
|username|string|link|For a "can_login":permission-model.html#links permission link, the unix username on the VM that the user will have.|
|groups|array of string|link|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|string|link|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|array of array of string|group|Used to define "filter groups":projects.html#filtergroup|

h3. Collection "type" values

Meaningful values of the @type@ property.

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).|

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 .