Catalog Operations

In this documentation and examples, the service as described in the previous section on model resource naming is assumed to be https://www.example.com/ermrest.

Service Ad Retrieval

Outside of any catalog context, the service itself offers a brief advertisement of its capability.

The GET method is used to retrieve the service advertisement. This request also serves as a basic health-check of the ERMrest service:

GET /ermrest/ HTTP/1.1
Host: www.example.com

On success, this request yields the service advertisement:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "version": "0.2.0",
  "features": {
    ...
  }
}

Typical error response codes include:

  • 400 Bad Request (on legacy versions lacking this feature)
  • 503 Service Unavailable (if basic service health-check is failing)

The "version" field is the ermrest Python package version as installed. The "features" field is where ERMrest may advertise software features added in subsequent revisions. This allows fine-grained feature detection by clients concerned with exploiting new features, when available, but falling back to simpler access modes if accessing older catalogs.

Known feature flags at time of writing of this document:

  • trs: Service supports the trs(RID) projection functions to retrieve row-level access rights.
  • tcrs: Service supports the tcrs(RID) projection functions to retrieve row-level, per-column access rights.
  • history_control: Service supports tag:isrd.isi.edu:2020,history-capture table annotation to disable history capture.
  • implicit_fkey_index: Service will produce indexes for compound foreign keys to allow index-based joins on these reference patterns.
  • catalog_post_input: The POST /ermrest/catalog method accepts JSON input to customize the catalog ID or initial owner ACL.
  • catalog_alias: The /ermrest/alias resource space and related catalog aliasing features are available.

Generally, absence of a feature flag means the service is running older software which predates the release of the feature. A flag will be present with boolean value true to advertise presence of a feature. Specific flags may be documented with other advertisement values in the future, i.e. to indicate runtime status of a feature which can be disabled selectively by the administrator.

Catalog Creation

The POST method is used to create an empty catalog:

POST /ermrest/catalog HTTP/1.1
Host: www.example.com

This method supports an optional JSON input document:

POST /ermrest/catalog HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "id": desired catalog id,
  "owner": administrative ACL
}

These fields are optional and, if present, override the default behavior obtained in a POST without input:

  • "id": The desired cid to bind (default is a service-generated serial number)
  • "owner": Initial owner-level access control list for the new catalog (default is the requesting client’s identity)

On success, this request yields the new catalog identifier, e.g. 42 in this example:

HTTP/1.1 201 Created
Location: /ermrest/catalog/42
Content-Type: application/json

{
  "id": "42"
}

The configured "owner" will also appear in the "acls" sub-resource of the resulting catalog resource.

Typical error response codes include:

  • 404 Not Found
  • 403 Forbidden
  • 401 Unauthorized

In the rare event that there is a system error during catalog creation, the ERMrest registry of catalogs may retain a record of a claimed catalog identifier without a corresponding catalog database. This record includes the "owner" and only clients authorized by that access control list may retry catalog creation with the same desired catalog id.

Catalog Retrieval

The GET method is used to get a short description of a catalog by its canonical identifier or an alias:

GET /ermrest/catalog/42 HTTP/1.1
Host: www.example.com

On success, this request yields a catalog description:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "id": "42",
  "alias_target": target catalog identifier,
  "rights": {
    "owner": boolean,
    "create": boolean
  },
  "acls": {
    "owner": access control list,
    ...
  },
  "annotations": {
    "tag:isrd.isi.edu,2018:example": {"value": "my example annotation"}
  },
  "snaptime": "2PX-WS30-E58W",
  "features": {
    ...
  }
}

The fields of this representation are:

  • "id": The identifier for the catalog being addressed (may be an alias or storage catalog identifier).
  • "alias_target": The canonical identifier for the storage catalog (only present when "id" is showing an alias instead).
  • "snaptime": The identifier for the snapshot being addressed.
  • "rights": A summary of rights for the requesting client.
  • "acls": Configured access control lists for this catalog.
  • "annotations": Configured annotations for this catalog.
  • "features": The service features advertisement as described in the Service Ad Retrieval request.

This representation summarizes the catalog which is affectively addressed by the catalog URL. Other catalog sub-resources described in this API documentation are likewise available relative to this catalog URL prefix. Access to sub-resources for catalog, schema, and content management and access are consistent whether the catalog URL prefix is using a canonical storage catalog cid or a catalog alias.

Typical error response codes include:

  • 404 Not Found
  • 403 Forbidden
  • 401 Unauthorized

Catalog Deletion

The DELETE method is used to delete a catalog:

DELETE /ermrest/catalog/42 HTTP/1.1
Host: www.example.com

There are two cases for catalog deletion via this API:

  1. When DELETE /ermrest/catalog/ alias names a catalog by alias: equivalent to DELETE /ermrest/alias/ alias while the underlying storage catalog is unaffected.
  2. When DELETE /ermrest/catalog/ cid names a storage catalog identifier, the catalog and its content are destroyed, unbinding (but not destroying) any existing aliases which have cid as their "alias_target".

On success, this request yields a description:

HTTP/1.1 204 No Content

Typical error response codes include:

  • 404 Not Found
  • 403 Forbidden
  • 401 Unauthorized

Catalog Alias Creation

The POST method is used to create an alias resource:

POST /ermrest/alias HTTP/1.1
Host: www.example.com

This method supports an optional JSON input document:

POST /ermrest/alias HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "id": desired alias id,
  "owner": administrative access control list,
  "alias_target": existing storage catalog id
}

These fields are optional and, if present, override the default behavior obtained in a POST without input:

  • "id": The desired alias to bind (default is a service-generated serial number)
  • "owner": Initial access control list for the alias (default is the requesting client’s identity)
  • "alias_target": Storage catalog to bind with the new alias (default unbound)

An unbound alias can reserve the alias for future use by clients permitted by the adminstrative access control list.

On success, this request yields the new catalog alias, e.g. my_alias in this example:

HTTP/1.1 201 Created
Location: /ermrest/catalog/42
Content-Type: application/json

{
  "id": "my_alias"
}

The configured "owner" and "alias_target" will also appear in the resulting alias resource.

Typical error response codes include:

  • 404 Not Found
  • 403 Forbidden
  • 401 Unauthorized

Catalog Alias Retrieval

The GET method is used to get a short description of an alias:

GET /ermrest/alias/my_alias HTTP/1.1
Host: www.example.com

On success, this request yields a description:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "id": "my_alias",
  "owner": administrative access control list,
  "alias_target": "42"
}

The fields of this representation are:

  • "id": The alias identifier.
  • "owner": The access control list granting permission to manage this alias.
  • "alias_target": The canonical identifier for the storage catalog (may be null for unbound aliases.

Typical error response codes include:

  • 404 Not Found
  • 403 Forbidden
  • 401 Unauthorized

Catalog Alias Update

The PUT method is used to modify the configuration of an alias:

PUT /ermrest/alias/my_alias HTTP/1.1
Host: www.example.com
Content-Type: application/json

{
  "id": "my_alias",
  "owner": new administrative access control list,
  "alias_target": new target catalog identifier
}

Either field is optional and defaults to leaving the respective configuration unchanged:

  • "owner": Set a new administrative access control list for the alias.
  • "alias_target": Bind or re-bind the alias to the specified storage catalog.

For ease of use, the "id" field is also accepted as input, so that an existing alias representation could be edited and resubmitted. However, the included "id" field MUST match the alias identifier in the URL.

On success, this request yields a description of the updated alias:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "id": "my_alias",
  "owner": administrative access control list,
  "alias_target": "42"
}

Typical error response codes include:

  • 404 Not Found
  • 403 Forbidden
  • 401 Unauthorized

Catalog Alias Deletion

The DELETE method is used to delete a catalog alias:

DELETE /ermrest/alias/my_alias HTTP/1.1
Host: www.example.com

On success, this request yields a description:

HTTP/1.1 204 No Content

Typical error response codes include:

  • 404 Not Found
  • 403 Forbidden
  • 401 Unauthorized