Spatial Views (preview)#

Warning

This feature is in preview and therefore is not feature complete or may have some bugs.

As of Arches version 6.1.0, it is possible to create spatial views of resource instance data that can be consumed by any client that supports PostGIS spatial views.

Currently the preview only allows the spatial views to be created in Django admin by managing the Spatial Views entities.

The spatial views are only able to represent the data in a flattened state, meaning that the data in nested cards are flattened into a single comma separated attribute value, with the card sort order honoured. Therefore, it is important to consider how to attribute the views being created.

Spatial Views Model Schema#

The Spatial View model schema is defined as follows:

Spatialviewid

Unique identifier for the spatial view.

Schema

The database schema that the spatial view belongs to. public is used by default but if another is used then it must have already been created in the database.

Slug

This is will be joined with the Schema to form the name of the spatial view. This value must follow slug format of only lower-case letters, numbers, and hyphens. It cannot start with a number.

Description

The text that is added as a comment on the spatial view in the database , which can be accessed as metadata for consuming clients where supported. pg_featureserv for example will present this as the layer description.

Geometrynodeid

The UUID of the geojson-feature-collection node that underpins the geometry of the spatial view.

Ismixedgeometrytype

Boolean value that indicates whether the geometry of the spatial view is a mix of different geometry types. This is ideal where the spatial view will be used by a vector tile service.

Default value is false.

Attributenodes

A JSON object that contains a list of attribute object defining the UUIDs of the nodes that comprise the attributes of the spatial view and a text description of that attribute for metadata.

Note

The name of the attributes are automatically generated from the node name using Postgresql a compliant format.

[
    {
        "nodeid": "77e8f28d-efdc-11eb-afe4-a87eeabdefba",
        "description": "construction_phase_type"
    }, {
        "nodeid": "676d47ff-9c1c-11ea-b07f-f875a44e0e11",
        "description": "asset_name"
    }, {
        "nodeid": "325a2f33-efe4-11eb-b0bb-a87eeabdefba",
        "description": "primary_reference_number"
    }, {
        "nodeid": "ba345577-b554-11ea-a9ee-f875a44e0e11",
        "description": "description"
    }, {
        "nodeid": "b2133e72-efdc-11eb-a68d-a87eeabdefba",
        "description": "use_phase_period"
    }, {
        "nodeid": "b2133e6b-efdc-11eb-aa04-a87eeabdefba",
        "description": "functional_type"
    }, {
        "nodeid": "77e8f29d-efdc-11eb-b890-a87eeabdefba",
        "description": "cultural_period"
    }
]

nodeid: The UUID of the node that needs adding. This must be in the same model and the Geometrynodeid.
description: The text description of the attribute, which will be added as metadata.

Isactive

Boolean value that indicates whether the spatial view is available. When set to false the spatial view is removed from the database, but allows the definition to remain. Setting to true recreates the spatial view in the database.

Default is true.

Creating your first spatial view#

Django Admin#

Logging in as a superuser, navigate to /admin/models/spatialview and click the ADD SPATIAL VIEW + button.

Complete the spatial view details and click the Save button.

SQL Insert#

You can load the spatial view definition into the database using the following SQL:

INSERT INTO
public.spatial_views
(
        spatialviewid       ,
        schema              ,
        slug                ,
        description         ,
        ismixedgeometrytypes,
        attributenodes      ,
        isactive            ,
        geometrynodeid
)
VALUES
(
        '2a578e84-b21a-431d-8de0-59e4d46a88fb',
        'public',
        'artefact',
        'Defines information relating to the character of man made items of heritage significance as identified by the Portable Antiquities Scheme includes individual artefacts, architectural items, artefact assemblages, individual ecofacts and ecofact assemblages, and environmental samples.',
        false,
        '
        [{
            "nodeid": "c30977b0-991e-11ea-ba04-f875a44e0e11",
            "description": "description"
        }, {
            "nodeid": "dd8032af-b494-11ea-8110-f875a44e0e11",
            "description": "primary_reference_number"
        }, {
            "nodeid": "dd8032b1-b494-11ea-a183-f875a44e0e11",
            "description": "legacy_id"
        }, {
            "nodeid": "99cfe72e-381d-11e8-882c-dca90488358a",
            "description": "from_date"
        }, {
            "nodeid": "22e7c550-afc2-11ea-a4a8-f875a44e0e11",
            "description": "repository_owner"
        }, {
            "nodeid": "50edbf22-ab25-11ea-a258-f875a44e0e11",
            "description": "storage_area_name"
        }, {
            "nodeid": "546b1630-3ba4-11eb-9030-f875a44e0e11",
            "description": "artefact_type"
        }, {
            "nodeid": "5b0dfb27-7fe2-11ea-8ac9-f875a44e0e11",
            "description": "artefact_name"
        }, {
            "nodeid": "99cff7f8-381d-11e8-a059-dca90488358a",
            "description": "to_date"
        }, {
            "nodeid": "99cfffd1-381d-11e8-ab51-dca90488358a",
            "description": "cultural_period"
        }
    ]
        ',
        true,
        'f7ccc8b9-f447-11eb-9cb1-a87eeabdefba'
);

Using the spatial views#

To use the spatial views in your client application or datasource for a service, you will need to configure that client to connect to the database using the following credentials:

host: the hostname of the arches database server

port: the port of the arches database server

database: the name of the arches database

user: arches_spatial_views

password: arches_spatial_views

If you are using a client that requires views to geometry type specific (for example ArcGIS), ensure that you have set Ismixedgeometrytype to false.

Important

Currently it is not possible to use the user/groups permissions to restrict access. You will need to manually create specific database users and assign them to the spatial views.

Example Usage#

pg_featureserv and pg_tileserv are lightweight open source feature and vector tile service providers that can be used with these spatial views.

https://access.crunchydata.com/documentation/pg_featureserv/latest/ https://access.crunchydata.com/documentation/pg_tileserv/latest/

Once you have installed the application to run on your machine, open the config file located at:

/path/to/pg_featureserv/config/pg_featureserv.toml

Set the DbConnection setting to the following and restart the application:

DbConnection = "postgresql://arches_spatial_views:arches_spatial_views@<HOSTNAME>:<PORT>/<DBNAME>"