Namespaces and Extensions
An introduction to "@context" URLs and field names, namespaces (their evolution and deprecation), and extensions.
In the world of linked data on the web, "namespaces" (
"@context") are a collection of "properties" (fields) that have a well defined meaning.
Within the imin data, there are five primary namespaces used, all which are listed in the table below. You can click on each of the namespaces below to see a list of the properties contained within.
imin data is valid JSON-LD, which means that properties will always exist in one of the specified namespaces (
Descriptions and examples of the most commonly used properties from schema.org and SKOS, together with all properties from OpenActive, are included in the OpenActive Developer Documentation. imin and OpenActive Beta namespaces are documented separately at the links above.
When reading a response which contains JSON-LD, you'll should refer to the "
@context" property, which is designed to let you know which namespaces are in use.
Three key things to remember:
- The OpenActive namespace also bundles SKOS and schema.org namespaces inside it:
- So writing
"@context": [ "https://openactive.io/" ]is the same as writing
"@context": [ "https://openactive.io/", "https://schema.org/", "http://www.w3.org/2004/02/skos/core#" ]
- OpenActive, SKOS and schema.org namespaces do not require a prefix when using them:
- So you must write
"name": "Tai chi Class"instead of
"schema:name": "Tai chi Class"
- All other properties always require a prefix:
- You must write
"name": "Tai chi Class",
"imin:fullAddress": "ExampleCo Gym Kingswood, 1 High Street, Kingswood, South Gloucestershire, BS1 4SD"
This example references the namespaces of OpenActive (as noted above, this automatically includes schema.org and SKOS) and imin.
schema.org is a collaborative, community activity with a mission to create, maintain and promote schemas for structured data on the Internet; on web pages, in email messages and beyond. It was founded by Google, Microsoft, Yahoo and Yandex.
The terms of schema.org continue to evolve through lively discussions on their mailing list and GitHub issues. Often properties are added for some specific use case and their potential relationship to other areas of schema.org only becomes clear later. This gives rise to changes in textual definition and property-to-type associations that gradually make schema.org more coherent, without introducing radical changes in meaning. Consumers of schema.org data can generally rely on schema.org term meanings not changing dramatically. However, term definitions often evolve gradually over time to accommodate new usage scenarios or to improve usability. When schema.org properties are occasionally deprecated, they stay in the namespace so that they can still be used and are simply referenced to their replacement property.
The OpenActive W3C Community Group and imin both contribute to discussions within schema.org, however, consensus involves a number of stakeholders and can be time consuming to reach.
Where a schema.org property is explicitly included in the OpenActive Modelling Specification, it follows the OpenActive versioning policy. Where a schema.org property is not included in the OpenActive Modelling Specification, its usage may be subject to change. However, due to schema.org's internal processes and policies, it is highly unlikely to change in name, but somewhat more likely to subtly change in definition.
This specification is not expected to be updated, however, the use of the specification within OpenActive is subject to change in line with the OpenActive versioning policy.
The OpenActive W3C Community Group was established with the objective of facilitating the sharing and use of physical activity data. We very much encourage you to join the conversation and help shape the standards and our future API iterations through this process.
The OpenActive Modelling Specification defines a subset ("profile") of schema.org and SKOS that has been defined for OpenActive use, along with additional properties that feature in the OpenActive namespace.
The OpenActive versioning policy within that specification specifies the use of version numbering to indicate potential for breaking changes: minor versions, e.g. 1.1, 1.2, etc. should be backwards compatible; major versions, e.g. 2.0, 3.0 are likely to include breaking changes. It is estimated that such breaking major version releases will only occur at most annually. imin will strive to align major version releases with OpenActive major version releases, with any deprecated imin API major version maintained for a period in accordance with the imin deprecation policy.
The imin namespace is maintained to facilitate the early stabilisation of properties ahead of their broader adoption and standardisation. imin works as part of the OpenActive W3C Community Group to promote the use cases represented by the properties within this namespace, with the intention of standardising them into the OpenActive Modelling Specification over time (where applicable).
When a property "graduates" from the imin namespace into the OpenActive modelling specification, it will be maintained as a duplicate property for 12 months and deprecated in accordance with the imin deprecation policy.
The OpenActive Beta namespace provides a custom namespace that can be used by publishers experimenting with new properties that are likely to be added to the core specification. It is defined as a convenience to help document properties that are in active testing and review by the community.
Data consumers should not assume that properties in the OpenActive Beta namespace will either be added to the core specification or be included in the namespace over the long term.
Please note that OpenActive Beta namespace properties are not subject to the imin deprecation policy and are subject to change at any time. Therefore, we strongly encourage a defensive data consumption approach. However, if you are considering one of these fields to drive critical production functionality, please get in touch with us at [email protected] and we will work with you to propose your use case to the OpenActive W3C Community Group and move the field into either the OpenActive or imin namespace.
imin data sometimes contains additional namespaces, known as extensions. Data publishers may use these extensions to include additional fields that are not currently being considered as part of the evolving OpenActive standards.
Please note that extension properties are not subject to the imin deprecation policy and are subject to change at any time. Therefore, we strongly encourage a defensive data consumption approach. However, if you are considering one of these fields to drive critical production functionality, please get in touch with us at [email protected] and we will work with you to propose your use case to the OpenActive W3C Community Group and move the field into either the OpenActive or imin namespace.
"name": "Wheel Do It! - Blindside loop (with Betty-Ann)",
"meetingPoint": "Start of Loxley Road just past the bus stop, which is immediately after the pedestrian crossing/traffic lights."
In this example, the
"britishcycling:gpxFile"field is defined by an extension provided by British Cycling, using their custom namespace