# NMOS Parameter Registers: General Procedures and Criteria

The procedures for updating a parameter register are straightforward.

- Any AMWA member can propose additions or updates.
- In general, deprecation of an entry is to be preferred over removal or substantial amendment.
- The changes should be submitted via a [Pull Request (PR)](https://help.github.com/articles/about-pull-requests/).
- The Pull Request will be reviewed according to the criteria by an [AMWA review team](https://github.com/orgs/AMWA-TV/teams/nmos-parameter-registers-admin).
- If the necessary criteria have been met, the changes will be merged into this repository.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in the defined criteria are to be interpreted as
described in [RFC2119](https://tools.ietf.org/html/rfc2119).
Note that the force of these words is confined to the scope of this repository.

## Example

A typical example of specific criteria is found in the [NMOS Node Service Types](../node-service-types/) parameter register. AMWA IS-04, since v1.1, allows a list of `services` to be advertised on the node resource in the Node API. Each advertised service has a `type` property whose value is a Uniform Resource Name (URN), as well as its `href` property which provides a URL to reach the service. The Node Service Types parameter register provides implementers with the means to discover and disclose service type names (URNs) that are in use.

So, for example, its criteria includes the following statements:

> - Each entry MUST define a unique service type name (which is a URN).
> - Each entry MUST have a short description and include contact information for the proponent(s).
> - Each entry SHOULD provide a link to a specification for the service type, as well as identifying the AMWA IS-04 API Versions for which the entry is applicable.
> - In the case of substantial revision to the service specification, a new service type name MUST be defined. Using versioned names is therefore RECOMMENDED.
> - Additions and updates to this parameter register are to be submitted via a Pull Request (PR) according to the General Procedures and Criteria.

However, modifications to a parameter register may be more closely controlled than this. For example, in the case of the [NMOS Formats](../formats/) parameter register, values are defined only by revisions of AMWA IS-04 itself.

Note: AMWA IS-04 specifies general requirements for the construction and [use of URNs](https://specs.amwa.tv/is-04/releases/v1.3.1/docs/2.1._APIs_-_Common_Keys.html#use-of-urns) in NMOS specifications.
