Description
At the March 7, 2013 meeting of the Reference Information Model Subcommittee, the members discussed the following topic:
1. TOPIC: Refined Guidance for Standards Developers regarding when to use Enumerations v. ValueLists v. Layers:
(a) If there is a reasonable default enumeration for a required element, use the enumeration, but make sure the enumeration includes “UNKNOWN” and “EXTENSION”. Users should only use “UNKNOWN” when they truly do not know the value. Users should use “EXTENSION” when the defaults are so far off the intended meaning that no reasonable default value can be chosen and the local community value is provided in an extension “layer”.
(b) If there isn’t a reasonable default enumeration for an element, use a ValueList. (Here you are expected to use a local ValueList to implement your local community needs.)
(c) Allow for (zero or more) "Layer" elements in your new standard, utilizing the "Layer" element and structure defined in the CommonTypes.
The point of this guidance is to encourage use of default values in the body of the standard and place the local community values in the extensions enabled by the Parameter Name/Value fields (i.e. Layers). This maintains as much interoperability as possible for recipients unfamiliar with the local community values but also provides flexibility for local communities to use their own terminology for those who understand it.
References:
(1) Norm Paulsen's “Environment Canada Layer” document summarizing the “Layers” concept: https://www.oasis-open.org/apps/org/workgroup/emergency-rim/download.php/47099/Environment%20Canada%20Layer(3).doc
(2) Doug Allport's email summarizing “Layers”: https://lists.oasis-open.org/archives/emergency/201206/msg00020.html
(3) Draft “EDXL Extensions” document, summarizing and proposing the use of “Layers” as one of two primary EDXL Extension mechanisms along with ValueLists: https://www.oasis-open.org/apps/org/workgroup/emergency-rim/download.php/47583/EDXL_Extensions_Draft_ver_1.doc
(4) A draft implementation of the DE 2.0 with “Layers” (but not yet revised to comply with the enumerations guidance above and utilizing a draft implementation of a “Layer” element in the common types schema) https://www.oasis-open.org/apps/org/workgroup/emergency-rim/download.php/46846/edxl-de-v2.0-wd10.zip
(5) The DE 2.0 Basics White Paper, revised to include the “Layers” concept (but not yet revised to comply with the enumerations guidance above) https://www.oasis-open.org/apps/org/workgroup/emergency-rim/download.php/46851/DE_2.0_Basics_Draft_ver_10.doc
(6) More information on the “Layers” concept can be found at the website of the Canadian Association for Public Alerting and Notification (http://www.CAPAN.ca )
