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Table of Contents

2 Introduction

This document presents the current collection of specifications, policy decisions and recommended practices related to the Common Look and Feel (CLF) of public alerts associated with the National Public Alerting System (NPAS) initiative; for alerting authorities, last mile distributors (LMD), and developers of applications that support the distribution of Canadian public alerts to the CLF objectives. Additionally, this document includes a limited number of forward leaning statements relating to efforts to overcome recognized near term challenges associated with achieving CLF objectives.

This document is versioned and will be updated as lessons are learned and advancements are made. Readers are encouraged to ensure they are working with the most current version of NPAS CLF Guidance by checking at

This document was produced with the support of the Centre for Security Science (CSS) Canadian Safety and Security Program (CSSP) at the request of the Federal Provincial Territorial (FPT) Senior Officials Responsible for Emergency Management (SOREM) Public Alerting Working Group, and in consultation with the public-private Common Look and Feel Working Group.

3 Purpose

The purpose of this document is to provide Last Mile Distributors (LMD) and alerting authorities with the guidance they require to support the Common Look and Feel (CLF) of public alerts associated with the NPAS initiative.

The forward leaning statements have a purpose of informing system developers and purchasers that may wish to consider future requirements in their current development and purchases, recognizing that doing so may save them costs in the future.

4 Scope

The CLF guidance provided applies to all media unless specifically noted. Guidance for media not yet supported, such as a wireless public alerting system envisioned for Canada, is not included in this version, but can be expected to be included in future versions.

5 Common Look and Feel

Common Look and Feel (CLF) is an objective that aims to make public alerts more readily recognized by the Canadian public.

Ideally, every member of the public an alert is targeted to would receive the same alert content, the same alert signal, the same presentation format, etc., and while that is not achievable through the variety of distribution mediums, there are practices the NPAS community can follow to reduce the differences between broadcasters and distribution mediums.

CLF is not limited to visual and audible presentation. It also relates to alert repetition, expiry practices, the sequence of audience alert messages presented, and other factors.

6 Terminology

Active Alert:
An alert message which has not expired or been cancelled.
Alberta Emergency Alert:
The province of Alberta's alert aggregation and dissemination system.
Alerting Authority:
An authority, recognized by a government authority, having a responsibility for issuing public alerts.
Alerting Attention Signal:
An audible signal used to capture attention in advance of the presentation of an audience alert message.
Alert Message:
The complete CAP message, which may include multiple audience alert messages. See CAP documentation for further clarification.
Audience Alert Message:
A complete message within a CAP message, that may be distinct from another audience alert message because of the language, alert area, severity, etc., and which is identifiable within the CAP message as a separate <info> block. It may or may not include audio and or other resources.
Broadcasting Distribution Undertaking (BDU):
An undertaking that distributes the signals of broadcasters.
Broadcast Delay:
The time between the CAP alert message being available to a last mile distributor and the audience alert message(s) being presented to the public.
Broadcast Immediately List:
A collection of event types and associated CAP urgency, severity and certainty conditions, that have been identified by the Senior Officials Responsible for Emergency Management as having an imminent or unexpected threat to life, that alerting officials wish to be distributed and presented to the public as soon as possible, even if it means disrupting the programming of last mile distributors.
Broadcast Immediately Alert:
An audience alert message that aligns with the broadcast immediately list.
Canadian Profile of the Common Alerting Protocol (CAP-CP):
A set of rules and references specific to the use of CAP in Canada.
Common Alerting Protocol (CAP):
The international message protocol adopted for use in NPAS. It is an international standard managed by OASIS, the Organization for the Advancement of Structured Information Standards.
CAP Layer:
A specification developed by one or more members of the alerting community that relates to the extension of CAP, in accordance with CAP, for including additional content within a CAP alert message. E.g. A “Broadcast Immediately” element value is defined in the SOREM Layer specification.
CAP Profile:
A specification developed by one or more members of the alerting community that includes additional constraints and rules for CAP users, all of which must be within the bounds of the CAP standard. e.g. Canadian Profile of the Common Alerting Protocol (CAP-CP).
Common Look and Feel (CLF):
The objective of presenting clearly recognizable authoritative audience alert messages to the Canadian public through the diversity of communications media and distributors supporting the NPAS initiative.
Last Mile Distributor (LMD):
A party that presents audience alert messages to the public through one or more media. e.g. Radio, television, search engine provider, SMS text message service, etc.
See CAP Layer.
National Alert Aggregation & Dissemination (NAAD) System:
The CAP alert message aggregation system recognized as the national aggregator for NPAS. Owned and operated by Pelmorex Communications Inc. See
National Public Alerting System (NPAS):
The Canadian federal/provincial/territorial government led public alerting initiative.
Over-the-Air (OTA):
Refers to radio and television broadcast directly to the end user, and not through a BDU.
See CAP Profile.
Senior Officials Responsible for Emergency Management (SOREM) is a forum of Federal/Provincial/Territorial (F/P/T) officials responsible for coordinating a strategy for emergency management in Canada, and for providing guidance and advice on how to enhance emergency management in Canada.  SOREM includes representatives from provincial and territorial emergency management organizations and Public Safety Canada.
SOREM Layer:
A public alerting specification developed and owned by SOREM that is currently limited to identifying an audience alert message as “Broadcast Immediately”.

7 Current State

7.1 Specifications

NPAS participants must work within the requirements of the following specifications. LMDs are not expected to process and distribute alert files which are not in compliance with these specifications.

Common Alerting Protocol (CAP)

The Common Alerting Protocol (CAP) is the message protocol adopted for use in NPAS. It is an international standard managed by OASIS, the Organization for the Advancement of Structured Information Standards. CAP is an international standard that can be found in use in many countries of the world.

Current and past versions of the CAP can be found at

Canadian Profile of the Common Alerting Protocol (CAP-CP)

The Canadian Profile of the Common Alerting Protocol (CAP) was developed to address alerting issues specific to Canada. As an example, CAP-CP requires the inclusion of a Canadian <eventCode>, whereas CAP does not.

Current and past versions of the CAP-CP can be found at

SOREM Layer (Broadcast Immediately)

The SOREM Layer specifies how a CAP-CP audience alert message may be identified as “Broadcast Immediately”. Its presence in a CAP-CP alert message provides LMD's with a simple indication of whether or not a specific audience alert message is associated with an immediate and life threatening situation that warrants an immediate interruption of television, radio and perhaps other programming. The element may reduce the number of programming variables some LMDs may need to work with while also eliminating future programming changes should the list of CAP-CP events and associated element values on the Broadcast Immediately list change in the future. LMD's may only wish to distribute alerts with the SOREM Layer - Broadcast Immediately flag set to “Yes”.

The SOREM Layer may serve other purposes in the future.

The current version of the specification can be found at

7.2 Other Documents

NPAS participants that connect with the National Alert Aggregation and Dissemination (NAAD) System should refer to the most current version of the document titled, National Alert Aggregation and Dissemination System Last Mile Distributor - User Guide, which can be found at An email distribution for updates and notices of this document can be subscribed to.

A document titled Province or Territorial Wide NAAD System Live-to-Air Test Message Policy is forthcoming.

7.3 Guidance

The guidance below applies to all alert messages distributed within the NPAS initiative, and not just those that are “broadcast immediately”. Where guidance is specific to broadcast immediately or a medium, it is noted. To the extent possible, guidance is not repeated. E.g. Official language considerations are not repeated for television; only exceptions are noted.

CAP Message Elements

Official Language Considerations

Alert Text, Audio, Video

Alerting Attention Signal

Duration of Signal: 8 seconds
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Repeat Distribution of Audience Alert Messages

Alert Message Expires, Cancellation

Multiple Alert Audience Messages for the same Distribution Channel

Broadcast Immediately and Effective Time

Multiple <info> Blocks


Broadcast Immediately and Minor Updates


Image Description


Speed of Delivery

Audio Content Considerations

Medium Specific Considerations



Event Location

8 Future State

Stakeholders are encouraged to review the Technical Advisory Note (TAN) produced by the Centre for Security Science (CSS) Public Safety and Security Program (CSSP) at the request of the Federal Provincial Territorial (FPT) Senior Officials Responsible for Emergency Management (SOREM) Public Alerting Working Group, and in consultation with the public-private Common Look and Feel Working Group. Doing so may support a more comprehensive understanding of current constraints and opportunities. Please note this technical document contains technical recommendations only, whereas the current document is the official guidance document.

A key recommendation from the TAN involves the expanded use of CAP <parameter>. The CLF technical advisory team proposed the community use the optional CAP <parameter> element to provide LMDs with a selection of messages of different length, and perhaps specific to a medium, that LMDs could use. This could reduce errors related to composing messages from different CAP <elements>, the truncation of message segments, etc. Additionally, the CAP <parameter> could be used to convey guidance of the alerting authority to the LMDs. e.g. Repeat presentation of alert messages.

The document is available at

9 Credits, Recognition

APPENDIX A - Constraints

Recognized Medium Constraints

Industry Guidance


NPAS Communications Model

The NPAS all channel communications model supports alerting authorities publishing a single alerting information file to a central collection point for distribution through a variety of communications mediums to the public. As illustrated below, there are five key functions within NPAS: Create an alert, aggregate all alerts, share through efficient communications channels, distribute to the public through a variety of media, and receiving the alert through a variety of communications tools and applications.

Key NPAS functions

Key NPAS functions
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Distribution of alert messages is voluntary, and the alert authority has limited influence over the channels the alert message will be distributed through once they are in the public domain.

As with all digital content, alert messages may also be redistributed through multiple communications media by other LMDs and the public. In some cases alerting authorities maintain distribution systems, through which they may distribute the alert messages of other alert authorities.

Alerting authorities should note that all alerts issued in NAAD System and the Alberta Emergency Alert will also be available through the Multi-Agency Situational Awareness Systems – National Information Exchanges (MASAS-X), which serves the Canadian public safety community.

Role of CAP - Message Protocol

The Common Alerting Protocol (CAP), which is an alerting message protocol, plays a key role in the NPAS communications model. CAP defines a single alert message file which includes a collection of one or more audience alert messages (and referenced content) to be presented to the public. Additionally, sufficient information, along with some supplemental guidance, is present for the last mile distributor to determine if the message(s) is relevant for distribution through its medium(s). See illustration.

Role of CAP - Message Protocol
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CAP is replacing the use of email, fax and phone calls between alerting authorities and LMDs, because it supports the automated processing and distribution of alert messages by LMDs, and more efficient and complete distribution to the multitude of LMDs.

Specification Approach

The Common Alerting Protocol is but one of a number of specifications required by the NPAS, and there is a hierarchy to them as illustrated below.

Specification Approach
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The international CAP standard is purposely flexible to the needs of all countries, all systems, and all communities of practice. The Canadian Profile of the CAP (CAP-CP) is a set of rules and managed lists of values that are recommended for all uses of CAP in Canada. This NPAS document provides additional rules and guidance specific to public alerting, but not other uses of CAP-CP. System specific specifications, such as the one for the NAAD System, identify the versions of the higher level documents supported, technical specifications for distribution channels, etc. Each document is to comply with the one above it in the hierarchy. The documents below are more prescriptive that those above.

An objective of this approach is to ensure that the requirements of one community of practice do not negatively impact those of another, while establishing sufficient rules to ensure interoperability between the systems. E.g. Authorities can impose the inclusion of a broadcast immediately flag for public alerts associated with NPAS without burdening issuers of CAP-CP compliant alerts within the Multi-Agency Situational Awareness Systems (MASAS), where it would serve no purpose. NPAS is to also cover end-to-end public alerting system objectives whereas the NAAD System specification can be limited to system specific details like URL's, digital signatures, heartbeat, etc. Additionally, and whereas changes to CAP and CAP-CP may require an engineering change, changes to NPAS and NAAD System specifications are more likely to require only configuration changes.

This approach also supports decision making closest to the requirements, by the people best suited to make such decisions. i.e. The international CAP community does not define system specific requirements for NAAD System, and NAAD System changes do not result in changes for international users of CAP.

CAP “layers” are simple extension mechanisms for adding more nonstandard information to a CAP alert message. Alerting Authorities may define CAP <parameter><valueName>s and <values> in their layers for which they are responsible for formally documenting. Examples of layer information include the SOREM Layer - Broadcast Immediately value, Environment Canada's addition of warning/watch/advisory values for weather alerts, and Natural Resources Canada earthquake magnitude in their CAP alerts. Consistent with Extensible Mark-up Language (XML) practices, alert recipients may simply ignore elements they do not recognize, which means that the addition of “layers” does not impact the integrity of CAP, so long as they are implemented in compliance with CAP accepted practices.

Role of Feeds

Feeds provide an efficient means to deliver complete CAP alerts, or instructions for retrieving complete CAP alerts. E.g. Using an Atom feed to bring attention to CAP alerts available for retrieval. 

Specialized feeds provide a useful means of reducing the number of CAP alerts distributed to, or to be retrieved by, others downstream, such as last mile distributors. For example, with some advanced filtering, a feed could be limited to CAP alerts that are broadcast immediately.

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