The contents of an alert message are contained in a set of prescribed sub-
elements contained in the <alert> and <info> blocks. Some of these elements
are required by CAP v1.1; others are optional or contingent on other factors.
For example, the <alert> element must contain a set of prescribed sub-ele-
ments containing content that identifies the sender of the message, the type
of message, and the time and date (time/date stamp) for the message.
14.4.2 CaP Profile Document
Whereas the CAP standard establishes the basic architecture of an alerting
message through its prescribed elements and sub-elements, many of the
actual values and usage conventions must be user-defined. As such, any
implementation of CAP requires some further specification in terms of how
various sub-elements (e.g., message ID) will be populated by an alerting sys-
tem during message creation. Such specification may lead to the creation
of a CAP profile document (see, for example, Common Alerting Protocol
Canadian Profile (v1.1) ).
The CAP profile document is defined as a set of additional requirements
within the scope and conformation of basic CAP specification. These con-
straints establish rules and conventions to ensure that local requirements
and alerting policies, as well as particular data requirements, are translated
into a fully validated CAP message format. A CAP profile therefore defines
a specific instantiation while ensuring that messages created and distrib-
uted by that instantiation remain CAP compliant and will “make at least
basic sense to recipients that are unaware of the profile restrictions” (CAP
Cookbook 2009). This last point is especially important to facilitate infor-
mation sharing and growth of an alerting system across organizational and
14.4.3 CaP implementation for the rTbP initiative
Within the RTBP initiative, alerts will be created using a message broker
based on CAP v1.1. Message contents are contained in a CAP envelope that
is transported using one or more transport protocols appropriate to the mes-
sage distribution subsystem and end-user devices. Later stages of the RTBP
project may include the addition of an EDXL envelope, which adds an addi-
tional layer of information using the EDXL Distribution Element. Table 14.1
shows the relationship between three types of end-user devices (long text,
short text, and voice), CAP elements, and the contents of an alert message.
The required alert attributes listed in the second column are described in
more detail in the following section.