The Common Alerting Protocol (CAP) is a simple but general format for exchanging all-hazard emergency alerts and public warnings over all kinds of networks.  CAP allows a consistent warning message to be disseminated simultaneously over many different warning systems, thus increasing warning effectiveness while simplifying the warning task.  CAP also facilitates the detection of emerging patterns in local warnings of various kinds, such as might indicate an undetected hazard or hostile act.  And CAP provides a template for effective warning messages based on best practices identified in academic research and real-world experience.

The ASN.1 (see ITU-T Rec X.680) schema in 3.5.3 provides an alternative formulation of the XML schema defined in 3.4.  If the ASN.1 Extended XML Encoding Rules (see ITU-T Rec X.693) are applied to this ASN.1 schema, the permitted XML is identical to that supported by  the XML schema in 3.4.   If the ASN.1 Unaligned Packed Encoding Rules (see ITU-T Rec X.691) are applied to it, the resulting binary encodings are more compact than the corresponding XML encodings.