RCAP - Common Alerting Protocol for Ruby

Overview

The Common Alerting Protocol is a lightweight standard to facilitate the distribution of alerting data. RCAP is an implementation of the CAP document protocol in Ruby. It allows for the creation of RCAP messages from Ruby applications and the parsing of external messages.

RCAP currently supports CAP 1.0, 1.1 and 1.2.

Version

1.3.0

Dependencies

RCAP depends on the following gems

RCAP uses the REXML API, included in Ruby, to parse and generate XML.

Installation

RCAP is distributed as a Ruby gem and is available from Rubygems.org. From the command line you can install it with the gem command:

$ gem install rcap

The gem is also available for download and manual installation at www.aimred.com/gems.

Web resources

The RCAP project page can be found at http://www.aimred.com/projects/rcap
The RCAP API docs can be found at http://www.aimred.com/projects/rcap/api
A public git repository can be found at git://github.com/farrel/RCAP.git

Usage

To include RCAP into your application add the following require

require 'rcap'

All RCAP classes reside in the RCAP namespace but including the RCAP module makes the classes available at the top level without the RCAP prefix.

include RCAP:CAP_1_2 # Include RCAP:CAP_1_2 module into namespace
alert = Alert.new

Creating an Alert

alert = Alert.new( sender:   'cape_town_disaster_relief@capetown.municipal.za',
                   status:   Alert::STATUS_ACTUAL,
                   msg_type: Alert::MSG_TYPE_ALERT,
                   scope:    Alert::SCOPE_PUBLIC )

alert.add_info( event:       'Liquid Petroleoum Tanker Fire',
                language:    'en-ZA',
                categories:  [ Info::CATEGORY_TRANSPORT, Info::CATEGORY_FIRE ],
                urgency:     Info::URGENCY_IMMEDIATE,
                severity:    Info::SEVERITY_SEVERE,
                certainty:   Info::CERTAINTY_OBSERVED,
                headline:    'LIQUID PETROLEOUM TANKER FIRE ON N2 INCOMING FREEWAY',
                description: 'A liquid petroleoum tanker has caught fire on the N2 incoming freeway 1km
                             after the R300 interchange.  Municipal fire fighting crews have been dispatched.
                             Traffic control officers are on the scene and have diverted traffic onto
                             alternate routes.' )

alert.infos.first.add_area( area_desc: 'N2 Highway/R300 Interchange' ).add_geocode( name: 'Intersection', value: 'N2-15' )

# Accessing attributes
alert.status                           # "Actual"
alert.infos[0].language                # "en-ZA"
alert.infos[0].categories.join( ', ' ) # "Transport, Fire"
alert.infos[0].areas[0]                # "N2 Highway/R300 Interchange"

Parsing an Alert From An External Source

RCAP can parse a CAP alert from a varierty of file formats. Besides the standard XML representation, YAML and JSON support is also included.

To ensure the correct RCAP Alert object (RCAP::CAP_1_1::Alert or RCAP::CAP_1_2::Alert) is returned from an external source, a number of factories are defined in the RCAP::Alert module. If the version of the document to be parsed can not be ascertained a CAP 1.2 document will be assumed.

From XML

RCAP allows for the parsing of a CAP XML string

alert = RCAP::Alert.from_xml( xml_string )

From YAML

Alert messgaes can be read in from text files containing data formatted in YAML as generated by Alert#to_yaml.

alert = RCAP::Alert.from_yaml( yaml_string )

From JSON

An Alert can also be initialised from a JSON string produced by Alert#to_json

alert = RCAP::Alert.from_json( json_string )

Validating an alert

The RCAP API aims to codify as many of the rules of the CAP XML format into validation rules that can be checked using the Assistance API. The following Info object has two attributes ('severity' and 'certainty') set to incorrect values.

info = Info.new( event:      'Liquid Petroleoum Tanker Fire',
                 language:   'en-ZA',
                 categories: [ Info::CATEGORY_TRANSPORT, Info::CATEGORY_FIRE ],
                 urgency:    Info::URGENCY_IMMEDIATE,
                 severity:   nil,                     # Severity is not assigned
                 certainty:  'Incorrect Certainty' )  # Certainty is assigned an incorrect value

puts "Is info valid: #{ info.valid? }"
info.errors.full_messages.each{ |message| puts "Error: #{ message }" }

Will produce the following output:

Is info valid: false
Error: severity is not present
Error: certainty can only be assigned the following values: Observed, Likely, Possible, Unlikely, Unknown

All RCAP classes include the Validation module.

A full spec suite using RSpec} was used to test the validations and currently numbers over 1000 tests.

Exporting an Alert

To XML

Using the alert message created above

puts alert.to_xml # Print out CAP XML message

Will print the following CAP XML

<?xml version='1.0'?>
<alert xmlns='urn:oasis:names:tc:emergency:cap:1.2'>
  <identifier>494207a7-f86b-4060-8318-a4b2a3ce565e</identifier>
  <sender>cape_town_disaster_relief@capetown.municipal.za</sender>
  <sent>2009-10-26T21:04:51+02:00</sent>
  <status>Actual</status>
  <msgType>Alert</msgType>
  <scope>Public</scope>
  <info>
    <language>en-ZA</language>
    <category>Transport</category>
    <category>Fire</category>
    <event>Liquid Petroleoum Tanker Fire</event>
    <urgency>Immediate</urgency>
    <severity>Severe</severity>
    <certainty>Observed</certainty>
    <headline>LIQUID PETROLEOUM TANKER FIRE ON N2 INCOMING FREEWAY</headline>
    <description>
      A liquid petroleoum tanker has caught fire on the N2 incoming freeway 1km
      after the R300 interchange. Municipal fire fighting crews have been
      dispatched. Traffic control officers are on the scene and have diverted
      traffic onto alternate routes.
    </description>
  </info>
</alert>

To YAML

YAML is a plain text serialization format designed to be easily readable and editable by both human and machine. RCAP has custom YAML generation and parsing methods to produce a YAML document that is as human friendly as possible. The following code

alert.to_yaml

will produce the following YAML document

---
CAP Version: 1.2
Identifier: 2a1ba96d-16e4-4f52-85ea-0258c1440bd5
Sender: cape_town_disaster_relief@capetown.municipal.za
Sent: 2009-11-19T02:41:29+02:00
Status: Actual
Message Type: Alert
Scope: Public
Information:
- Language: en-ZA
  Categories: [Transport, Fire]
  Event: Liquid Petroleoum Tanker Fire
  Urgency: Immediate
  Severity: Severe
  Certainty: Observed
  Headline: LIQUID PETROLEOUM TANKER FIRE ON N2 INCOMING FREEWAY
  Description: |-
    A liquid petroleoum tanker has caught fire on the N2 incoming freeway 1km
    after the R300 interchange.  Municipal fire fighting crews have been dispatched.
    Traffic control officers are on the scene and have diverted traffic onto
    alternate routes.

Note: If you use Ruby 1.8 the order of the attributes is jumbled due to hashes being unorderd (Ruby 1.9 implements ordered hashes). This does not affect the ability to parse documents generated from RCAP::Alert#to_yaml, it just makes things the output slightly messy.

To JSON

JSON is a text serialization format that can be easily loaded in a JavaScript environment.

alert.to_json

will produce the following JSON string

{"cap_version":"1.2",
 "identifier":"0eb97e40-195b-437b-9a01-55fe89691def",
 "sender":"cape_town_disaster_relief@capetown.municipal.za",
 "sent":"2011-03-04T15:58:01+02:00",
 "status":"Actual",
 "msg_type":"Alert",
 "scope":"Public",
 "infos":[
   {"language":"en-ZA",
    "categories":["Transport","Fire"],
    "event":"Liquid Petroleoum Tanker Fire",
    "urgency":"Immediate",
    "severity":"Severe",
    "certainty":"Observed",
    "headline":"LIQUID PETROLEOUM TANKER FIRE ON N2 INCOMING FREEWAY",
    "description":"A liquid petroleoum tanker has caught fire on the N2 incoming freeway 1km
                   after the R300 interchange. Municipal fire fighting crews have been dispatched.
                   Traffic control officers are on the scene and have diverted traffic onto \nalternate routes."}]}

DateTime and Time

It is highly recommended that when dealing with date and time fields (onset, expires etc) that the DateTime class is used to ensure the correct formatting of dates. The Time class can be used when generating a CAP alert XML message however any CAP alert that is parsed from an external XML source will use DateTime by default.

Authors

Farrel Lifson - farrel.lifson@aimred.com - http://www.aimred.com

Contributors

Earle Clubb - http://github.com/eclubb

Change Log

CHANGELOG

License

RCAP is released under the BSD License.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY AIMRED CC ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL AIMRED CC OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are those of the authors and should not be interpreted as representing official policies, either expressed or implied, of AIMRED CC.