Currently, CloudStack EC2 API layer implements both SOAP interface and Query API. But the Query API support is not well tested. This feature aims to have Query API with the exact fidelity as the current SOAP implementation. Please find the draft of the functional spec here - https://cwiki.apache.org/confluence/display/CLOUDSTACK/EC2++-+Functional+Spec+for+Query+API+support.
Please review and provide your feedback. Thank you, Likitha
