Task runners call EvaluateExpression to evaluate a string in the context of the specified object. For example, a task runner can evaluate SQL queries stored in Amazon S3.
POST / HTTP/1.1 Content-Type: application/x-amz-json-1.1 X-Amz-Target: DataPipeline.DescribePipelines Content-Length: 164 Host: datapipeline.us-east-1.amazonaws.com X-Amz-Date: Mon, 12 Nov 2012 17:49:52 GMT Authorization: AuthParams {"pipelineId": "df-08785951KAKJEXAMPLE", "objectId": "Schedule", "expression": "Transform started at #{startDateTime} and finished at #{endDateTime}"} x-amzn-RequestId: 02870eb7-0736-11e2-af6f-6bc7a6be60d9 Content-Type: application/x-amz-json-1.1 Content-Length: 103 Date: Mon, 12 Nov 2012 17:50:53 GMT {"evaluatedExpression": "Transform started at 2012-12-12T00:00:00 and finished at 2012-12-21T18:00:00"}