As an industry, software design has a long history of projects that run long and over budget. There are three main reasons why this happens. First, project managers may attempt to set schedules and estimate work without a clear understanding of what the project involves. This is especially true when the project involves a desired result unlike any previously attempted by the project team. Second, tasks that should have been a part of the project plan are omitted, generally because of oversight on the part of the project manager.