1.一个package包含一个control flow并且一个或多个data flow.
(这个项目叫做 Integration services project,提供了三种不同类型的control flow 元件)
1.1 containers(provide structures in packages)
1.2 tasks(provide functionality)
1.3 precedence constraints (connect the executables, containers, and tasks into an ordered control flow) 优先限制