(1)analysis emphasizes the drawing of pictorial system models to document and validate both existing and/or proposed systems. Ultimately, the system models become the (2)for designing and constructing an improved system. (3)  is such a technique. The emphasis in this technique is process-centered. Systems analysts draw a series of process models called (4).(5) is another such technique that integrates data and process concerns into constructs called objects.

空白（4）处应选择（）

A.PERT

B.DFD

C.ERD

D.UML

LF炉顶技术要求是：水冷炉顶。