In chapter 2, the content and the description language EXPRESS of STEP are introduced. The structure and format of STEP neutral files are analyzed and studied as.

• 论文第二章详细介绍了STEP标准的内容,以及STEP标准的描述语言EXPRESS,并重点介绍了STEP中性文件的结构和格式,对其作了详细的分析和研究。