Whether you are working with objects such as lines, circles and polyline or a symbol table and its records, you need to open the object for read or write. When querying an object you want to open the object for read, but if you are going to make changes to the object you will want to open it for write.
无认你处理是像直径、圆和多段线之类的对象还是符号表以及它的记录，你都必须指定以读或写的方式打开。当查询一个对象时，需要使用读的方式打开对象，但是如果你将要修改对象，就需要以写的方式打开对象。
