谢谢lzh741206. 我在arx的帮助中也找到了这个结论:
You can retrieve extended data for a particular application by specifying its name in a filter list, using the -3 group code. The acedSSGet() function returns entities with extended data registered to the specified name; acedSSGet() does not retrieve individual extended data items (with group codes in the range 1000–2000).