What characteristics should a good visualization system hold? What kinds of data should it support? What capabilities should it provide? Of course, the answers depend on the particular task and application. For some users a visualization system may be nothing more than a simple image viewer or plotting program. For others it is integrated software dedicated to their personal field of work, such as a computer algebra program or a finite-element simulation system. While in such integrated systems visualization is usually just an add-on, there are also many specialized systems whose primary focus is upon visualization itself.