Very often, CGM users try to use generic CGM files in WebCGM viewers without success. Here is an overview what you should watch out for.

Generic CGM files without graphical objects
Most commercially available viewers let you display such files without problems.

CGM files with graphical objects (grobjects)
An ATA GREXCHANGE file is not a WebCGM, although the definition of the graphical objects is almost identical in both profiles. The major difference is that WebCGM allows you to specify a link, and ATA not.

CGM files with private application structures
Files that contain private objects like the ones that can be defined in an IsoDraw Graphics DTD can usually be displayed in viewers of that vendor only. IsoView can handle all aspects of objects defined in an IsoDraw Graphic DTD. It is also able to read other vendors object definitions and string attributes.

IsoView WebCGM is restricted to display only true WebCGM files. It will reject all other kinds of CGM files.