There is only one file type that uses the .TOPVIW extension:
CAD document created by TopSolid, a CAD design and product data management (PDM) application; stores a CAD drawing exported from TopSolid, but does not include all design information such as the complete models and Bill of Materials (BoM) data; can be opened with the free TopSolid'Viewer program.
TOPVIW files are used for storing drafts of CAD drawings for review and sharing over the Internet. Since TOPVIW files only contain a subset of the design information, they are smaller in size than the original design document. Additionally, this format helps to protect confidential information when sending drafts to external entities.
Updated: January 11, 2011