Conversion from STL to CATIA V6 (3D XML) is not supported yet :(

STL (STereoLithography) is a file format native to the stereolithography CAD software. This file format is supported by many other software packages; it is widely used for rapid prototyping, 3D printing and computer-aided manufacturing. STL files describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. The STL format specifies both ASCII and binary representations. Binary files are more common, since they are more compact.

3DXML is an open-standard proprietary 3D file format developed and supported by Dassault Systemes. 3DXML files are typically created as exports from Dassault Systemes' 3DEXPERIENCE application. The 3DXML file is a zip archive file consisting of a BOM file and one or more 3D representations stored in either XML or binary format. Compact file size allows users to transfer 3D XML quickly and embed it into websites, emails, and various MS Office documents. Therefore, the format is commonly used to integrate 3D data into technical documentation.