It really all depends on what you are trying to do in the browser. When the ACIS file is converted to a SC model not all the data in the original CAD file is mantained, in particular only a subset of the geometry/brep information which is relevant to performing precise measurement (e.g. the length of aline, the diameter of a circle, etc) is written to the SC model and you are right, the full data is also not available via the XML file.
If you need more information out of the CAD file (e.g. the nurbs definition of a curve, etc) or need more detailed topolgogy information then you would have to pull this information out of the model on the server. One way to do this is to generate a PRC file that you would then load into HOOPS Exchange server-side to query the relevant information (either during conversion or interactively when loading the SC model into the viewer). You can find more information about this (fairly advanced) workflow here:
[HOOPS Exchange to StreamCache Mapping (Beta)]
I’m still curious to find out more about your application and what you are trying to build with the HOOPS Web Platform.