I think the main problem is that the HLR is vendor specific. I have worked on a Siemens D900 and up to today I cannot tell you what OS the HLR was sitting on, and what sort of database Siemens were using. Currently, however, I am using Huawei equipment and the HDU is sitting on a Sun Solaris 10 Server, running an oracle database. The Huawei guys have quite a number of tools that one can put to good use. Because of that, it is difficult for developers to develop a “universal” tool to interface with the HLR.