def METHOD_NAME():
    """ Try to guess the platform string according to the operating system, current environment and python interpreter.
    Ganga provides precompiled external packages on a limited set of _default platforms_ as explained in:
    https://twiki.cern.ch/twiki/bin/view/ArdaGrid/GangaSupportedPlatforms
    This function is set only to detect the well-known platform strings as defined by the LCG SPI project and is not meant to be a
    generic platform detection utility. If the platform cannot be guessed a default one is returned. This may or may not work on 
    other systems. In this case you should resolve the external binary dependencies yourself.
    Comments about current implementations:
    SLC5 platform is detected using platform module.
    If it's not SLC5 then:
    We assume that 64 bit python implies the slc4, amd64 system.
    We assume that 32 bit python implies the slc4, ia32 system.
    We ignore IA64 architecture (Opteron) as not frequently used.
    """
    # assume INTEL processors (i386, i686,x64), ignore IA64 architecture
    platf4 = {32: 'slc4_ia32_gcc34', 64: 'slc4_amd64_gcc34'}
    platf5 = {32: 'i686-slc5-gcc43-opt', 64: 'x86_64-slc5-gcc43-opt'}
    # for older python versions use some tricks
    import sys
    bits = sys.maxsize >> 32
    if bits:
        arch = 64
    else:
        arch = 32
    platfstring = platf4
    import platform
    import re
    c = re.compile(r'\S+-redhat-(?P<ver>\S+)-\S+')
    r = c.match(platform.platform())
    if r and r.group('ver').split('.')[0] == '5':
        platfstring = platf5
    return platfstring[arch]