To add an user to the existing group

The following two xml work fine when i create
a user and add it to a group.
But when i try to add a new user to the existing group, it creates another group
with the same name.How come iFS accepts
groups with the same name?
Can anyone spare your time to answer this question.
<?xml version = '1.0' standalone = 'yes'?>
<SimpleUser>
<UserName>msmith</UserName>

<Password>ifs</Password>

<DistinguishedNameSuffix>.ambiguity.com</DistinguishedNameSuffix>

<AdminEnabled>false</AdminEnabled>

<HomeFolderRoot>/home</HomeFolderRoot>

<EmailAddressSuffix>@ambiguity.com</EmailAddressSuffix>

</SimpleUser>


<?xml version = '1.0' standalone = 'yes'?>
<DIRECTORYGROUP>
<Name>DemonstrationUsers</Name>

<Members>
<REF reftype='name'>msmith</REF>

</Members>

</DIRECTORYGROUP>

Thanks for your answer in advance