I am looking to do some modeling and would like to have a tool that can capture not only a relational model like ERWIN but also allow us to easily port to LDAP as an option.
NOTE: Visio can connect to an existing LDAP server and draw, but does not allow for you to model first and then deploy, unlike its relational capabilities.
I haven't used it in a few years, but Microsoft has an Enterprise Architect version of Visio which allows for data modeling. I would be surprised if Visio didn't also handle LDAP.
The data modeling part probably isn't as extensive as something like ErStudio, but it allows reverse engineering of ODBC data sources and most of the other basic data modeling capabilities (at least it did). They had just started with moving towards data modeling when I used it, so hopefully it's improved since then.