I assessed both products (Together/J 3.0 and Rose 98i actually) in detail about a year ago now. They are both UML based OOA/D
CASE tools. They do compare fairly closely, but depending on your work environment, one may stand out better than the other. Here are some high level pros/cons of both products, circa Q4 1999:
1. Excellent support for class and sequence diagrams. I also
liked the support for methods or variables being able to
be defined as having class or instance scope.
2. Forward/reverse engineering to Java source was very
nearly a foolproof endeavor. Forward engineering happens
as class design takes place, so a no brainer there. You
need only point to a directory and the tool can reverse
engineer a pre-existing source code baseline. Changes to
code (created during class design) that happen outside of
Together/J are reflected when the tool comes back on line.
Also, when a pre-existing source code baseline is reverse
engineered, the classes in a package are properly laid out
to minimize confusion when rendering relationships between
the classes (minimized line crossing).
3. I really liked that fact that any documentation that was
provided for a given class, method, variable/field,
parameter, exception, or return value, was forward
engineered into the java source code within a javadoc
compliant comment block.
4. It does support team development, but because of its file
structure for housing diagram details, makes it a bit
cumbersome to use in a team environment. Instead of just
checking out a package to work on, the designer would need
to check out the package and the class level files desired
to be modified. Not a big deal, but not convenient.
1. Very convenient to use in a team environment. To checkout
a UML package to work on, you simply create a "unit"
comprising the package of interest, and everything in that
package is available for modification.
2. Support for class and sequence diagrams could be better. No
way to specify that a given method has class scope, other
than to preface the method name with "static".
3. Forward and reverse engineering made your day fairly
frustrating and unpleasant.
For general UML understanding, Martin Fowler's book, "UML Distilled" is very good and concise. The second edition of the book came out in August of 1999 I believe, so there may be a newer edition available now.
Only info I know of regarding TogetherSoft is their website, www.togethersoft.com.