1. About Gentleware and Poseidon for UML

According to Greek mythology, the hero Jason built a ship and named it the Argo. With his comrades, the Argonauts, he left on a quest for the golden fleece. Poseidon, the god of the seas, protected and safely guided their journey.

About 4000 years later, Jason Robbins started an open source project for a UML modeling tool and named it ArgoUML. Many others joined him in this adventurous undertaking, including a group of software developers led by Marko Boger, who was at that time a researcher at the University of Hamburg. Together they greatly advanced the tool. After Jason Robbins shifted his focus to other tasks, the developer group evolved to become leaders of the project. Under their guidance and with their advances, ArgoUML became very popular. They realized the great demand for a tool like ArgoUML, as well as the amount of work necessary to shape it into a professionally usable tool. They finally took the risk of starting a company with the goal of bringing the most usable tool to a broad audience. With respect to their open-source origin, the company is called Gentleware and their tool is called Poseidon for UML.

That is who we are and how our quest started. Today, Poseidon for UML is one of the most popular UML modeling tools on the market. Our special focus is on usability and on making the job of modeling a joy.

1.1. Our Vision

Software development is a creative process. It requires a deep understanding of the problems to be solved, the involved users and stake holders and their requirements, the ability to find the right level of abstraction from reality, and the creativity to shape a software solution. At the heart of software development is the human being. Our goal is to provide tools to increase his creativity and productivity. Tom DeMarco found a word for this: Peopleware. This point of view is engraved in our name. Gentleware is the connection between humans and the software they develop. Our main subject is the development of tools for UML, Java, MDA and XML with a strong focus on usability and high productivity. We also offer training, consulting and individual solutions.

1.2. Innovation

New tools require new ideas. Innovation drives our development. We want to prove this to our customers through improved usability and productivity. Founded with a strong university background, Gentleware maintains our ties to the University of Hamburg. With roots in academia and the community process of open projects, we continuously seek dialog with researchers along with the open source community and users.

1.3. Cooperation

The tools we build are used in a wide range of industries, and the pace of development is high and always increasing. To stay ahead, we cooperate with leading experts and companies. Together with our partners we are building a rich set of development tools and extensions that will fit the needs of our users exactly.

1.4. Contact

We are always very happy to get feedback on our tools and services. If you want to contact us, there are several ways to get in touch.


The easiest way to contact us is via the web form. We offer addresses for different purposes.

General information, feature requests, or suggestions:


Customer support (for premium Editions*):

Please keep in mind that our customer support is available during our normal working hours - Monday through Friday, 9 am to 6 pm Central European Time. Consider checking the forums and the FAQ to answer your question first.


Questions on purchase process, quotes, or volume sales:


* Community Edition users are encouraged to use our forum for support questions.


Web Site

For general discussion we have installed an open forum in which users of Poseidon for UML can freely discuss topics related to our tools. Typically these are questions on how to do something, discussions on what other features would be nice, or comments on what people like or dislike about our tool. Our staff is actively taking part in these discussions, but you might also get a response from other users.

To order our products you can use the online shop, which requires a credit card. If you do not have a credit card or you hesitate to use it over the web, send us an email at sales@gentleware.com.


Our preferred payment method is credit card. However, if you do not have a credit card or you hesitate to use it over the web, you can also send a fax, send email to sales@gentleware.com or call us.

There is a fax order sheet provided on our web site. Begin the order process as usual, then select 'Order by Fax' at the bottom of the Checkout page. Our fax number is +49 40 2442 5331.

Please try to find an answer to your question on our web pages, the FAQ list, or the Poseidon Users Guide.

Regular Mail

To send us mail or to visit us in person, our address is:

Gentleware AG
                        Ludwigstraße 12
20357 Hamburg