The beauty of simplicity
As discussed earlier, the application is designed to be expanded and changed by external partners. When this Partner program was created, a decision was made that partners could only do a good job if the application was completely open for them to add and change. This philosophy is very important to understand when you first start implementing or changing Microsoft Dynamics NAV.
Partners can change all business logic in the application. They can add new fields to tables and create their own tables. The only thing they cannot do is delete fields from the tables in the base application.
As you can see, Microsoft Dynamics NAV is an extremely flexible and open product with a lot of freedom. But with freedom comes responsibilities. In Dynamics NAV, you are responsible for the housekeeping in your system.
Horizontal versus vertical solutions
Because of this open system, partners have created thousands of smaller and larger changes to the system. Some of these changes were bundled into new functional pieces and called "add-ons". These add-ons are often solutions that change Dynamics NAV into a product for a specific industry rather than a generic ERP system. Other add-ons are specific features that can be used in all industries like EDI or Workflow. Microsoft calls the industry specific add-ons verticals and the generic add-ons horizontals.
Open source
Even though Dynamics NAV has an open source for their partners, it does not come fully equipped with a development environment like most developers are used to. It has a customization tool that lets you customize the application like you would customize another ERP system with settings. This customization tool is a basic tool that is nice to work with but misses some development features such as version control and intellisense. This makes it more difficult to keep track of your changes.
