Database-driven software, often uses a three-tier methodology with applications being split into three tiers – data storage, processing and presentation. In the data storage and processing tiers, JADE systems are a collection of co-operating servers, called nodes, and multiple nodes may be involved in each tier. Each type of node has a different name and all are capable of manipulating objects and executing business logic. A collection of nodes can be deployed across one or several machines. Database servers handle data storage and can also execute business logic, while application servers handle processing. In a three-tier model, presentation clients provide the user interface. JADE also provides a two-tier client that combines the abilities of an application server and presentation client. Traditionally, these three tiers would be created by combining three programs and having them communicate to form one system. Having the different programs separate like this has many advantages, the main one is that the system becomes scalable, that is, raising the power of the system involves simply adding more nodes.