7.5 Business Logic/Middle-Tier

While the pipeline processing system produces data products and files and the user only sees the Java interface, all connections between the two other layers are made by the so called `Business Logic' or middle-tier. The use of a middle-tier has a number of advantages. It isolates the interface from the rest of the system and deals with most of the application business logic and complexity. This has the benefit of making the interface lighter and faster and it also means that a number of changes don't require the users to get a new version of the application. All data transfers between the interface and the middle-tier are compressed which makes the system run faster. This business logic layer is also the way other archives or applications can access the ISO data products and extra files without being required to go through the standard user interface. This has made very easy any inter-operability of IDA in the context of the Virtual Observatories. Another great advantage has been brought by the use of Java in this open 3-tier architecture. The IDA design and code has been re-used to develop other ESA scientific mission archives (e.g. the XMM-Newton Science Archive, first released in April 2002; Arviset et al. 2002, [6]).