A library provides a straightforward way to share custom report elements and styles across an enterprise. When a library developer saves a customized element in a library, the element is available to any report design that uses the library directly. Because a report design can use multiple libraries, you can separate logical sets of report elements.

Figure 29‑1 shows the structure of a report design that uses libraries. The expanded Libraries item shows the three libraries that the report design uses.

A library is dynamic. When a library developer changes an element in a library, the same changes occur in all report designs that use the library. For example, if the enterprise’s preferred font changes from Arial to Book Antiqua, the library developer makes the changes to styles in a library. When a user generates a report from any design that uses styles from that library, or when a report developer opens or refreshes the design in BIRT Report Designer, the changes take effect. This dynamic behavior ensures that all report elements that derive from a library always use the current styles and properties.

When an enterprise implements a policy of using libraries, the best practice is for every custom element used by more than one report design to derive from a library element. Using an element directly from the palette and customizing it in the same way in multiple designs is error-prone and requires a report developer to update the element in each design if the enterprise’s needs change.