Understanding Data Islands

Elements in the Data Presentation design panel are grouped into data islands. Each data island comes from a join tree or unjoined table, but data islands differ from join trees in a number of important ways. Join trees represent the logical model for data in the Domain and data islands represent the business model presented to the users.

Join Tree (or Unjoined Table) Data Island
Each join tree is unique and does not connect to any other join tree. Each data island is unique and does not connect to any other data island.
Structure is organized in tables and fields. Structure is organized in sets and items.
Directly reflects the structure of the tables and columns in the database, along with derived tables, calculated fields, and table and column copies (aliases). Lets you group elements in sets to create a structure that better reflects your business model. You can exclude tables and columns you do not want to expose to the user, without removing them from the original join tree.
Table and column names come from database or internal Domain Designer naming (for calculated fields, derived tables, and table copies). Sets and items can be renamed. Names that appear to users can be defined in localization bundles based on strings assigned in the data island.