Denormalized Data Associations
Many business objects require the representation of data relationships between multiple entities, not only a single entity. The most common such case is the header-detail pattern, where the lines are children with a many-to-one relationship to their parent header. This pattern is often extended to more than two levels; for example, sales order headers, lines, delivery schedules, taxes, and other special charges. Such data can be represented in the form of normalized relational tables, with all associations between the entities embodied in their use of common keys; for example, an order number in the sales order line that references the associated header. It also possible to model relationships in a structured, unnormalized manner, where the child entities are explicitly contained by their respective parents with no need for common key fields.Following common XML usage, QDocs represent parent-child relationships between entities in a structured manner, by making each instance of a child entity a component element inside a parent element. For example, a sales order is represented by a single sales order element that contains zero or more line elements, each of which in turn may contain other types of child elements.