In network databases, a record type can have multiple owners. In the example below, orders are owned by both customers and products, reflecting their natural relationship in business.
Relational databases do not link records together physically, but the design of the records must provide a common field, such as account number, to allow for matching. Often, the fields used for matching are indexed in order to speed up the process. In the following example, customers, orders and products are linked by comparing data fields and/or indexes when information from more than one record type is needed. This method is more flexible for ad hoc inquiries. Many hierarchical and network DBMSs also provide this capability.
Object Databases Certain information systems may have complex data structures not easily modeled by traditional data structures. An "object database" can be employed when hierarchical, network and relational structures are too restrictive. Object databases can easily handle many-to-many relationships.
Intelligent Databases All DBMSs provide some data validation; for example, they can reject invalid dates or alphabetic data entered into money fields. But most validation is left up to the application programs. Intelligent databases provide more validation; for example, table lookups can reject bad spelling or coding of items. Common algorithms can also be used such as one that computes sales tax for an order based on zip code. When validation is left up to each application program, one program could allow an item to be entered while another program rejects it. Data integrity is better served when data validation is done in only one place. Mainframe DBMSs were the first to become intelligent, and all the others followed suit.
DBMS and OS Interaction
This diagram shows the interaction between the DBMS with other system and application software running in memory.
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