Datasheet

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Chapter 1 ✦ The Information Architecture Principle
Figure 1-2: The generic pattern is an RDBMS physical schema
that is sometimes employed to mimic an OO DBMS.
The class entity drives the database schema. The class entity includes a reflexive relation-
ship to support object class inheritance. As with a hierarchical structure or organizational
chart, this relationship permits each object class to have multiple subclasses, and each
object class to have one base class. The
property entity is a secondary entity to the object
entity and enables each object class to contain multiple properties. An object is a specific
instance of an object class. As such, it needs to have its own specific values for every prop-
erty of its object class and all inherited object classes.
Although the result can be impressive, many complications are involved in this process.
Many-to-many relationships, which exist in real life, are simulated within object-oriented
databases by means of object collections. Properties must meet data-type and validation
rules, which must be simulated by the data schema, rather than by SQL Server’s built-in data-
type and validation rules.
Data Integrity
The ability to ensure that persisted data can be retrieved without error is central to the
Information Architecture Principle, and the first problem tackled by the database world.
Without data integrity, a query’s answer cannot be guaranteed to be correct, consequently,
there’s not much point in availability or performance.
As data is essentially entities and attributes, data integrity consists of entity integrity and
domain integrity, which includes referential integrity and user-defined integrity. Transactional
integrity, which deals with how data is written and retrieved, is defined by the ACID princi-
ples (atomicity, consistency, isolation, and durability), discussed in a later section, transac-
tional faults, and isolation levels.
attribute/
property
subclasses
class
object
value
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