Reading Notes - Week of September 24, 2012

Wikipedia Entry: “Database”

• A database is an organized collection of data
• The data is usually organized to model relevant aspects of reality in a way that supports processes requiring the information
• Term database system implies that the data is managed to some level of quality
• Well-known database management systems include Oracle, IBM DB2, Microsoft SQL, Server, Microsoft Access, PostreSQL, MySQL, and SQLite
• A way to classify databases involves the type of their contents (ex. Bibliographic, document-text) or by their application area (ex. Accounting, banking)
• Relational model – applications should search for data by content, rather than by following links
• Relational database systems are the current dominant system
• General purpose DBMS aim to satisfy as many applications as possible, but they are not always the best solution
• Major database usage requirements
• Functional requirements
• Defining the structure of the data
• Manipulating the data
• Protecting the data
• Describing processes that use the data
• Operational requirements
• Availability
• Performance
• Isolation between users
• Recovery from failure and disaster
• Backup and restore
• Data independence
• Current data models
• Relational model
• Entity-relationship model
•  Object model
• object-relational model
• XML as a database model
• Database design is done before building it to meet the needs of end-users within a given application tat the database is intended to support

Wikipedia Entry: “Entity-Relationship Model”

• The entity-relationship model is an abstract way to describe a database
• Starts in a relational database with data stored in tables
• Data in the tables point to data in other tables
• Two levels of the ER Model
• Conceptual data model
• Logical data model
• An entity can be defined as a thing which is recognized as being capable of an independent existence and which can be uniquely identified

Phlonx, " Database Normalization Process"

Database normalization relies on three forms; no repetition of elements or groups of elements, no partial dependencies on a concatenated key, and no dependencies on non-key attributes.