Record-based Logical Models

1. Record-based logical models:
   • Also describe data at the conceptual and view levels.
   • Unlike object-oriented models, are used to
     • Specify overall logical structure of the database, and
     • Provide a higher-level description of the implementation.
   • Named so because the database is structured in fixed-format records of several types.
   • Each record type defines a fixed number of fields, or attributes.
   • Each field is usually of a fixed length (this simplifies the implementation).
   • Record-based models do not include a mechanism for direct representation of code in the database.
   • Separate languages associated with the model are used to express database queries and updates.
   • The three most widely-accepted models are the relational, network, and hierarchical.
   • This course will concentrate on the relational model.
   • The network and hierarchical models are covered in appendices in the text.

• The Relational Model
• The Network Model
• The Hierarchical Model