COMPSCI 122A Lecture Notes - Lecture 1: Courseinfo, Physical Data Model, Conceptual Schema
Document Summary
A very large, integrated collection of data. Usually a model of a real-world enterprise. Entities (students, courses, facebook users) with attributes. Relationships (susan is taking cs 234, susan is a friend of lynn) A software system designed to store, manage, and provide access to one or more databases. Application programs must sometimes stage large datasets between main memory and secondary storage. Must protect data from inconsistency due to multiple concurrent users. Security and access control are also very important. Large carefully tuned data access programs that depend on physical access paths, indexes, etc. A data model is a collection of concepts for describing data. A schema is a description of a particular collection of data, using a given data model. The relational model is the most widely used database model. Many views of one conceptual schema and an underlying physical schema. Views describe how different users see the data. Conceptual schema defines the logical structure of the database.
