2. Database System Concepts and Architecture Flashcards
client module
runs on user workstation or personal computer (handles user interaction and provides user-friendly interfaces)
server module
Handles data storage, access, search etc.
client/server DBMS architecture
system functionality is distributed between two types of modules
data model
a collection of concepts that can be used to describe the structure of a database
high-level / conceptual data model
close to user perception of data
low-level / physical data model
describe details of how data is stored
entity
a real-world object or concept that is described in the database
representational / implementation data models
provide concepts that may be understood by end users but that are not too far removed from the way data is organized within the computer
attribute
some property of interest that further describes an entity
relationship
an association among two or more entities
access path
structure that makes the search for particular database records efficient
object data models
higher-level implementation data model that are closer to conceptual data models
database schema
description of a database (during design, does not change often)
schema diagram
displayed schema with schema constructs (no instances)
database state or snapshot / current set of occurrences or instances
the data in the database at a particular moment in time
valid state
a state that satisfies the structure and constraints specified in the schema
meta-data
descriptions of the schema constructs and constraints
intension of a database
the database schema
extension of schema
database state
three-schame architecture (goal)
separate user applications and physical database
internal level / internal schema
describes physical structure of database
conceptual level / conceptual schema
describes structure of whole database for community of users
external or view level
includes number of external schemas or user views
mappings
process of transforming requests and results between levels
