Data Models

data model

blueprint of the data

what are the 3 main functions of the data model?

• provide structure/organize data

• provide relationships between data

• provide constraints of the data

construct

building block for the data

metadata

description of data’s constructs AND constraints

A spreadsheet containing entities for the mini world of a school best represents _____

constructs

data model operation

actions done on the database

conceptual/high level model

data model similar to the user perception and the mini world; independent of data storage

physical/low level model

data model similar to how data is actually stored; not very friendly for actors on the scene

representational/implementation model

data model showing how computer reads data, but still abstracts some internal processes; often uses tables/illustrations

self describing model

data model using a description of data in a key-value style:

Eg: <Name> Bob </Name>

database schema

static, NON changing description of the structure of data and its constraints

schema diagram

illustration, picture display of the data

schema construct

an element within a database schema

database state

content within a database at any given time

valid state

database state when all constraints are mate

What is the following order of how data is inherited?

data model → database schema → metadata → actual data

3 schema architecture/SPARC model

model that supports multi-view and is used for explaining database organization

internal schema

structure describing how storage works

conceptual schema

structure describing constructs + constraints

external schema

structure describing how the user views the data

logical data independence

changes can occur on the conceptual schema without affecting the external schema

physical data independence

changes can occur on the internal schema without affecting the conceptual schema

changing a schema at the lower level only affects _____

mapping