Systems Chapter 3

object that exists and wich is distinguishabel frm other objects

-person, place, object

defines a collection of entites that have the same attributes

-Students, radios, cars

single item in this collection

-student with id 123

set of entity instances; subset of entity type

- IE students

property or characteristic of an entity type

cannot be futher divided into smaller components

-city,state,price

can be divided into smaller subparts

• -name: first, last
• -address: street, city, zip

has a single value for an entity instance

-DOB, product weight

may have more than one value for an entity instance

• -Language
• -Sports played

can be determined by analyzing other attributes

• -no need to store them in a database
• -denoted with dashed ellipse
• -age

attribute whose value cannot be derived from the values of other attributes

single attribute or combination of attributes that uniquely identify an individual instance of an entity type

-Student ID

represents the maximum number if unstances of entity B that can be associated with any instance of entity A

the minimum number of instances of entity B that must be associated with each instance of entity A

stores info related to the relationship

an entity type that connects the instances of one or more entity types and contains attributes particular to this assciation

• -allows us to store data from relationship attributes more effectively
• -must be many-to-many binary or ternary

exists independent of other entity types

depends on another entity type

entity type that has one or more distinct subgroups with unique attributes

entity type that shares common attribtes or relationships distinct from other subclasses

the process of defining general entity types from a set of specialized entity types by identifying their common charactersitics from the bottom up

is the process of defining one or more subclasses of a superclass by identifying its distinguishing characteristics from the top down

dictate if each instance (member) of a superclass must participate as an instance of a subclass

an instance of a superclass does not have to be an instance of any of the subclasses

must be an instance of at least one subclass

define whether it's possible for an instance of a superclass to simultaneously be a member of one or more subclasses

if an instance oof a superclass is a member of any subclass, then it cannot be a member of more than one subtype

if an instance of a superclass is a member of any subclass, then it can be a member of more than one subtype

an attribute of a superclass that discriminates a new entry to the superclass into the appropriate subclass

is a hierarchical structure of a superclass and its various subclasses in which each subclass has exactly one superclass