Ch2/w3 Flashcards
(29 cards)
Business rules
- statements that define or contrain
- give businesss structure
- derived from policies/prcodeus
- are automated through dbms and known by end users
4 categories of busienss rules
- terms: these are entities (term is defined as…)
- facts: relationships in an erd, attributed in an erd, or a generalization structure
- constraints: prevent an action from taking place
- derivations: define how knowledge in one form can be transformed into knowledgein another form
characterisitcs of good business rules
declarative, precise, atomic, consistent, expressible, distinct, business oriented
entity legend:
strong
weak a
associative
(Entity types)
rectangle
double rectangle
rounded corners
entity legend attributes
IDENTIFIER / PK
PARTIAL IDENTIIFER
optional
[Derived]
{mv}
compo(os,it,e)
underline
double underline
derived from metadata LIKE # YEARS EMPLOYED
skills
several parts
what is an entity
person place object event or concept
entity type
cllection of entities that share common property
(Strong,weak,…)
enetitiy instancen
one occurence of an entity type (so one data row)
are reports entities?
no
attributre
property or characteiristc of an entity or relationship typecl
classifications of attributes
required v optional
simple v comp
single value v multiv
stored v derived
identifer
associative entity? two types
- attribute on a relationship (like the recntagle box coming off a dashed line)
- assciiative entity (a rounded edges square b/w 2 m:m)
does weak ent have unique ID
no only a partial!
A value that indicates the date or time of a data value is called a:
timestamp
In the following diagram, which is true? item/bom structrure
many to many!!!
An entity type name should be all of the following EXCEPT:
AS SHORT AS POSSIBLE
In an E-R diagram, there are/is ________ business rule(s) for every relationship.
TWO
A good data definition will describe all of the characteristics of a data object EXCEPT:
who can delete data
fact is an association between 2+ terms
TRMSMMSSMMS
The number of entity types that participate in a relationship is called the:
DEGREEEEEEEEEE
The most common types of entities are:
STRONG
which of the following is NOT a agood characterisitc of a data name
RELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEMRELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEMRELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEMRELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEMRELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEMRELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEMRELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEMRELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEM
RELATES TO TECHNICAL CHARACTERISTIC OF THE SYSTEM
WHy data modeling important?
data characterisics are important
data def does not say whp can delete data!!
