CHAP 2 Part 1

data modeling

the process of discovering, analyzing, and scoping data requirements. critical component of data management

data model

you represent and communicate data modeling requirements in a precise form called this

1. relational

2. dimensional

3. object-oriented

4. fact-based

5. time-based

6. NoSQL

six most commonly used schemes in data modeling and design

1. conceptual

2. logical

3. physical

models of these schemes exist at three levels of detail

business drivers

factors or needs that influence an organization’s goals, decisions, and systems

importance of data models

• provide a common vocabulary for data

• document knowledge about an organization’s data and systems

• act as a communication tool during projects

• provide a starting point for customizing, integrating, or replacing applications

formalization

documents data structures and relationships and shows how business rules affect data. definition of data structures

scope definition

defines the boundaries of data, systems, projects, and applications. explain the boundaries for data context and implementation

knowledge retention/documentation

preserves corporate memory/organizational knowledge and provides documentation for future projects

system development lifecycle (SDLC)

data modeling is most frequently performed in the context of systems development and maintenance efforts, knows as the ______

model

a representation of something that exists or a pattern

data model

describes an organization’s data as the organization understands it

category information

data used to classify and assign types

resource information

basic profiles of resources needed

business event information

data created while operational processes are in progress

detail transaction information

often produced through point-of-sale systems

entity

a thing about which organization collects information.

nouns of organization

entity aliases

generic term entity can go by other names. most common is entity-type

entity instances

occurrences or values

entities

in data models. these are depicted as rectangles

entity definition

essential contributors to the business value of any data model

relationship

in relational schemes this term are often used

navigation path

in dimensional schemes this term is often used

edge or link

in NoSQL schemes, terms such as these are used

relationship aliases

can vary based on level of detail

constraints or reference

a relationship at the conceptual and logical levels is called a relationship. but on physical level it may be called other names such as?

cardinality

relationship between two entities. it is represented by symbols

data rules

specified and enforced through cardinality

arity

number of entities in a relationship

unary

also knows as recursive or self-referencing. a relationship that involves only one entity

ternary relationship

arity of three

foreign key

used in physical and sometimes logical relational data modelling

identifier

this is also called a key. a set of one or more attributes that uniquely defined an instance of an entity

simple key

one attribute that uniquely identifies an entity instance

surrogate key

unique identifier for a table

compound key

two or more attributes that uniquely identify an entity instance together

composite key

contains one compound key and at least one other simple or compound key or non-key attribute

super key

set of attributes that uniquely identify an entity instance

candidate key

a minimal set of one or more attributes that identifies the entity instance to which it belongs

business key

one or more attributes that a business professional would use to retrieve a single entity instance

primary key

candidate key that is choses to be the unique identifier for an entity

alternate key

can still be used to find specific entity instances

independent key

one where the primary key contains only attributes that belong to that entity

dependent key

one where the primary key contains at least one attribute from another entity

domain

complete set of possible values that an attribute can be assigned

data type

domains that specify the standard types of data

data format

domains that use patterns including templates and masks, such as are found in postal codes and phone numbers

list

domains that contain a finite set of values

range

domains that allow all values of the same data type. can be open ended (ex: orderdeliverydate)

rule-based

domains defined by the rules that values must comply with in order to be valid (ex: itemprice, itemcost)