chapter 2 Flashcards
(31 cards)
what is a conceptual model
- -> captures the functional and informational needs of the business
- -> it is based on current needs but may reflect future needs
- -> addresses the needs of the business but does not address its implementation
- -> result of completing the data modelling process
what does a conceptual model identify
- -> important entities
- -> relationship among entities
what does a conceptual model not specify
- -> attributes
- -> unique identifiers
why is a conceptual model important for a business
- -> describes exactly the information needs for the business
- -> facilitates discussion
- -> prevents mistakes and understandings
- -> forms important ideal system documentation
- -> forms a sound basis for physical database design
- -> documents the process of the business
- -> takes into account the regulations and laws governing this industry
what is a logical model
- -> includes all entities and relationships among them
- -> is called an entity relationship model (ERM)
- -> is illustrated in an ERD
- -> specifies all attributes and UIDs for each entity
- -> determines attribute optionality
- -> determines relationship optionality and cardinality
what is a physical model
- -> extension of a logical data model
- -> defines table definition, data types, and precision
- -> identifies views, indexes and other database objects - -> describes how the objects should be implemented in specific database
- -> shows all table structures including columns, primary key, and foreign keys
what is data modelling
–> process of capturing the important concepts and rules that shape a business and depicting them visually on a diagram.
data models show users the ___________ that their physical models will contain
data
a conceptual model is not concerned with how the _________ will be implemented
physical model
our technology rich world produces vast quantities of facts in need of ___________
structure and order
why is it important to learn about entities
They are things about which we store dat a
why is it important to learn about attributes
- -> provide more specific information about the entity
- -> attributes help you distinguish between one instance and another by providing greater detail for the entity
what is the example of attributes
–> when you are placing a restaurant order then you have to list the individual food items ordered to calculate the total bill.
what is the purpose of unique identifiers
distinguish one instance of an entity from anothe r
what is an example of unique identifier
–> in a classroom, you need to distinguish between one student and another
what is an entity
- -> something of significance to the business about which data must be known
- -> a name for a set of similar things that you can list
- -> usually a noun
- -> entities have an instance
what is an instance
–> an instance is a single occurrence of an entity
give 3 examples of entities and instances
entities are
- -> person
- -> job
- -> animal
instances are
- -> steve jobs, elon musk, sheldon cooper
- -> engineer, doctor, lawyer
- -> tiger, shark, monkey
entities can be _______, ________ and __________
tangible -> person, product
intangible -> skill level
event -> concert
what is an attribute
- -> represents something of significance to the business
- -> describes an entity
- -> quantify an entity
- -> qualify an entity
- -> classify an entity
- -> specify an entity
–> AN ATTRIBUTE HAS A SINGLE VALUE
an attribute has values called ____________
data types/formats
–> EACH ATTRIBUTE STORES ONE PIECE OF DATA OF ONE SPECIFIC DATA TYPE
what are volatile attributes
some attributes have values that constantly change
what are non volatile attributes
Attributes which do not change
if given a choice which attribute should you select
non volatile attribute
