Systems Design Chapter 05 Flashcards
Binary Relationships
Relationship between two different types of things - i.e. customer and an order
Unary Relationship (recursive)
Relationship among two things of the same type - such as one person married to another person
Ternary Relationship
Relationship among three different types of things
n-ary Relationship
Relationship among n (any number of) different types of things
Attribute
one piece of specific information about a thing
identifier key
an attribute that uniquely identifies a thing - (primary key in db)
compound attribute
attribute that contains a collection of related attributes
multiplicity
a synonym for cardinality
cardinality
the number of associations that occur among specific things - 1:1 - 1:M - M:M
Data Entities
things about which the system needs to store information in the traditional approach to information systems
Entity Relationship Diagram ERD
The squares with the zero/one to many lines
Associative Entity
A data entity that represents a many-to-many relationship between two other data entities
Generalization/Specialization hierarchies
hierarchies that structure or rank classes from the more general superclass to the more specialized subclasses; sometimes called inheritance hierarchies
inheritance
a concept that allows subclasses to share characteristics of their superclasses
whole-part hierarchies
hierarchies that structure classes according to their components
aggregation
whole-part relationship between an object and its parts
composition
whole-part relationship in which the parts cannot be dissociated from the object
use case
an activity the system performs
user goal technique
an approach for identifying use cases in which an analyst talks to all users to get them to describe their goals in using the system
CRUD technique
Create - Read/Report - Update - Delete an approach in which an analyst looks at each type of data and includes use cases that create the data - read or report on the data - updates the data - delete the data
Elementary business process EBP
A task that is performed by one person - in one place - in response to a business event; it adds measureable business value and leaves the system and its data in a consistent state
Event
an occurrence at a specific time and place that can be described and is worth remembering by the system
Event Decomposition
an analysis technique that focuses on identifying the events to which a system must respond and then determining how the system must respond.
External Event
An event that occurs outside the system - usually initiated by an external agent or actor
Temporal Event
an event that occurs as a result of reaching a point in time
state event
an event that occurs when something happens inside the system that triggers the need for processing. (internal events)i.e. sale of an item results in low stock - inventory reorder must take place
System controls
checks or safety procedures put in place to protect the integrity of the system
perfect technology assumption
the assumption that events should be included during analysis only if the system would be required to respond under perfect conditions.
Event table
a catalog of use cases that lists events in rows and key pieces of information about each event in columns. Event/Trigger/Source/Use Case/Response/Destination
Trigger
a signal that tells the system that an event has occurred - either the arrival of data needing processing or a point in time
Source
an external agent or actor that supplies data to the system
response
an output produced by the system that goes to a destination
destination
an external agent or actor that receives the data from the system
use case description
a description that lists the processing details for a use case
actor
in UML diagrams a person who uses the system
Scenario or use case instance
a unique set of internal activities within a use case that represents a unique path through the use case
Brief Description
short paragraph of the use case
Intermediate Description
Title - main flow & exception conditions
Fully developed description
Contains use case name-scenario-triggering event-brief description-actors-related use cases - stakeholders -preconditions -postconditions -flow of activities - exception conditions.
pre-conditions
conditions that must be true before a use case begins
postconditions
conditions that must be true upon completion of the use case
things
tangible - roles - organizational - devices - sites/locations - incidents/events/or interactions
relationship
a naturally occurring association among specific things such as an order is placed by a customer and an employee works in a department
