MIS 3360

First Normal Form (1NF)

-An attribute value in a relation's row must be a single value from the domain -Each relation must be able to be identified by a primary key -Each row is unique (no rows can be identical) -All relations are in 1NF

Level-0 Diagram

-Represents a system's major processes (functions), data flows, and data stores at a high level of detail -Processes are labeled 1.0, 2.0, ect. -Processes will be decomposed into more primitive (lower-level) DFDs

Second Normal Form (2NF)

-The relation is in 1NF -There are no Partial Dependencies -A Partition Dependency exists: a) If the relation has a composite primary key b) If attributes in the relation depend only on part of the primary key and not entire primary key

Third Normal Form (3NF)

-The relation is in 2NF -There are no Transitive Dependencies -A transitive dependency exists when a non-primary key attribute depends on other non-primary key attributes rather that depending upon the primary key

Logical Database Modeling and Design

1. Develop a logical data model for each known user interface 2. Combine data requirements from all user interface into a single consolidated logical data model (view integration) 3. Translate the conceptual data model into normalized data 4. Compare the consolidated logical data model with the translated model to produce a final logical data model

Rules of Normalization

1. Entries in cells are simple (single value) 2. Entries in a given column are from the same set of values 3. Each row is unique (non-null primary key) 4. Columns can be interchanged/ stored in any sequence 5. Row can interchanged/ stored in any sequence -Normal forms (1NF, 2NF, 3NF)

Properties of Relations

1. Entries in cells are simple (single value) 2. Entries in columns are from the same set of values 3. Each row is unique 4. The sequence of columns con be interchanged without changing the meaning/use of the relation 5. The rows may be interchanged/stored in any sequence

Level-n Diagram

A DFD that is the result of n nested decompositions from a process on a level-0 diagram

Identifier

A candidate key that has been selected as the unique, identifying characteristic for an entity type

Data type

A coding scheme recognized by system software for representing organizational data.

Entity Type

A collection of entities that share common properties or characteristics.

Data flow splitting

A composite data flow at a higher level is split and different parts go to different processes in the lower level DFD. The DFD remains balanced because the same data is involved, but split into two parts.

Branch (Activity Diagram)

A condition whose results provide transitions to different activity paths

Indifferent condition

A condition whose value does not affect which actions are taken for two or more rules. E.g. Hours worked for Salaried Employees

Transitive dependency

A functional dependency between non-key attributes

Supertype

A generic entity type that has a relationship with one or more subtypes

Entity Relationship Diagram (ERD)

A graphical representation of an E-R model.

Object class (class)

A logical grouping of objects that have the same (or similar) attributes, relationships, and behaviors (methods)

Gane and Sarson

A popular symbol set used in data flow diagrams. Processes, data flows, data stores, and external entities all have a unique symbol.

Attribute

A property or characteristic of an entity or relationship type that is of interest to the organization (Ex. EMPLOYEE entity: Employee_ID)

Unary Relationship (Recursive)

A relationship between instances of a one entity type.

Binary Relationship

A relationship between the instances of two entity types

Ternary Relationship

A simultaneous relationship among the instances of three entity types

Homonyms

A single attribute name that is used for two or more different attributes.

Subtype

A subgrouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other subgroupings

Query

Accesses (but does not alter) the state of an object

Activity (Basic Notation)

Action that must take place for a process to be completed

Hashed

Address for each row is determined using an algorithm

Complete

All subclasses have been specified (not the same as total specializtion)

Update

Alter the state of an object

Foreign Key

An FK is an attribute that appears as a non-primary key attribute in one relation and as a primary key attribute (or part of a primary key) in another relation

Decision Tables

An analysis model that specifies complex business rules or logic concisely in an easy-to-read tabular format, specifying all of the possible conditions and actions that need to be accounted for in business rules.

Extend relationship

An association between two use cases where one adds new behaviors or actions to the other

Include relationship

An association between two use cases where one use case uses the functionality contained in the other

Required attribute

An attribute of an entity that must have a value for each entity instance.

Composite attribute

An attribute that has meaningful component parts (attributes).

Optional attribute

An attribute that may not have a value for every entity (or relationship) instance with which it is associated.

Derived attribute

An attribute whose values can be calculated from related attribute values

Overlap rule (letter o)

An entity instance can simultaneously be a member of two (or more) subtypes

Partial specialization (single line

An entity instance of the supertype does not have to belong to any subtype, and may or may not be an instance of one of the subtypes

Weak Entity

An entity that displays existence dependence and inherits the primary key of its parent entity. For example, a DEPENDENT requires the existence of an EMPLOYEE.

Strong Entity

An entity that is existence-independent, that is, it can exist apart from all of its related entities. Also called a regular entity

Functional Decomposition

An iterative process of breaking the description of a system down into finer and finer detail, which creates a set of charts in which one process on a given chart is explained in greater detail on another chart.

File organization

Arranging related records in secondary memory for storage, retrieval, and updates

Trigger

Assertion/rule that governs validity of

Candidate Key

Attribute (or combination of attributes) that uniquely identifies each instance of an entity type

Determinant

Attribute the determines other attributes

Primary Key

Attribute whose value is unique across all occurrences of a relation

Activity (Activity Diagram)

Behavior that an object carries out while in a particular state

Synchronous message

Caller has to wait for the receiving object to finish executing the called operation before it can resume execution itself

Partitioning

Capability to split a table into separate sections

Concrete class

Class that can have direct instances

Constructor

Creates a new instance of a class

Physical database design

Database tables

Gateway

Decision point

Abstract class

Defines the form/protocol of the operation, but not its implementation

Use Cases

Depiction of a system's behavior/functionality under various conditions as the system responds to requests from users

Connection

Depicts a usage relationship between an actor and use case

Use Case Diagram

Depicts system behavior along with the key actors that interact with the system

Data Flow Diagram (DFD)

Depicts the movement of data between external entities and the processes and data stores within a system

Disjoint

Descendant may not from more than one subclass

Overlapping

Descendent may be from more than one of the subclasses

Entity Relationship Modeling

Detailed, logical representation of the entities, associations and data elements for an organization or business area

Total specialization (double line)

Each entity instance of the supertype must be a member of some subtype in a relationship

Referential Integrity Constraint

Each foreign key value must match a primary key value in another relation, OR the foreign key

Full functional dependency

Each non-primary key attribute is identified by the WHOLE Primary key

Join (Activity Diagram)

End of parallel activities

Object

Entity with a well-denied role in an application domain with state, behavior, and identity characteristics (single occurrence of a class)

Pointer

Field of data that can be used to locate a related field/row of data

Stored data structure

Grouping logical database model attributes into physical records

Disjoint rule (letter d)

If an entity instance of the supertype is a member of one subtype, it cannot simultaneously be a member of any other subtype

System boundary

Includes all the relevant use cases: -A boundary is the dividing line between the system and its environment -Use cases are within the boundary -Actors are outside of the boundary

Multivalued attribute

May take on more than one value for a given entity instance

Message (Sequence Diagram)

Means by which objects communicate with each other

Business Process Modeling

Modeling the standard methods for accomplishing a particular task necessary for an organization to function

Relation

Named, 2-dimensional tables of data -Set of named columns (attributes) -Arbitrary number of unnamed rows (records) -Primary key (identifier)

Logical database design

Normalized relation

Triggering Operations

Other business rules that protect the validity of attribute values

Data integrity controls

Preventive measures that improve data quality -Default Value -Range Control -Referential integrity -Null value

Normalization

Process of converting complex data structures into data structures characterized by simplicity, non-redundancy, and minimal maintenance

Level

Refers to degree of detail in the use case description (1-Summary... 5-Detail)

Objects (Sequence Diagram)

Represented by boxes at tip of diagram

Sequential

Rows in a file are stored in sequence according to a primary key value

Referential Integrity Constraint

Rules governing relationships between entity types

Polymorphism

Same operation may apply to two of more classes in different ways

Storage media

Selecting media and structures for data storage to make access more efficient

Asynchronous message

Sender does not have to wait for the recipient to handle the message

Domain

Set of all data types and values that attribute can assume(Constraints on valid values for attributes)

Relational Database

Set of tables that are related by foreign keys referencing primary keys

Activity Diagram

Show the conditional logic for the sequence of system activities needed to accomplish a business process

Flow

Shows the sequence of action in a process

Class diagram

Shows the static structure of an object-oriented model: the object classes, their internal structure, and the relationships in which they participate

Discriminator

Shows which property of object class is being abstracted

Entity instance

Single occurrence of an entity type

Field

Smallest unit of named application data recognized by system software

Incomplete

Some additional subclasses are not the model

Business rules

Specifications that preserve the integrity of the logical data model

Rules

Specifies which actions are to be followed for a set of conditions

Functional Dependency (FD)

Specify a relationship between attributes in a relation(A->B, Emp_ID->Name)

Data type

Storage format for each attribute from the logical data model

Action Stubs

The actions that result for a given set of conditions

Fork (Activity Diagram)

The beginning of parallel activities

Conditional Stubs

The conditions relevant to a decision

Cardinality

The number of entity instances associated with another entity

Degree

The number of entity types that participate in a relationship.

Normalization

The process of converting complex data structures into simple, stable data structures -Normalization provides a stepwise approach to designing a relation that is guaranteed to be free of data redundancies using Normal Forms

Gap analysis

The process of discovering discrepancies between two or more sets of DFDs or discrepancies within a single DFD

Indexed

The rows are stored either sequentially or non-sequentially, and an index is created that allows software to locate individual rows

Lifeline (Sequence Diagram)

The time during which an object exists

Activation (Sequence Diagram)

Time period during which an object performs an operation

Simple message

Transfers control from the sender to the recipient without describing the details of the communication

Event (Basic Notation)

Trigger that initiates the start of a process

Synonyms

Two different names used for the same attribute

Abstract use case

Type of use case that is initiated by another use case instead of by an actor

Entity Integrity

Unique, non-null identifiers

Sequence Diagram

Used to show interactions among objects for a particular use case

Merge (Activity Diagram)

Where different paths converge

Swimlanes (Activity Diagram)

columns representing different organizational units of the system

Context Diagram

overview of an organizational system that shows the system boundaries, external entities that interact with the system, and the major information flows between the entities and the system(Always contain 1 process and no data stores)

Level-1 Diagram

results from decomposition of Level-0 diagram