Data and functional modeling

Data and Functional Modeling

Saranya.V
AP/CSE,
Sri Vidya College of Engineering & Technology,
Virudhunagar

Introduction

• Data Modeling in software Engineering is the process
of creating a data model by applying formal data
model descriptions using data modeling techniques.

• Used to define and analyze data requirements needed
to support the business processes of an organization.

• Data requirements are recorded as a Conceptual
Model.

• Implementation of Conceptual model is called as
logical model.

Uses of Data Modeling

• Manage data as a resource.

• For the integration of information systems

• For designing databases, data warehouses and
data repositories.

Tasks in Data Modeling
• Application developer should know the fundamentals of data
modeling in order to work effectively with Database
Administrator(DBA).
• Identify entity types

• Identify attributes

• Apply naming conventions

• Identify relationships

• Assign keys

• Apply data model patterns

• Normalize to reduce data redundancy

• Denormalize to improve performance.

Entity/Relationship diagrams or a
Complete Data Model

• Entity/Relationship Diagram(ER Diagram) is an abstract
and conceptual representation of data.

• ER modeling is a database modeling method used to
produce a type of conceptual schema or semantic data
model of a system.

• Diagrams created by this process are called Entity
Relationship Diagrams, ER diagrams or ERD’s

Entity and Entity sets
• Entity is an object that exists and is distinguishable from
other objects.

• An Entity may be Concrete (a Person, book, etc) or
Abstract (like bank account)

• An Entity Set is a Set of entities of the same type. (all
persons having an account at a bank)

• Entity sets may not be a disjoint. (example Entity set
Employee (all employees of a bank) and the entity set
customer(all customers of the bank) may have members in
common.

:
Similarity between ERD and programming
language notation
• A Entity represented as a Set of Attributes.
• Name , Street, city, id customer entity
• The domain of the attribute is the set of permitted values(ph
number has minimum 7 to 10 digits)
• Every entity is described by a set of (attribute and value)
pairs.
• Ex:
• Customer: Entity
{(name,priya),(id,1111),(street,North),(city,Chennai)
}

• Entity set corresponds to the programming language
type definition.
• Programming language variable corresponds to an entity
in the ER model.
• Five entity sets:
• Branch  set of all branches of a particular bank.
• Customer set of all people having an account at
the bank
• Employee with attributes(name and ph num
)
• Account  set of all accounts created and
maintained in the bank.
• Transaction  set of all account transactions

Relationships and Relationship Sets

• Relationship is an association between several
entities.
• Relationship set is a set of relationships of the same type.
• A role of an Entity is the function it plays in a
Relationship.
• Relationship “Works for” ordered pairs of
“Employee” .
• Attributes:
Employee  Entity Set
Attributes  Employee name, Employee phone-number
The phone be treated as an entity itself, with attributes phone
number and location.

Mapping Constraints or Cardinality
• ER scheme may define certain constraints.
• Mapping Cardinalities: express the number of entities
to which another entity can be associated via a
relationship. A and B relationship must be:
• One to One: A is associated with at most one entity in
B and B is associated with at must one entity in A.
• One to Many: A is associated with any number in B. An
entity in B is associated with at most one entity in A.
• Many to One: An entity in A is associated with at most
one entity in B. An entity in B is associated with any
number in A.
• Many to Many: Entities in A and B are associated with
any number from each other.

• Existence Dependency: if the existence of entity X
depends on the existence of entity Y then X is said to be
existence Dependent on Y.

Entity Relationship Diagram:
• Graphical Representation:
• Rectangles: entity sets

• Ellipses: attributes

• Diamonds: relationship sets

• Lines: Linking attributes to entity sets to relationship
sets.

One to One Entity Relationship

1:1 1:1
Register
Student
Num

One to Many Entity Relationship

1:M

Football Players
Team
1:M

Many to One Entity Relationship

M:1

customers Bank
M:1

Many to Many Entity Relationship

M:M

Student Subject
M:M

Functional Model
• Structures Representation of the functions or process
within the subject area.

• Also known as activity model or process model.

• Graphical representation.

• Used to describe the functions and processes.

• Identify opportunities.

Data Flow Diagram
• Shows the flow of data through a system.

• Any complex system will not perform the transformation
in a “single Step”.

• It aims to capture the transformations that take place
within the system to the input data so that eventually
the output data is produced.

• Input to output transformations is called “ Process”.

• 2 types:

• Physical  used in “Analysis phase”

• Logical  “Design Phase”.

Elements of Data Flow Diagram:

External Entity
• External Entity:

• Processes: Processes

Data Store
• Data Store :
or

• Data Flow:

Data flow

• External Entity : determine the system boundary.
• May represent the another system.
• Processes: work or actions (no subject)
• Inputs and outputs
• Always “Running” state
• Major functions are Computations
and making decisions.
• Data Store: act as repository.
• Temp or permanent.
• 2 or more systems can share the data.

Rules for drawing DFD:
• Process must have one input and one output flow.

• Never label a process with an IF-Then statement.

• Never show time dependency directly on DFD.

• A process begins to perform its tasks as soon as it received the
necessary input data flows.

• A primitive process performs a single Well-Defined Function.

• Be sure that data Stores, Data Flows, Data Processes have
descriptive titles. Processes should use imperative verbs to project
action.

• All processes receive and generate at least one data flow.

• Begin/End data flows with the Bubble.

Guidelines for drawing DFD:
• Identify the key processing system.
• Process bubbles should be arranged from top left to
bottom right.
• Name each data flow with noun.
• Data stores and destinations are also named with noun.
• Number the each processes.(1.0, 2.0) name the
process with verb.
• Summarize the entire system as one bubble and shows
inputs and outputs to a system.
• Don’t change the inputs and outputs.
• Do not try to put everything know on the DFD.

Functional Modeling Methods

• Functional Flow Block Diagram.

• N2 chart.

• IDEFO

• Axiomatic Design

• Operator Function Model

• Business Process Modeling Notation.

• HIPO and IPO hierarchical input process output.

Data and functional modeling

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