Data and functional modeling

transcript

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

One to One Entity Relationship

Student Register

1:1 1:1

One to Many Entity Relationship

Football Team

Players

Many to One Entity Relationship

customers Bank

Many to Many Entity Relationship

Student Subject

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:

• Processes:

• Data Store :

External Entity

Processes

Data Store

• 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.

Data flow

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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