Requirements Modeling

Requirements Modeling

Few questions

What are models?

Why do we model?

What do we model?

(c) Adaptive Processes Consulting Be with the Best!

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Lets understand this paragraph

• ABC Technologies carries out 2 kinds of projects– Milestone based – Billed at end of

a milestone– Time and Material – Billed on

based on effort spent in a period• Milestone based projects are

invoiced at the end of a milestone as per agreement with the client.

• T&M projects are billed on monthly basis based on effort spent in the project or a fixed amount based on agreement with client

• For domestic project, service tax needs to be applied.


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Lets look at this picture


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Which one will the developer get it correct?

Video on Need for Modelling (iRise Video)

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What are models• Models are simplified

representation of reality• They abstract and simplify

reality• Models are represented by text

and by diagrams• Models are likely to be less

mis-understood by practitioners

• Models is wide usage are– Data models such as Entity

Relationship diagrams, Class diagrams

– Activity models such as Activity Diagrams and Process Models

– Decision models such as Flow Charts, Decision Tree, Decision Tables

– Roles(c) Adaptive Processes Consulting Be with the Best!

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What do we model• Concepts

– Relationship between concepts

– Generalization and inheritance

• Events• Actors

– Roles


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Modeling systems• Structured system

analysis and design– Entity relationship

diagram– Data flow diagram

• Use case modeling

(c) Adaptive Processes Consulting 10

Modeling data• Data attributes that the

organization (system) needs to maintain

• Grouping of data attributes (Entities)

• Relationships between the entities• Entities can be

– Physical– Conceptual

• Entity Type Vs. Entity Occurrence


Entity relations• One to One

– May not require additional entity• One to Many

– Office to Employees– Mandatory– Optional

• Many to Many– Books and Publishers


Object modeling• Objects

– Items for which system maintains data

• Class– Object Type– Attributes– Methods– Optional

• Inheritance and generalization


How is object oriented development different from structured approach?

Use Case Modeling

Use case modeling• A use case is a scenario that

describes the use of a system by an actor to accomplish a specific goal.

• An actor is a user playing a role with respect to the system - people, other systems.

• Scenario - A sequence of steps that describe the interactions between an actor and the system.

• The use case model consists of the collection of all actors and all use cases.

• Capture the system's functional requirements from the users' perspective

• Actively involve users in the requirements-gathering process

• Provide the basis for identifying major classes and their relationships

• Serve as the foundation for developing system test cases

Sample use case model• Actor

– User role– Another system– Time

• Use Case• System Boundary• Use case associations

– Include - Included use case embodies common behavior

– Extend - Extending use case adds behavior


http://www.zicomi.com/viewUseCaseDiagram.jsp

Use case diagram


Set up Project

Assign Resources

Track Progress

Print Progress Report

Provide Invoice Data

Print Personal Schedule

Summarize Projects

Identify Projects

Project Manager

Programm Manager

Team Member

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Finance system

Project Control System

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Scenarios Scenario is another

name for a particular flow of events.

A use case covers a range of situations – a scenario is just one.

Each use case typically has:

– a main flow describing the “happy path”

– alternate flows describing major exceptions

Several alternatives exist for specifying the use case scenarios.

Class diagram


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Concepts in Class diagram

• Association– A relationship between instances of the two classes. There

is an association between two classes if an instance of one class must know about the other in order to perform its work. In a diagram, an association is a link connecting two classes.

• Composition / Aggregation– An association in which one class belongs to a collection.

An aggregation has a diamond end pointing to the part containing the whole. In our diagram, Order has a collection of OrderDetails.

• Generalization– an inheritance link indicating one class is a super class of

the other. A generalization has a triangle pointing to the super class. Payment is a super class of Cash, Check, and Credit


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Concepts in Class diagram

• Multiplicity– Multiplicity of an association end is the number of

possible instances of the class associated with a single instance of the other end. Multiplicities are single numbers or ranges of numbers. In our example, there can be only one Customer for each Order, but a Customer can have any number of Orders.

• Navigability– A navigability arrow on an association shows which

direction the association can be traversed or queried. An OrderDetail can be queried about its Item, but not the other way around. The arrow also lets you know who "owns" the association's implementation; in this case, OrderDetail has an Item. Associations with no navigability arrows are bi-directional.


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MultiplicitiesMeaning

0..1zero or one instance. The notation n . . m indicates n to m instances.

0..* or *no limit on the number of instances (including none).

1 exactly one instance1..* at least one instance

Package diagram


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How and when package diagrams are useful?

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Activity diagram• Activity diagrams are an

easy way to represent the high-level flow of activity.

• Show how activities connect to one another in a process.

• Sequential or concurrent activities

• Often used to:– model the flow of events in

a use case– model business processes– model internal system

processes• Not easy to tell who is

responsible for the behavior.

How and when activity diagrams are useful?

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State diagram Use case analysis often

reveals state-based behavior.

Exception flows may occur based on state.

The user may operate directly on the state of something in the system.

How and when state diagrams are useful?

Open

Implemented

Assigned

Fixed

Cancel

Prototyping


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Demo of Process Modeling Tool – BizAgi Process Modeler


Demo of UML Tool – STAR UML


Lets develop a sample process model and Use case

diagram for training process.

Time : 30 Minutes


Documents

Requirements Modeling