Business Analysis Session3

7/31/2019 Business Analysis Session3

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BUSINESS ANALYSIS

DAY-3

Vamsi Mohan V


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AGENDA

(DAY-3) Modeling

State Machine Diagrams

Sequence Diagrams

Data flow diagrams


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Modeling


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State Machine Diagrams A state machine diagram models the behavior of a single object, specifying the

sequence of events an object goes through during its lifetime in response to events.

As an example, the following state machine diagram shows the states that a door

goes through during its lifetime.

The door can be in one of three states: Opened, Closed or Locked. It canrespond to the events Open, Close, Lock and Unlock. Not all events are valid in allstates; for example, if a door is opened, you cannot lock it until you close it. Alsonotice that a state transition can have a guard condition attached: if the door is

opened, it can only respond to the Close event if the condition doorWay->isEmpty isfulfilled.


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StatesA State is denoted by a round-cornered rectangle with the name

of the state written inside it.

Initial and Final States

The initial state is denoted by a filled black circle and may be abeledwith a name. The final state is denoted by a circle with a dot inside,and may also be labelled with a name.


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Transitions Transitions from one state to the next are denoted by lines with

arrowheads. A transition may have a trigger, a guard and an effect,as below.

Trigger is the cause of the transition, which could be a signal, anevent, a change in some condition, or the passage of time. Guardis a condition which must be true in order for the trigger to cause thetransition. Effect is an action which will be invoked directly on theobject that owns the state machine as a result of the transition.


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State Actions In the transition example above, an effect was associated with the

transition. If the target state had many transitions arriving at it, andeach transition had the same effect associated with it, it would be

better to associate the effect with the target state rather than thetransitions. This can be done by defining an entry action for the state.The diagram below shows a state with an entry action and an exitaction.

It is also possible to define actions that occur on events, or actionsthat always occur. It is possible to define any number of actions ofeach type.


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Contd.,

Self-Transitions

A state can have a transition thatreturns to itself, as in the following

diagram. This is most useful when aneffect is associated with the transition.

n ry o n

The following sub-machine itwould be normal to begin in theInitializing state, but if for somereason it wasnt necessary to

perform the initialization, it wouldbe possible to begin in theReady state by transitioning tothe named Entry Point.


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Exit Point

In a similar manner to entry points, it is possible to have namedalternative exit points. The following diagram gives an example

where the state executed after the main processing state depends onwhich route is used to transition out of the state.


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Modeling


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Sequence Diagrams A sequence diagram is a form of interaction diagram that shows objects as

lifelines running down the page, with their interactions over time representedas messages drawn as arrows from the source lifeline to the target lifeline.

Sequence diagrams are good for showing which objects communicate withwhich other objects, and what messages trigger those communications.Sequence diagrams are not intended for showing complex procedural logic.

Lifelines

e ne represen s an n v ua par c pan n a sequence agram.lifeline will usually have a rectangle containing its object name. If its name isself, that indicates the lifeline represents the classifier which owns thesequence diagram


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Contd., Sometimes a sequence diagram will have a lifeline with an actor

element symbol at its head. This will usually be the case if thesequence diagram is owned by a use case. Boundary, control and

entity elements from robustness diagrams can also own lifelines.


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Messages Messages are displayed as arrows. Messages can be complete, lost

or found; synchronous or asynchronous; call or signal. In thefollowing diagram, the first message is a synchronous message

(denoted by the solid arrowhead) complete with an implicit returnmessage; the second message is asynchronous (denoted by linearrowhead), and the third is the asynchronous return message(denoted by the dashed line).


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Execution Occurrence

A thin rectangle running down the lifeline denotes the executionoccurrence, or activation of a focus of control. In the previousdiagram, there are three execution occurrences. The first is thesource object sending two messages and receiving two replies; thesecond is the target object receiving a synchronous message and

asynchronous message and returning a reply.


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Self Message Self Message

A self message can represent a recursive call of an operation, or onemethod calling another method belonging to the same object. It is

shown as creating a nested focus of control in the lifelines executionoccurrence.


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Modeling


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Data flow diagrams Data flow diagrams (DFDs) reveal relationships among and between

the various components in a program or system. DFDs are animportant technique for modeling a systems high-level detail by

showing how input data is transformed to output results through asequence of functional transformations. DFDs consist of four majorcomponents: entities, processes, data stores, and data flows.

Symbols of Data Flow Diagram

There only four symbols used to write Data Flow Diagram as follows:

External Entities > Rectangular box

Data Flow > Arrow headed lines

Process > Bubble (Circle or round corner square)

Data Store > Narrow opened rectangle


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Symbols of Data Flow Diagram


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Modeling


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Data Dictionary A tool for recording and processing information

(metadata) about the data that an organisation uses.

A central catalogue for metadata. Can be integrated within the DBMS or be separate.

Ma be referenced durin s stem desi n

programming, and by actively-executing programs. Can be used as a repository for common code (e.g.

library routines).


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Benefits of a DDS Benefits of a Data Dictionary are mainly due to the fact

that it is a central store of information about thedatabase.

Benefits include -

improved documentation and control

easier data analysis

reduced data redundancy

simpler programming

the enforcement of standards

better means of estimating the effect of change.


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Session Review:

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Business Analysis Session3

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