Object Oriented Analyis

1
C H A P T E R
9
PROCESS MODELING - part 2
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Data Structures

• Data flows can be defined by data structures.
• A data structure is a specific arrangement of
  data attributes that defines the organization of
  data contained in a data flow.
• A data attribute is the smallest piece of data
  that has meaning to the end-users of a business.
• A data structure is not an entity it defines
  the inputs / outputs for each processData
  conservation providing only the data needed for
  the process to complete its task

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Types of Data Structures

• Sequence -
• order-number
• order-date
• Selection one and only one
• personal customer number,
• corporate account number
• Repetition
• 1product-number
• product-description
  n
• Optional ( )
• (post office box number)

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A Data Structure for a Data Flow

• DATA STRUCTURE
• ORDER
• ORDER NUMBER
• ORDER DATE
• PERSONAL CUSTOMER NUMBER,
• CORPORATE ACCOUNT NUMBER
• SHIPPING ADDRESSADDRESS
• (BILLING ADDRESSADDRESS)
• 1 PRODUCT NUMBER
• PRODUCT DESCRIPTION
• QUANTITY ORDERED
• PRODUCT PRICE
• PRODUCT PRICE SOURCE
• EXTENDED PRICE N
• SUM OF EXTENDED PRICES
• PREPAID AMOUNT
• (CREDIT CARD NUMBEREXPIRATION DATE)
• (QUOTE NUMBER)

ENGLISH ENTERPRETATION An instance of ORDER
consists of ORDER NUMBER and ORDER DATE
and Either PERSONAL CUSTOMER NUMBER or
CORPORATE ACCOUNT NUMBER and SHIPPING ADDRESS
(which is equivalent to ADDRESS) and
optionally BILLING ADDRESS (which is equivalent
to ADDRESS) and one or more instances
of PRODUCT NUMBER and PRODUCT DESCRIPTION
and QUANTITY ORDERED and PRODUCT PRICE
and PRODUCT PRICE SOURCE and EXTENDED
PRICE and SUM OF EXTENDED PRICES and PREPAID
AMOUNT and optionally both CREDIT CARD NUMBER
and EXPIRATION DATE An instance of ADDRESS
consists of optionally POST OFFICE BOX NUMBER
and STREET ADDRESS and CITY and Either STATE
or MUNICIPALITY and optionally COUNTRY and
POSTAL CODE
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Data Structure Constructs
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Data Structure Constructs (concluded)
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Data Types and Domains

• Data attributes should be defined by
• data types
• Domains
• Data type defines the class of data
• character
• integers
• real numbers
• dates, etc.
• Domain defines values or range of values an
  attribute can legitimately take on.

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Diverging and Converging Data Flows

• A diverging data flow is one that splits into
  multiple data flows.
• Useful for illustrating data that starts out
  naturally as one flow, but needs to be routed to
  parallel processes.
• Also useful for illustrating multiple copies of
  the same output going to different destinations.
• A converging data flow is the merging of multiple
  data flows into a single packet.
• Useful for illustrating data from multiple
  sources that must come back together for some
  subsequent processing

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Diverging and Converging Data Flows
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External Agents

• An external agent defines a person, organization
  unit, or other organization that lies outside of
  the scope of the project but that interacts with
  the system being studied.
• Provides net inputs / Receives net outpus
• External agents define the boundary or scope of
  a system being modeled.
• As scope changes, external agents can become
  processes, and vice versa.
• Almost always one of the following
• Office, department, division inside the business
  but outside the system scope.
• An external organization or agency.
• Another business or another information system.
• One of your systems end-users or managers
• Named with singular nouns

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Data Stores

• A data store is an inventory of data.
• Frequently implemented as a file or database.
• A data store is data at rest compared to a data
  flow that is data in motion.
• Almost always one of the following
• Persons (or groups of persons)
• Places
• Objects
• Events (about which data is captured)
• Concepts (about which data is important)
• Data stores depicted on a DFD store all instances
  of data entities (depicted on an ERD)
• Named as plural of the entity
• It stores all the instances of the entity

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When to Draw Process Models

• Strategic systems planning
• Enterprise process models illustrate important
  business functions.
• Business process redesign
• As is process models facilitate critical
  analysis.
• To be process models facilitate improvement.
• Systems analysis (primary focus of this course)
• Model the existing system including its
  limitations
• Model the target systems logical requirements
  (meaning processes and data flows needed
  regardless of how the system will be implemented)
• Model candidate technical solutions (physical
  DFDs only)
• Model the target technical solution (physical
  DFDs only)

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Modern Structured Analysis

• Draw a context DFD to establish initial project
  scope.
• Draw a functional decomposition diagram to
  partition the system into subsystems.
• Create an event-response or use-case list for the
  system to define events for which the system must
  have a response.
• Draw an event DFD (or event handler) for each
  event.
• Merge event DFDs into a system diagram (or, for
  larger systems, subsystem diagrams).
• Draw detailed, primitive DFDs for the more
  complex event handlers.
• Document data flows and processes in the data
  dictionary.
• THE ABOVE METHODOLOGY, BASED ON EVENT
  PARTITIONING, IS MORE COMMONLY PRACTICED.

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Structured Analysis Diagram Progression An
event drive process (1 of 3)
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Structured Analysis Diagram Progression (2 of 3)
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Structured Analysis Diagram Progression (3 of 3)
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CASE for DFDs (Sample Screen) from System
Architect 2001
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SoundStage Functional Decomposition Diagram
XOR_Cntr_1
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Events

• Events define processes needed to respond to
  those events.
• External events are those initiated by external
  agents. They result in an input transaction or
  data flow.
• Temporal events are those that are triggered by
  the passage of time. They simply happen and
  are indicated by a control flow.
• State events are those based on a systems change
  from one state to another.

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Use Cases

• Use cases are based upon object-oriented concepts
  that are essentially the same as events.
• Use case analysis is the process of identifying
  and modeling business events and how the system
  responds to them.
• An actor is anything that needs to interact with
  the system (essentially, a synonym for external
  agent).
• Actor becomes external agents
• Event to be handled by process
• Input / Trigger becomes data flow

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Use Case List
Actor
Event (or Use Case)
Trigger
Responses




NEW MEMBER SUBSCRIPT
ION
Marketing

Establishes a new
Generate
SUBSCRIPTION

PROGRAM
membership subscription plan
.

PLAN CONFIRMATION
to entice new members.

Create
in the
AGREEMENT
database.

Marketing

Establishes
a new
Generate
PAST MEMBER
SUBSCRIPTION
membership resubscription
.

RESUBSCRIPTION PROGR
AM
PLAN CONFIRMATION
plan to lure back former
Create
in the
AGREEMENT
members.

database.

Marketing

Changes a subscription plan
Generate
SUBSCRIPTION PLAN
AGREEMENT
for current members (e.g.,
.

.

CHANGE
CHANGE CONFIRMATION
extending the
fulfillment
Update
in the
AGREEMENT
period)

database.

(time)

A subscription plan expires.
(current date)

Generate
AGREEMENT
.

CHANGE CONFIRMATION
Logically Delete (void)
in the da
tabase.
AGREEMENT
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Use Case List (continued)
Actor
Event (or Use Case)
Trigger
Responses
Generate
Marketing

Cancels a subscription plan
.

before its planned expiration

CHANGE CONFIRMATION
CANCELATION

Logically Delete (void)
in the database.

AGREEMENT
Generate
Member

Joins the club by subscribing.

MEMBER
NEW SUBSCRIPTION
(Take any 12
CDs for one
DIRECTORY UPDATE
.

penny and agree to buy 4
CONFIRMATION
more at regular prices within
Create
in the
MEMBER
two years.)

database.

Create first
MEMBER ORDER
MEMBER ORDERED
s in the database.

PRODUCT
Generate
Member

changes address


MEMBER
CHANGE OF ADDRESS
DIRECTORY UPDATE
(including email and privacy
.

CONFIRMATION
code)

Update
in the
MEMBER
database.

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Use Case List (continued)
Actor
Event (or Use Case)
Trigger
Responses
Generate
Changes members credit
Accounts

CREDIT
CHANGE OF CREDIT STA
TUS
status

Receivable

DIRECTORY UPDATE
.

C
ONFIRMATION
Update
in the
MEMBER
database.

Generate
90 days after a Marketing
(time)

(current date)

CATALOG CHANGE
.

decides to no longer sell a
CONFIRMATION
product.

Logically Delete
(deactivate)
in the
PRODUCT
database
.

Generate
Wants to pick products fo
r
Member


CATALOG
PRODUCT INQUIRY
.

possible purcase.

DESCRIPTION
(Logical requirement is driven
by vision of web
-
based access
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Event Decomposition Diagram (partial)
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External Event DFD
Updated
Club
Member
Member Change
Process
Member
Address
of Address
Member
Members
Address
Change
Member Updated Address Confirmation
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External Event DFD (more complex)
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Temporal Event DFD
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System DFD (see book for more readable copy)
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Primitive DFD (see book for more readable copy)
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Data Structure for a Primitive Data Flow
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Logic for a Primitive Process
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Data to Process CRUD Matrix
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Process to Location Association Matrix
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Questions?