MIT5312: Professor Kirs Modeling Tools Slide 1
Modeling Tools
MIT5312: Professor Kirs Modeling Tools Slide 2
TOPICSTOPICS Systems Concepts
• Why??? Modeling Diagram Conventions
• The Rules of the Game Modeling Diagrams
• Basic Principles• Context Diagrams• Decomposition Diagrams• Data Flow Diagrams
MIT5312: Professor Kirs Modeling Tools Slide 3
Information Environment
Systems Concepts• Systems Thinking
• Application of formal Systems theory and concepts
Information System
INPUTS
Business Environment
Operating EnvironmentBusiness Strategy
Government Mandates
Organization Policies
OUTPUTS
• The Information Environment• Constantly changing along
with Social, Business and Organizational changes
• The Information System• The Collection of inter-
related systems/packages
• System Inputs• Data from the Organization,
external sources, other systems, or self-generated
• System Outputs• Reports, Screens, Files, Data
to other systems, etc.
Feedback and Control Loop
• Feedback & Control Loop• Self-Monitoring &Modification
(Thermostatic Control)
MIT5312: Professor Kirs Modeling Tools Slide 4
Systems Concepts• Systems Thinking• Process Concepts
• Historically, IS were focused on individual business functions
Sales Production
Marketing
Service
Finance Accounting
• IS were developed for each functional Area
Marketing IS Finance IS Accounting IS
Sales IS Service IS Production IS
INPUTS
OUTPUTS
INPUTS
OUTPUTS
INPUTS
OUTPUTS
INPUTS
OUTPUTS
INPUTS
OUTPUTS
INPUTS
OUTPUTS
• Each IS was intended to process or transform the inputs to outputs
MIT5312: Professor Kirs Modeling Tools Slide 5
Systems Concepts• Systems Thinking• Process Concepts
• It later became obvious that some functions were inter-related, and Cross-functional IS were needed
INPUTS
INPUTS
Marketing
Marketing IS
Accounting
Accounting IS
Sales
Sales IS
Finance
Finance IS
INPUTS
INPUTS
Cross-Functional IS
to get input from each functional area,Process it, and return it to the individual functional systems as input
MIT5312: Professor Kirs Modeling Tools Slide 6
Systems Concepts• Systems Thinking• Process Concepts
• The emphasis today is to have an Enterprise Model which will encompass the entire organization (individual functional Area IS Still in Existence)
INPUTS
Marketing
Marketing IS
Accounting
Accounting IS
Sales
Sales IS
Finance
Finance IS
Service
Service IS
Production
Production IS
Information System
OUTPUTS
MIT5312: Professor Kirs Modeling Tools Slide 7
Systems Concepts• Systems Thinking• Process Concepts
• The emphasis Corresponds to the idea of a system as a business• A business operates within a constantly changing system• A business has various actors who impact it (Customers, Suppliers,
Competitors, Government)• A business has various inputs (Raw Materials, Services, Equipment)
• A business Transforms goods (WIP, Value-Added Services)
• A business has various Outputs (Products, Services)
• A business operates in a synergistic manner
• The Change in System Processing reflects the trend in Business Process Redesign (BPR)• The emphasis is in not merely improving on the existing system, but in re-
inventing the manner in inputs are processed
MIT5312: Professor Kirs Modeling Tools Slide 8
Modeling Diagram Conventions• Structured Methodology Goals
• Used for requirements specification, systems analysis and systems design
• Intended to structure a project into small, well-defined activities • Specifies the sequence and interaction of these activities • Use diagrammatic and other modeling techniques • Give a precise (structured) definition • Are understandable by both users (clients) and developers
• Structured Methodology (Intended) Advantages• Reduce life cycle development costs through improved analysis and design • Improve quality of systems delivered • Improve project management, planning and control • More effective use of inexperienced staff • Improve communication
• Self documenting
• User Analyst• Designer Analyst• Designer User
MIT5312: Professor Kirs Modeling Tools Slide 9
Modeling Diagram Conventions• Available Methodologies
• Gane & Sarson (Chris Gane and Trish Sarson): Late 1970s• Yourdan: Late 1970s• Demarco: Late 1970s• Merise (France): late 1970s
• Information Engineering (Finkelstein and Martin): Late 1970s/early 1980s • Structured Systems Analysis and Design Method (SSADM): - 1980
??? Which one will we Use ???• Gane & Sarson
??? Why ???
• It is (perhaps) still the most common
??? Are there Differences ???
• Some, but basically trivial:
Process Representation:Process Name
Gane & Sarson
Process Name
Demarco/Yourdan SSADM
Process Name
MIT5312: Professor Kirs Modeling Tools Slide 10
Modeling Diagram Conventions
Rectangle
• Basic Symbols
Source OR Destination of Information
Customer C.E.OSupplier
• Sometimes, for the sake of clarity, an Information source/destination is duplicated
?Customer
SupplierCustomer
• In that case, a duplication symbol is associated with the source/destination
?Customer
SupplierCustomer
• If the source/destination appears more than once, a multiple duplication symbol is used
?Customer
Supplier Customer
Customer
A
BB
B
• Note also that Identifying notation may also be used
MIT5312: Professor Kirs Modeling Tools Slide 11
Modeling Diagram Conventions• Basic Symbols
A Process/Activity which transforms/adds to data
• Processes are generally not duplicated, but can contain identifying notation
Rounded Rectangle Marketing IS Update
InventoryVerify that an Order is valid
Compute Monthly
Sales
35
IDS
Compute Monthly
Sales
4.2
C:/CMS.exe
Process Number Hierarchy/Activity Number
Department Program Name
Function/ Process/ Activity
Description
Identification
Physical Location
MIT5312: Professor Kirs Modeling Tools Slide 12
Modeling Diagram Conventions• Basic Symbols
A data store
• Data stores are generally annotated with a number and descriptive name
Open-ended Rectangle Database File Temp. Storage
Accounts ReceivableD1
CustomerD2
EmployeeD3
InventoryD4
• As with processes, if data stores are duplicated in a diagram, extra lines are added
?Supplier
CustomerD2
CustomerD2
CustomerD2
• Here, the store has 3 lines at the left to indicate it appears 3 times in the diagram
MIT5312: Professor Kirs Modeling Tools Slide 13
Modeling Diagram Conventions• Basic Symbols
A data flow: Information of any sort (written or oral), Invoices, Receipts, Database data, etc.
• The direction of the arrow shows the direction of the flow
• Data flows are ALWAYS assigned names:
?
• Unless it is completely obvious:
Customer CustomerD2
The process receives a payment from a Customer
After Processing, the Customer Database is updated
?Customer CustomerD2Customer Payment Updated Cust. Data
• Data flow names should be unique (unless the same data flow is generated at multiple locations)
Produce Paycheck
Employee(Paycheck)
MIT5312: Professor Kirs Modeling Tools Slide 14
Modeling Diagram Conventions• Basic Symbols
A data flow: Information of any sort (written or oral), Invoices, Receipts, Database data, etc.
• If data flows in both directions, separate arrows should be used (Don’t use )
• Sometimes, data flows can become unwieldy:
?
• In which case we might want to merge data flows
CustomerD2
?
Customer Data ? CustomerD2
Customer Data
Updated Customer
Data
Customer
Customer Order
Customer Payment
Customer Return
Customer Complaint
CustomerCustomer
Transactions?
MIT5312: Professor Kirs Modeling Tools Slide 15
• Analysis/design is still (essentially) a top-down approach
Modeling Diagrams• General Principles
• When we need to, we can ‘explode’ processes
Marketing IS
• Analogous to our previous ‘Forest vs. Tree’ Idea
Marketing IS
~~~
~~~
~~~~
~~~~~~~
~~~~~~~
~~~~
~~~
~~~
• We can continue until there is nothing left to ‘Explode’
MIT5312: Professor Kirs Modeling Tools Slide 16
Modeling Diagrams• Context Diagrams
• Identifies the system boundaries and responsibilities.• Determines the boundaries, actors and interactions required.• Identifies Primary Data Flows
Harpo’s Book Club Members
Potential Subscribers
Suppliers
Customer Order
Invoice
Shipped Product List
Payments
Club Promotion
Subscription Order
Title Announcements
Purchase Orders
Product Invoices
Payments
Publishers
PaymentsInvoicesAdvertising
Agreements
MIT5312: Professor Kirs Modeling Tools Slide 17
• Intended to show all sub-processes and tasks and which can be ‘exploded’
Information System
Marketing Systems
Production Systems
Accounting Systems
Finance Systems
Process Control System
Inventory System
Inventory Receipt System
Inventory Ordering System
Modeling Diagrams• Decomposition Diagrams
Decomposition Diagrams(Hierarchy Chart)
MIT5312: Professor Kirs Modeling Tools Slide 18
Modeling Diagrams• Data Flow Diagrams (DFDs)
• Exploded Context Diagrams• Shows all Processes, sources/destinations of data, data stores, and data flows• Intended to be top-down
CustomerCustomer
Order
Verify Order
Pending OrderD3
Valid
Order
Process
Order
CustomerD1
Credit Status
BooksD2
Book Details
Gather Publisher
Requisition
PublisherD2
Publisher Address
Publisher
Purchase Order
MIT5312: Professor Kirs Modeling Tools Slide 19
Modeling Diagrams• Data Flow Diagrams (DFDs)
• Basic DFD Guidelines
1. Identify External Entities involved
2. For Each Entity, Identify scheduled inputs and Outputs
• Data Flows are Not Physical ProductsNote:
3. For each Entity Input and Output, determine which process the receives the entity outputs and which process will generate the entity inputs
• Book Invoices are shipped, not the Books themselves
?
4. For Each Process, Identify what data stores need to be accessed for inputs and which data stores will be updated or given new outputs
?
MIT5312: Professor Kirs Modeling Tools Slide 20
Modeling Diagrams• Data Flow Diagrams (DFDs)
• Basic DFD Guidelines
• Data Flows MUST ALWAYS flow to or from a ProcessNote:
? ??
MIT5312: Professor Kirs Modeling Tools Slide 21
Modeling Diagrams• Data Flow Diagrams (DFDs)
• Basic DFD Guidelines
• Processes MUST ALWAYS have inputs AND OutputsNote:
? ?
Generate Employee Banking
Statement
A Black Hole A Miracle
• The inputs to a process must be sufficient to produce the output
Where did the Accounting Information Come From ??
Employee Data
EmployeeEmployee
Address
Bank
Statement
A Grey Hole
MIT5312: Professor Kirs Modeling Tools Slide 22
Modeling Diagrams• Data Flow Diagrams (DFDs)
Verify Order
1.1
Assemble Publisher
Requisition
1.2
Verify Shipment
1.3
Assemble Customer
Order
1.5
Assign Shipment
1.4
Process Order
1.0
• Exploding DFDs
• Processes should be exploded according to the Decomposition Chart
1.0: Process Order
• Notice that at this point in time, all we are doing is listing the activities Involved
• We should, however, be able to determine (approximately) the order of processing, and assign identifiers accordingling
MIT5312: Professor Kirs Modeling Tools Slide 23
Modeling Diagrams• Data Flow Diagrams (DFDs)
• Exploding DFDs
• Of Course, we will have to add details
Customer
Verify Order
1.1
Pending OrderD3
Valid
Order
Process Order
Publisher
PublisherD4Publisher
Address
Publisher OrdersD5
PO Details
Purchase Order
Publishers Consign.
NoteTitle
Quant.
Order
Details
Customer Order
Customer
Data
Ship.
Note
Title Orders
Order Details
Assemble Publisher
Requisition
1.2
Verify Shipment
1.3
Assemble Customer
Order
1.5
Assign Shipment
1.4
1.0: Process Order
BooksD2 Book Details
CustomerD1
Credit Status
MIT5312: Professor Kirs Modeling Tools Slide 24
Modeling Diagrams• Data Flow Diagrams (DFDs)
• Exploding DFDs
• We can now continue Exploding
Publisher
Copy of PO
Order Date, PO#
Assemble Publisher
Requisition
1.2.4.
Copies Total Number of
Copies
1.2.3.
Note Order Info. In Pending Orders
1.2.6. 1.2.5
Create PO in Progress Record
1.2: Assemble Publisher Requisition
PublisherD4
Pending OrderD3
Publisher Ordering Information
Pending Order Details
Retrieve Pub. Order
Info.
1.2.1.
Extract Publisher
Orders
1.2.2
Totals by
Title
Unit
Orders
Publisher Address
Business Terms
P.O
Publisher OrdersD3P.O
Details
Order Details
MIT5312: Professor Kirs Modeling Tools Slide 25
Modeling Diagrams• Data Flow Diagrams (DFDs)
• Exploding DFDs
??? When Do We Stop ???
When We are done
MIT5312: Professor Kirs Modeling Tools Slide 26