Dataflow Diagrams

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Dataflow Diagrams
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Modeling notations

• A graphical modeling notation focuses on one
  aspect of a system
• Several models are needed to give a complete
  picture
• Models must work together
• No set of modeling notations is perfect

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UML Models

• Use case diagrams and use cases
• Class diagrams
• Sequence diagram (event trace)
• Object diagram
• Package diagram
• Deployment diagrams
• State machine diagram
• Activity diagram
• Communication diagram
• Component diagrams
• Interaction overview diagrams
• Timing diagrams

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Structured Analysis Models

• Process
• Data-flow diagram
• Process specification
• Data
• Entity-Relationship Diagrams
• Data dictionary
• Control
• Control flow diagram
• State-transition diagram

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Elements of Dataflow Diagram

• Boxes (bubbles)
• Process - information transform
• External entity source/sink
• Data store
• Line
• Data item - Flow of information

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Health Claims Processing

• R1) Receives health claims and supporting
  documents via many sources electronically, fax,
  on paper.
• R2) Scanned paper and fax processed by OCR.
  Documents first subject to form dropout,
  deskewing, despeckling.
• R3) All images are logged to optical disk.

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• R4) Fields with low confidence levels are
  repaired by hand. Certain types of claims are
  transmitted to an offshore data entry vendor.
• R5) Match the plan and the health care provider.
• R6) Existing mainframe system processes accepted
  claims.

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• R7) Determine if claim can be paid, and how
  much. If there are inconsistencies, suspend the
  claim until a human (adjudicator) can look at it.
• R8) Adjudicator looks at documents about claim
  and history of client and can ask for more
  information, can accept claim, or can reject
  claim.

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Dataflow Diagram
Adjudicator
Web site
claims
Mainframe
Accept claim
Claim Processing System
claim images
Fax
Request more info. Rejection
claim images
Paper claims
Postal system
database
claims
Manual
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Claim Processing System
Adjudicator
Mainframe
accept claim
Web site
claims
claims
Automatic claims processing
Rejection notice
claims
Postal system
rejection
Make claims
2
claims
request more info.
Adjudication
1
claim images
claim images
claims
3
database
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Process decomposition

• What happens inside a process?
• Another dataflow diagram!
• Prefix process numbers with number of parent
  process

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Process 1 Make claims
claims
claims
claims
Manual repair
OCR
1.2
1.1
claim images
claim images
database
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Process specification

• What happens inside a bubble?
• Used for lowest level of detail.
• Describe how inputs are converted to outputs.
• Use
• English
• Pseudo-code
• Formulas or program

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Process 1.1 OCR

• Apply
• form dropout algorithm
• deskewing algorithm
• despeckling algorithm
• OCR algorithm
• If any character is less than 99.9 reliable,
  send to manual repair, else submit for claim
  processing.

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Control

• What is the order of events?
• How fast must the system respond to an event?
• What are the possible states of the system?

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Control models

• Control Flow Diagram (DFD)
• State machine (State Transition Diagram)

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Control Flow Diagram
adjudicator
accept claim
Adjudicator ready
Automatic claims processing
claims
Claim ready
rejection
OCR
request more info.
Adjudication
claim images
database
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State transition diagram
Adj. ready
Work queue empty Worker busy
Adj. ready
claim ready
claim ready
Work queue empty Worker waiting
Work queue nonempty Worker busy
claim ready
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UML vs. DFD

• UML designed for OO systems
• Concentrates on structure
• Control flow and data flow secondary
• DFD designed for procedural systems
• Process corresponds to a procedure
• Data structure secondary

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Conclusion

• Need a SET of models
• Building one model shows flaws in others
• Reviews must check for consistency
• No set is perfect - you may need to add a model

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Software Quality Assurance

• How can you tell if software has high quality?
• How can we measure the quality of software?
• How can we make sure software has high quality?

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Perspective on quality

• Customer
• system not crashes
• system follows documentation
• system is logical and easy to use
• Developer
• system is easy to change
• system is easy to understand
• system is pleasant to work on

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Mistakes about SQA

• Quality is conformance to requirements and
  standards.
• Variation control is the heart of quality
  control.
• Feedback and continual improvement is the real
  heart of quality software.

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Total Quality Management

• Factories
• Goal is for every item coming off the assembly
  line to be perfect
• Management, production, engineering, QA
• Everyone is involved in quality
• Develop a reliable, repeatable process
• Continuously improve the process

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Quality is free
Effort
Quality
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Failure vs. flaw

• Failure - program didnt work right
• Flaw - mistake in the text of the program
• Failure analysis - what flaw caused this failure?
• Flaw analysis - what is wrong with our process
  that allowed this flaw to be created and not
  detected?

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Failure costs

• Internal
• rework
• repair
• failure analysis
• External
• resolving complaints
• returning and replacing product
• help line

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Prevention costs

• Prevention
• planning
• managing and collecting information
• reviews
• Appraisal
• inspection
• testing

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Next time

• More on quality assurance
• Inspections and Reviews