Previous Lectures Information flows Specification and Documentation Techniques: Graphical Notations (2) CS/SE 3RA3 Ryszard Janicki Department of Computing and Software, McMaster University, Hamilton, Ontario, Canada Ryszard Janicki Graphical Notations (2) 1/20
20
Embed
Speci cation and Documentation Techniques: Graphical ...
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Previous LecturesInformation flows
Specification and Documentation Techniques:Graphical Notations (2)
CS/SE 3RA3
Ryszard Janicki
Department of Computing and Software, McMaster University, Hamilton,Ontario, Canada
Components / terminators / external entities / adjacentsystems → boxes or other shapes
Data stores / depository → horizontal lines or other shapes
Data / material / information flows → arrows
Dataflows have hierarchical structure → each black box (i.e.circle/bubble) can be expanded
Ryszard Janicki Graphical Notations (2) 9/20
Dataflow diagrams: chemical tracking system
Previous LecturesInformation flows
Context diagramsDataflow diagramsContext diagrams vs Dataflow diagramsDataflows vs Entity-relationship diagrams
Dataflow diagrams: meeting schedule
Dataflow diagram: example
copyOf
input data flow output data
flowInitiator
copyOfconstraintsRequestmeeting
Request
Participant
ti
invalidRequest
flow
AskConstraints
t i tR tmeeting
C t i tC ll t M Determine
meetingNotificationCheck
Request
RequestvalidRequest operation
constraintRequest Constraints
individualC t i t
CollectConstraints
Participant
MergeConstraints
DetermineSchedule
Constraints participantConstraints
data repositorysystem component
Ryszard Janicki Graphical Notations (2) 11/20
Dataflow diagrams: university
Dataflow diagrams: bank
Dataflow diagrams: filling orders
Example (Elevator: Data Flow)
Data-Flow Diagram
14
Previous LecturesInformation flows
Context diagramsDataflow diagramsContext diagrams vs Dataflow diagramsDataflows vs Entity-relationship diagrams
Some rules (may not always be followed)Always start with context diagramProcesses communicate through system components and datastores, not by direct flows from one process to another (thisrule is not always followed, see ‘Meeting Schedule’).Similarly, data cannot flow directly from on store/componentto another; it must pass through a process bubble (this rule isalways followed).Do not attempt to imply the processing sequence usingthe dataflow diagrams.Name each process as a concise action: verb + object(generate inventory reports).Number the processes uniquely and hierarchically, for instancenext level for 3 should be 3.1, 3.2 and so on.No more that 8-10 processes on a single diagram.Avoid bubbles with only inputs and only outputs.
Ryszard Janicki Graphical Notations (2) 16/20
Contex diagrams as simplified dataflow diagrams: one“bubble”
Previous LecturesInformation flows
Context diagramsDataflow diagramsContext diagrams vs Dataflow diagramsDataflows vs Entity-relationship diagrams
From context diagrams to dataflow diagrams: ChemicalTracking System
Ryszard Janicki Graphical Notations (2) 18/20
Previous LecturesInformation flows
Context diagramsDataflow diagramsContext diagrams vs Dataflow diagramsDataflows vs Entity-relationship diagrams
From context diagrams to dataflow diagrams: FillingOrders
Ryszard Janicki Graphical Notations (2) 19/20
Previous LecturesInformation flows
Context diagramsDataflow diagramsContext diagrams vs Dataflow diagramsDataflows vs Entity-relationship diagrams
Relationship between Dataflows and ER diagramsEntities often correspond to data depositories of dataflows