The OOD Process - IV

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The OOD Process - IV

• The Task Management Component
• (TMC)
• Coad/Yourdon

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The OO Co-Design ProcessThe Task Management
Component
extend
TMC
HIC
PDC
DMC
high-level Design
Miniworld
refine map
detailed Design
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TMC - What is it?

• Task A stream of activity.
• Support in your OOD
• multitasking
• concurrency
• priorities
• transactions
• set of activities as atomic action
• role-back, commit, etc.
• map your needs to the infrastructure
• tool-specific solutions
• guided by a common architecture

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TMC tasks

• check the type of task(s) you need
• event-driven tasks
• clock-driven tasks
• etc.
• check priorities
• identify a coordinator
• define each task object

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TMC tasks - types event-driven I

• life-cycle
• task sleeps
• triggered upon event arrival of data
• data line
• data buffer
• read format data
• place in an internal buffer (send messages
  directly)
• notify objects.services
• check on proper sequence
• handle errors

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TMC tasks - types event-driven II

• might be programmed as a distributed solution
• scenario as in OOA
• error handling
• low dependency of involved activities (services)
• if any of the above conditions does not hold
• centralized task object
• in IS world transaction handler
• also called controller

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TMC tasks - types clock-driven I

• life-cycle
• task sets a wake-time and sleeps
• triggered by time
• read format data (if necessary)
• notify objects.services
• check on proper sequence (if necessary)
• handle errors
• set a new wake-time
• go to sleep

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TMC tasks - types clock-driven II

• might be programmed as a distributed solution
  or
• centralized task object
• less usual than for event-driven
• complements event-driven tasks
• in principal equivalent

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TMC tasks - check priorities

• priorities help to manage resources
• not easy to design and implement
• use existing task managers and priority schemata
• indicates need for a coordinator
• identify and isolate critical tasks
• stringent reliability constraints
• critical to the success or failure of the system

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TMC tasks - identify a coordinator

• task of tasks manager
• three or more tasks
• priorities and interrupts
• complex transactions
• adds overhead
• encapsulates task-management
• only trigger services, do not implement them in
  the coordinator

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TMC tasks - define task objects

• name
• description
• priority
• services included
• sequence of call
• error handling
• coordinates by
• trigger or time (interval)
• communicates via
• data comes where from, goes where to

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Task Coordinator
A Task-Object Pattern
coordinate
1,m
1,1
task
name description priority services_included coordi
nates_by communicates_via
initialize start terminate
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Keep tasks to a minimum.

• Use existing solutions.

• Think in Architectures!