Software modeling for embedded systems: static and dynamic behavior
Important concepts in embedded systems:
--concurrency: the system can handle multiple active independent or cooperating objects at the same time
--thread [of control]—models sequential execution of a set of instructions; embedded system may have several concurrent threads operating simultaneously
--persistence—how long does a software object last?
Examples:
Temporary variable
Global variable
Software module
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Recall: “UML” syntax can vary among implementations;
Previously we looked at one implementation, here we consider examples from the text
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UML: Use case diagram (graphical)
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UML Use case diagram--example
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UML: Use case diagram (text); note exceptions
UML—static modeling
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UML: Class diagram (“CRC card”)
Class name
data
Methods (responsibilitiesandcollaborators)
(+ collaborators)
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UML: class relationships: inheritance
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UML: “interface”—similar to inheritance but different
public appearance
Hidden operation
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UML: containment of one class within another
Type 1: aggregation—statistical analysis has a number of algorithm “parts”
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UML: containment of one class within another
Type 2: composition—here the intervals are meaningless outside the schedule (~ “local variables”)
UML—dynamic modeling
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UML: interaction diagram—call and return
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UML: interaction diagram—create and destroy
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UML: interaction diagram—send (no response expected)
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UML: sequence diagram:sequence of actions; carries out a use case
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UML sequence diagram--example
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UML: concurrent behavior. Example: fork and join
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UML: concurrent behavior. Example: branch and merge
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UML activity diagram—captures all actions and control flows within a task
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UML state machine models--4 types of events:
UML state chart is a directed graph
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UML state chart: types of transitions
initial state
final state
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UML state chart: actions and guard conditionsIf guard condition is false, transition does not happen
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UML: can decompose state into sequential substates
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UML: can define a “history” state (e.g., for an interrupt)—system will probably eventually return to this state
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UML: can have concurrent substates
UML is a tool for a structured design methodology
It helps manage the design and development process
We can also look at modifying / refining the PROCESS itself
"hardware / software life cycle": easier specify requirements (cheaper) (levels:1. functional to fix 2. performance mistakes (time/space) 3. implementation 4. use 5. maintenance)
analyze requirements design implement harder to fix test mistakes maintain
CMM : capability maturity model--defines level of the development process itself
1. Initial: ad hoc
2. Repeatable: basic project management processes in place
3. Defined: documented process integrated into an organization-wide software process
4. Managed: detailed measures are collected
5. Optimizing--desired level: Continuous process improvement from quantitative feedback
UML is a tool for a structured design methodology
It helps manage the design and development process
We can also look at modifying / refining the PROCESS itself
"hardware / software life cycle": easier specify requirements (cheaper) (levels:1. functional to fix 2. performance mistakes (time/space) 3. implementation 4. use 5. maintenance)
analyze requirements design implement harder to fix test mistakes maintain
CMM : capability maturity model--defines level of the development process itself
1. Initial: ad hoc
2. Repeatable: basic project management processes in place
3. Defined: documented process integrated into an organization-wide software process
4. Managed: detailed measures are collected
5. Optimizing--desired level: Continuous process improvement from quantitative feedback
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Another methodology: control flow and data flow diagrams(Note: in a processor we usually have a data path and a control path)
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Control and data flow diagrams: tasks (with hierarchy levels)
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Control and data flow diagrams: Data sources and sinks
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Control and data flow diagrams: Data stores
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Control and data flow diagrams: Example
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Control and data flow diagrams: Hierarchical view of an input / output task