Architecture Modeling - SPES 2020

ReusableElement
ComData
+com Data 1
+referencedPorts
0..*
PortReference
Signal
+ length: int
Message
+ length: int
Frame
+ length: int
Architecture Modeling
+signal
1
+owner +signalT oMsgMapping
+message
1
+owner +msgT oFrameM apping
NamedElement
MsgToFrameMapping
0..*
+ offsetInFrame: int
0..*
«enumeration»
TransferPropertyKind
«enum eration»
triggered
pending
triggeredOnChange
SignalToMsgM apping
NamedElement
+ offsetInMessage: int
+ transferProperty: T ransferPropertyKind
Figure 3.16: Meta-model integration of the concepts for modeling data encapsulation
interface (API) is provided, that hides the complexity of different bus technologies and communication
protocols. Data sent by some application task is then processed by a communication
stack, which is typically organized in layers like in the Open Systems Interconnection model
(OSI) [51].
Beside the wish to abstract from the details of a layer of communication protocols from the
logical perspective of the system, in the technical perspective one needs a specification of e. g.
their real-time aspects or safety aspects. This allows to reason about whether requirements on
the communication of components in the logical perspective can be fulfilled when allocating
them to a technical architecture. Figure 3.16 shows the concepts of the meta-model, which
allow to capture the data encapsulations done by a communication stack and Figure 3.17 shows
their intended usage. For the sake of brevity the SchedulerSlots and a Scheduler are
not shown in that figure.
ComputingResource
header
header
app-task1:Task
app-task2:Task
Signal1
com:Task
Signal2
Signal1 Signal2
payload
Message1 Frame1
Message1
payload Frame1
bus-drv:Task
Figure 3.17: Example for specifying the data enscapsulation
The Signal concept represents data sent by some application tasks, which components
from the logical perspective have been allocated to. The declared Signal references Ports
in the technical architecture model to indicate at which ports it is sent or received. The concepts
Message and Frame also allow to reference multiple Ports. The data encapsulation by a
communication stack as sketched in the bottom half of Figure 3.17 is expressed by the concepts
SignalToMsgMapping and MsgToFrameMapping. They allow to describe the composition
of messages in frames and of signals in messages. The condition when a Task, which is
responsible for the encapsulation of Signals in Messages, actually triggers the Message
can be defined by the attributes of the concept SignalToMsgMapping. For example some
Signals mapped to the same Message may cause it to be triggered, while others just update
the value inside the Message.
26/ 156