Architecture Modeling - SPES 2020

Architecture Modeling
The constraint consists of a constant phrase (denoted by the bold text) and a left and right
side. On the left side a conjunction of elements from the logical perspective are named (here:
LSI1 and LSI2). Their mapping is constraint with respect to the element(s) from the technical
perspective on the right side of the pattern (here: ECU-Instance).
Based on these constraints other constraints for the connected sensors of each system can
be derived. To ensure independence of the duplicated systems, each of their sensors must not
be shared between them. In our example sensors are assumed to be a exclusive resources, so
sharing is not allowed and no additional independence constraints are needed.
Technical Perspective On the technical perspective the airbag systems needs to be allocated
to ECUs and sensors. In our example we have four ECUs available, which are all of the same
type “ECU Type”. Each ECU instance has a series of ports with an incoming direction modeling
the possibility to connect equipment to them.
In the same way acceleration and pressure sensors are modeled. They have a base type (one
for acceleration and one for pressure sensing) and ports with an outgoing direction.
All ports are typed by a PortSpecification. Together with the direction information it is therefore
known which components can be connected. Such a connection between an ECU and a
sensor represents a cable in the airbag example. It is also possible to model the cable explicitly
with a separate component, which allows to specify additional properties, but in our example
the representation by connections is sufficient.
The mapping between elements of the logical and technical perspective can be done by
adding links to the model. This allocation can be used to formulate a mapping
problem or a solution. By allocating a logical sensor element on a technical sensor type
(e.g. “Acceleration Sensor Left Type”) the mapping problem to find a suitable sensor instance
of this type is specified. Alternatively the allocation target can already be a instance in which
case the allocation models a concrete mapping, i.e. a mapping solution.
In our airbag system the sensor systems are mapped to the corresponding sensor type in the
technical perspective. This way a problem space is created. Since two pressure and acceleration
sensors are available on each side the optimal one depends on the allocation of the systems to
the ECUs. Also the computational parts can be executed on any of the available ECUs. Thus
the allocation of the LSI, RSI and FI systems to ECUs is an open mapping problem. A solution
to such a problem must fulfill all needed sensor inputs of the subsystem and the independence
constraints associated with the system. By connecting ports of sensors with ports of an ECU a
cable is added to the system. To be able to calculate the resulting cable length the geometrical
perspective is used.
Geometrical Perspective The geometrical perspective is used to organize the information
regarding the position of the ECUs, the positions of the Sensors and the distance between these
elements. The distance is determined by the actual cabling in the car, i.e. that the distance is
influenced by the physical environment of the vehicle. Some cable can be put through the roof
of the vehicle directly while other cables have to be put through the vehicle chassis. This can
lead to a very different cable length from two nearby sensors to an ECU a fact which underline
the importance of the automation of the optimization process, since the obvious solutions are
most probably not the optimal ones.
Model Processing As stated above the allocation links between the logical and the technical
perspective are capable of creating an allocation space. The geometrical perspective provides
the information to evaluate the different possibilities to solve the allocation. Furthermore the
31/ 156