@MastersThesis{Hebig2009,
AUTHOR = {Hebig, Regina},
TITLE = {{Modeling of Feedback in Self-Adaptive Systems}},
YEAR = {2009},
MONTH = {October},
SCHOOL = {Hasso-Plattner-Institut f\"{u}r Softwaresystemtechnik, Universit\"{a}t Potsdam},
PDF = {uploads/pdf/Hebig2009_Thesis.pdf},
ABSTRACT = {Today, software often runs as embedded systems in mobile devices or distributed over
networks. Thus, a software system has to deal with changing demands and uncertainties
in the environment. Within embedded systems disturbances from the environment have
to be expected. Through the distribution over several devices, not only non-functional
properties, like the load of a service, may change, but also the interacting system parts
may be substituted during run-time.
Feedback, as it is used in control theory, deals with uncertainties and compensation of
disturbances. In software control loops can be used in order to implement self-adaptation,
self-healing, or self-optimization. The feedback, which is used in control loops, also oers
the possibility to deal with disturbances that stem from the environment of the software.
Although feedback is often implemented in software there is currently no support for an
explicit modeling of control loops in software. Without explicit models the interaction of
control loops cannot be shown. So an analysis of the structure and behavior of control
loops within complex systems is almost impossible.
This thesis introduces modeling concepts for the explicit modeling of feedback. Thereby
the concept of feedback is not only transferred from control theory to software, but also
supplemented with concepts that satisfy special needs of software. The introduced modeling
concepts are formalized in an UML prole. The presented concepts additionally enable the
design of control loops that apply structural adaptations to software systems. Through the
formulation of warning signal for control loops that are not well-formed, this thesis creates
the basis for the analysis of the interaction of control loops.}
}