The leading platforms in modern software development for applicationswith the user
interface are web and mobile platforms. In the earlier days, itwas common that the
purpose of the client side of these applications only dis-play data and process interactions,
while the backend ran all business logic inthe background. Recently a new trend can
be identified that the client appsinclude complex business logic as well. Modern web
frameworks and mobiletechnologies rely on the client device’s computing capacities
for the maximalperformance, therefore provide built-in services to cache data and
run stepsof the business logic on the client device. This paradigm is illustrated
by thesuccess of PWA technology and by offline applications. The user interface ofmodern
applications is designed by UX designers, who focus rather on theease of use and user
experience then safety and soundness, which often leadsto disrupting the well-defined
business process by introducing new sub-stepsand alternative ways. These tendencies
altogether result that the client-sideof modern applications also implement a lot
of business logic that alreadyimplemented by the backend in a more strict, straightforward
approach. Ina more abstract approach, the client and the server work with the same
typeof documents by performing two different business processes that exist atthe same
time. The two layers of the application are often developed bydifferent teams, where
frontend and backend specialists work simultaneously.Altogether this results in new
risks that should be mitigated by continuouslyevaluating the consistency of the two
business processes during the wholedevelopment life-cycle. This evaluation should
identify if the two processes are consistent, special tools have to be introduced
that ensure that after per-forming a particular iteration in the development roadmap,
the consistencyis still maintained. The goal of this paper is to introduce a formal
model forthis evaluation and introduce tools that can be derived from this model andcan
be used in software development and testing
