In theory, software product lines are planned in advance, using established engineering methods. However, there are cases where commonalities and variabilities between several systems are only discovered after they have been developed individually as single systems. In retrospect, this leads to the hindsight that these systems should have been developed as a software product line from the beginning to reduce costs and effort. To cope with the challenge of detecting variability early on, we propose the PREVISE method, covering domain and application engineering. Domain engineering is concerned with exploring the variability caused by entities in the environment of the software and the variability in functional and quality requirements. In application engineering, the configuration for a concrete product is selected, and subsequently, a requirement model for a concrete product is derived.
Existing fair exchange protocols usually neglect consideration of cost when assessing their fairness. However, in an environment with non-negligible transaction cost, e.g., public blockchains, high or unexpected transaction cost might be an obstacle for wide-spread adoption of fair exchange protocols in business applications. For example, as of 2021-12-17, the initialization of the FairSwap protocol on the Ethereum blockchain requires the selling party to pay a fee of approx. 349.20 USD per exchange. We address this issue by defining cost fairness, which can be used to assess two-party exchange protocols including implied transaction cost. We show that in an environment with non-negligible transaction cost where one party has to initialize the exchange protocol and the other party can leave the exchange at any time cost fairness cannot be achieved.
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