In order to guarantee transaction timeliness, Realtime Database Management Systems (RTDBMSs) often relax data consistency by relaxing the ACID transaction properties. Such relaxation varies depending on the application and thus different transaction management mechanisms have to be decided for developing a tailored RTDBMS. However, current RTDBMSs development does not include systematic verification of timeliness and desired ACID properties. Consequently, the implemented transaction management mechanisms may breach timeliness of transactions. In this paper, we propose a process called DAGGERS for developing a tailored RTDBMS that guarantees timeliness and desired data consistency for real-time systems by employing model-checking techniques during the process. Based on the characteristics of the desired data manipulations, transaction models are designed and then formally verified iteratively together with selected run-time mechanisms, in order to achieve the desired/necessary trade-offs between timeliness and data consistency. The outcome of DAGGERS is thus a tailored transaction management with guaranteed appropriate trade-offs, as well as the model-checking based worst-case execution times and blocking times of transactions under these mechanisms and assumptions of the hardware architecture.