Software projects have a low success rate in terms of reliability, meeting due dates and working within assigned budgets with only 16% of projects being considered fully successful while Capers Jones has estimated tha...Software projects have a low success rate in terms of reliability, meeting due dates and working within assigned budgets with only 16% of projects being considered fully successful while Capers Jones has estimated that such projects only have a success rate of 65%. Many of these failures can be attributed to changes in requirements as the project progresses. This paper reviews several System Dynamics models from the literature and analyses the model of Andersson and Karlsson, showing that this model is uncontrollable and unobservable. This leads to a number of is-sues that need to be addressed in requirements acquisition.展开更多
Effectively managing the requirements and traceability in a complex software project can be a challenging task. Many tools exist to support the initial creation and management of changes to text-based requirements. Th...Effectively managing the requirements and traceability in a complex software project can be a challenging task. Many tools exist to support the initial creation and management of changes to text-based requirements. The most popular commercial solutions use a centralized server to host a database with a front-end desktop or web interface. Some downsides to this approach include user interface bloat, server costs, and an inherent disconnection from the project’s source files. To provide an alternative to traditional requirements management, Doorstop was created as a tool to allow requirements to be stored as text files in version control. This solution allows a project to utilize its existing development tools to manage versions of the requirements using a lightweight, developer-friendly interface.展开更多
In service-oriented computing, process model may serve as a link to connect users’ requirements with Web Services. In this paper, we propose an approach and related key techniques to generate process-oriented require...In service-oriented computing, process model may serve as a link to connect users’ requirements with Web Services. In this paper, we propose an approach and related key techniques to generate process-oriented requirements specification from user’s goal. For this purpose, a requirements description language named SORL will be provided to capture users’ requirements. Then, a unified requirements meta-modeling frame RPGS will be used to construct reusable domain assets, which is the basis of generating requirements specifications. Finally, a set of rules are defined to extract process control structures from users’ requirements described with SORL, so that we can convert requirements description into process-oriented requirements specification smoothly.展开更多
We apply the method of guidance by a required velocity for solving the optimal control problem over spacecraft’s reorientation from known initial attitude into a required final attitude.We suppose that attitude contr...We apply the method of guidance by a required velocity for solving the optimal control problem over spacecraft’s reorientation from known initial attitude into a required final attitude.We suppose that attitude control is carried out by impulse jet engines.For optimization of fuel consumption,the controlling moments are calculated and formed according to the method of free trajectories together with principle of iterative control using the quaternions for generating commands to actuators.Optimal solution corresponds to the principle“acceleration-free rotation-separate corrections-free rotation-braking”.Rotation along a hitting trajectory is supported by insignificant correction of the uncontrolled motion at discrete instants between segments of acceleration and braking.Various strategies of forming the correction impulses during stage of free motion are suggested.Improving accuracy of achievement of spacecraft's final position is reached by terminal control using information about current attitude and angular velocity measurements for determining an instant of beginning of braking(condition for start of braking based on actual motion parameters is formulated in analytical form).The described method is universal and invariant relative to moments of inertia.Developed laws of attitude control concern the algorithms with prognostic model,the synthesized control modes are invariant with respect to both external perturbations and parametric errors.Results of mathematical modeling are presented that demonstrate practical feasibility and high efficiency of designed algorithms.展开更多
文摘Software projects have a low success rate in terms of reliability, meeting due dates and working within assigned budgets with only 16% of projects being considered fully successful while Capers Jones has estimated that such projects only have a success rate of 65%. Many of these failures can be attributed to changes in requirements as the project progresses. This paper reviews several System Dynamics models from the literature and analyses the model of Andersson and Karlsson, showing that this model is uncontrollable and unobservable. This leads to a number of is-sues that need to be addressed in requirements acquisition.
文摘Effectively managing the requirements and traceability in a complex software project can be a challenging task. Many tools exist to support the initial creation and management of changes to text-based requirements. The most popular commercial solutions use a centralized server to host a database with a front-end desktop or web interface. Some downsides to this approach include user interface bloat, server costs, and an inherent disconnection from the project’s source files. To provide an alternative to traditional requirements management, Doorstop was created as a tool to allow requirements to be stored as text files in version control. This solution allows a project to utilize its existing development tools to manage versions of the requirements using a lightweight, developer-friendly interface.
文摘In service-oriented computing, process model may serve as a link to connect users’ requirements with Web Services. In this paper, we propose an approach and related key techniques to generate process-oriented requirements specification from user’s goal. For this purpose, a requirements description language named SORL will be provided to capture users’ requirements. Then, a unified requirements meta-modeling frame RPGS will be used to construct reusable domain assets, which is the basis of generating requirements specifications. Finally, a set of rules are defined to extract process control structures from users’ requirements described with SORL, so that we can convert requirements description into process-oriented requirements specification smoothly.
文摘We apply the method of guidance by a required velocity for solving the optimal control problem over spacecraft’s reorientation from known initial attitude into a required final attitude.We suppose that attitude control is carried out by impulse jet engines.For optimization of fuel consumption,the controlling moments are calculated and formed according to the method of free trajectories together with principle of iterative control using the quaternions for generating commands to actuators.Optimal solution corresponds to the principle“acceleration-free rotation-separate corrections-free rotation-braking”.Rotation along a hitting trajectory is supported by insignificant correction of the uncontrolled motion at discrete instants between segments of acceleration and braking.Various strategies of forming the correction impulses during stage of free motion are suggested.Improving accuracy of achievement of spacecraft's final position is reached by terminal control using information about current attitude and angular velocity measurements for determining an instant of beginning of braking(condition for start of braking based on actual motion parameters is formulated in analytical form).The described method is universal and invariant relative to moments of inertia.Developed laws of attitude control concern the algorithms with prognostic model,the synthesized control modes are invariant with respect to both external perturbations and parametric errors.Results of mathematical modeling are presented that demonstrate practical feasibility and high efficiency of designed algorithms.
