One of the important topics in knowledge base revision is to introduce an efficient implementation algorithm. Algebraic approaches have good characteristics and implementation method; they may be a choice to solve the problem. An algebraic approach is presented to revise propositional rule-based knowledge bases in this paper. A way is firstly introduced to transform a propositional rule-based knowledge base into a Petri net. A knowledge base is represented by a Petri net, and facts are represented by the initial marking. Thus, the consistency check of a knowledge base is equivalent to the reachability problem of Petri nets. The reachability of Petri nets can be decided by whether the state equation has a solution; hence the consistency check can also be implemented by algebraic approach. Furthermore, al-gorithms are introduced to revise a propositional rule-based knowledge base, as well as extended logic programming. Compared with related works, the algorithms presented in the paper are efficient, and the time complexities of these algorithms are polynomial.
利用Eye Link II眼动仪视频叠加的方法,记录12名大学生被试操作虚拟现实软件过程中的行为和眼动指标,考察了被试在化身和方向键两种版本的桌面虚拟现实系统中的浏览行为。结果表明,化身组和方向键组的被试在浏览时间、注视点总数、平均注视时间上无显著差异;方向键组被试比化身组被试更多地注视操作区域(化身或方向键),意味着方向键版本需要更多的操作和控制;化身组和方向键组被试都表现出明显的学习效应。本研究表明眼动视频叠加是评估虚拟现实系统有效手段。
