1、建立推理规则库

首先，建立规则库（知识库），本实验系统部分规则如下：

① 哺乳动物食肉动物黄褐色黑色条纹虎

② 鸟长脖子长腿黑白二色不飞鸵鸟

2、输入事实进行推理

输入事实后开始推理：

3、推理结果

输入规则①推理事实，显示推理结果如图2所示。

■ 图2 规则①推理结果

输入规则②推理事实，显示推理结果如图3所示。

■ 图3规则②推理结果

实践对应示例程序参见附录C。

附录C 基于规则产生式的推理

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import (QWidget, QHBoxLayout, QLabel, QApplication)
from PyQt5.QtGui import QPixmap
import sys
class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.setGeometry(100, 200, 623, 300)
        self.groupBox = QtWidgets.QGroupBox(Form)
        self.groupBox.setGeometry(QtCore.QRect(10, -20, 700, 311))
        self.groupBox.setTitle("")
        self.groupBox.setObjectName("groupBox")
        self.label = QtWidgets.QLabel(self.groupBox)
        self.label.setGeometry(QtCore.QRect(30, 40, 61, 18))
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.groupBox)
        self.label_2.setGeometry(QtCore.QRect(470, 40, 101, 18))
        self.label_2.setAlignment(QtCore.Qt.AlignCenter)
        self.label_2.setObjectName("label_2")
        self.pushButton = QtWidgets.QPushButton(self.groupBox)
        self.pushButton.setGeometry(QtCore.QRect(230, 35, 88, 27))
        self.pushButton.setObjectName("pushButton")
        self.pushButton_3 = QtWidgets.QPushButton(self.groupBox)
        self.pushButton_3.setGeometry(QtCore.QRect(475, 265, 88, 27))
        self.pushButton_3.setObjectName("pushButton_3")
        self.pushButton_3.clicked.connect(QtCore.QCoreApplication.instance().quit)
        self.textEdit = QtWidgets.QTextEdit(self.groupBox)
        self.textEdit.setGeometry(QtCore.QRect(20, 80, 80, 211))
        self.textEdit.setObjectName("textEdit")
        self.textEdit_2 = QtWidgets.QTextEdit(self.groupBox)
        self.textEdit_2.setGeometry(QtCore.QRect(110, 80, 331, 211))
        self.textEdit_2.setObjectName("textEdit_2")
        self.textEdit_2.setReadOnly(True)
        self.lineEdit = QtWidgets.QLineEdit(self.groupBox)
        self.lineEdit.move(450, 80)
        self.lineEdit.setGeometry(QtCore.QRect(450, 80, 140, 40))
        self.lineEdit.setReadOnly(True)
        self.pushButton.clicked.connect(self.go)

        self.label_3 = QtWidgets.QLabel(self.groupBox)
        self.label_3.setGeometry(QtCore.QRect(450, 125, 140,140))
        self.label_3.setAlignment(QtCore.Qt.AlignCenter)
        self.label_3.setObjectName("label_3")

        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)


    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "正向推理-动物识别系统"))
        self.label.setText(_translate("Form", "输入事实"))
        self.label_2.setText(_translate("Form", "显示推理结果"))
        self.label_3.setText(_translate("Form", ""))
        self.pushButton.setText(_translate("Form", "进行推理"))
        self.pushButton_3.setText(_translate("Form", "退出程序"))

    # 将知识库做拓扑排序
    def topological(self):
        Q = []
        P = []
        ans = ""  # 排序后的结果
        for line in open('RD.txt'):
            line = line.strip('\n')
            if line == '':
                continue
            line = line.split(' ')
            Q.append(line[line.__len__() - 1])
            del (line[line.__len__() - 1])
            P.append(line)

        # 计算入度
        inn = []
        for i in P:
            sum = 0
            for x in i:
                if Q.count(x) > 0: # 能找到，那么
                    sum += Q.count(x)
            inn.append(sum)

        while (1):
            x = 0
            if inn.count(-1) == inn.__len__():
                break
            for i in inn:
                if i == 0:
                    str = ' '.join(P[x])
                    ans = ans + str + " " + Q[x] + "\n"  # 写入结果
                    inn[x] = -1
                    # 更新入度
                    y = 0
                    for j in P:
                        if j.count(Q[x]) == 1:
                            inn[y] -= 1
                        y += 1
                x += 1
        print(ans)

        # 将结果写入文件
        fw = open('RD.txt', 'w', buffering=1)
        fw.write(ans)
        fw.flush()
        fw.close()

    # 进行推理
    def go(self, flag=True):
        # 将产生式规则放入规则库中
        # if P then Q
        # 读取产生式文件
        self.Q = []
        self.P = []
        fo = open('RD.txt', 'r', encoding='utf-8')
        for line in fo:
            line = line.strip('\n')
            if line == '':
                continue
            line = line.split(' ')
            self.Q.append(line[line.__len__() - 1])
            del (line[line.__len__() - 1])
            self.P.append(line)
        fo.close()
        self.lines = self.textEdit.toPlainText()
        self.lines = self.lines.split('\n') # 分割成组
        self.DB = set(self.lines)
        print(self.DB)
        self.str = ""
        print(self.str)
        flag = True
        temp = ""
        for x in self.P:  # 对于每条产生式规则
            if ListInSet(x, self.DB): # 如果所有前提条件都在规则库中
                self.DB.add(self.Q[self.P.index(x)])
                temp = self.Q[self.P.index(x)]
                flag = False # 至少能推出一个结论
                self.str += "%s --> %s\n" % (x, self.Q[self.P.index(x)])

        if flag:  # 一个结论都推不出
            print("无法推出结论")
            for x in self.P:  # 对于每条产生式
                if ListOneInSet(x, self.DB): # 事实是否满足部分前提
                    flag1 = False # 默认提问时否认前提
                    for i in x:  # 对于前提中所有元素
                        if i not in self.DB:  # 对于不满足的那部分
                            btn = s.quest("是否" + i)
                            if btn == QtWidgets.QMessageBox.Ok:
                                self.textEdit.setText(self.textEdit.toPlainText() + "\n" + i) # 确定则增加到textEdit
                                self.DB.add(i) # 确定则增加到规则库中
                                flag1 = True # 肯定前提
                                # self.go(self)
                    if flag1:  # 如果肯定前提，则重新推导
                        self.go()
                        return

        self.textEdit_2.setPlainText(self.str)
        print(self.str)
        if flag:
            btn = s.alert("没有推出任何结论")
        else:
            self.lineEdit.setText(temp)
            self.label_3.setPixmap(QPixmap(temp+'.jpg'))
            self.label_3.setScaledContents(True)

            # 判断list中至少有一个在集合set中
def ListOneInSet(li, se):
    for i in li:
        if i in se:
            return True
    return False


# 判断list中所有元素是否都在集合set中
def ListInSet(li, se):
    for i in li:
        if i not in se:
            return False
    return True


class SecondWindow(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(SecondWindow, self).__init__(parent)
        self.setGeometry(725, 200, 300, 300)
        self.textEdit = QtWidgets.QTextEdit(self)
        self.textEdit.setGeometry(8, 2, 284, 286)


    # 警告没有推导结果
    def alert(self, info):
        QtWidgets.QMessageBox.move(self, 200, 200)
        QtWidgets.QMessageBox.information(self, "Information", self.tr(info))

    # 询问补充事实
    def quest(self, info):
        # 如果推理为空，需要询问用户是否要添加已知条件
        QtWidgets.QMessageBox.move(self, 200, 200)
        button = QtWidgets.QMessageBox.question(self, "提示",
                                                self.tr(info),
                                                QtWidgets.QMessageBox.Ok | QtWidgets.QMessageBox.Cancel,
                                                QtWidgets.QMessageBox.Cancel)
        return button

if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    widget = QtWidgets.QWidget()
    ui = Ui_Form()
    ui.setupUi(widget)
    widget.show()
    s = SecondWindow()
    sys.exit(app.exec_())