我将drools引擎插件添加到eclipse Kepler IDE中，然后我设置了它的所有首选项，但它在项目文件夹中给出了错误。请尽快回复我。
这是错误：
Exception in thread "main" java.lang.Error:
Unresolved compilation problems:
KnowledgeBase cannot be resolved to a type
The method readKnowledgeBase() from the type DroolsTest
refers to the missing type KnowledgeBase
StatefulKnowledgeSession cannot be resolved to a type
KnowledgeRuntimeLogger cannot be resolved to a type
KnowledgeRuntimeLoggerFactory cannot be resolved