使用规则引擎

Question

我有以下情况-

我有Company 和Incident。

Company 提供许多服务 (Service)，因此 - has_and_belongs_to_many :services。

Incident 需要一些服务 (Service)，因此 - has_and_belongs_to_many :services

现在，对于给定的事件，我需要找到所有提供我需要的服务的公司。我希望使用规则引擎来执行此操作，因为我有很多更复杂的条件要申请来选择合适的公司。

我研究了这个名为 - Wongi-engine (github.com/ulfurinn/wongi-engine) 的 gem，但是我很难把它包起来并编写规则。

你能给我一些建议吗？谢谢！

我可以想出以下facts：

engine << [ "CompanyA", "offers", "serviceA" ]
engine << [ "CompanyB", "offers", "serviceB" ]
engine << [ "CompanyA", "offers", "serviceB" ]
engine << [ "CompanyB", "offers", "serviceC" ]
engine << [ "IncidentA", "requires", "serviceC" ]
engine << [ "IncidentA", "requires", "serviceA" ]

编辑： 另外，一旦我编写了这些规则，如何使用 Rails 模型代替这些字符串？在 Ruby on Rails 应用程序的上下文中将事实加载到引擎中是否有任何最佳实践？

我的用例是，用户选择一个事件并询问可以为该事件提供服务的公司。我需要向规则引擎询问可以做到这一点的公司列表:)

Answer 1

您可以通过对引擎的嵌套迭代来做到这一点。

engine.each "IncidentA", "requires" :_  do |requires|
  engine.each :_, "offers", requires.object do |offers|
    puts "IncidentA can get #{requires.object} from #{offers.subject}"
  end
end

按照惯例这样做...

suppliers = engine.rule "service suppliers" do
    forall {
        has :Company, "offers", :Service
        has :Incident, "requires", :Service
    }
end

然后使用规则，选择事件类型并迭代信息。

suppliers.tokens.select{|s| s[:Incident] == "IncidentA" }.each do |s|
  puts "#{s[:Incident} can get #{s[:Service]} from #{s[:Company]}"
end

将其作为查询...

q = engine.query "companies" do
  search_on :Incident
  forall {
      has :Company, "offers", :Service
      has :Incident, "requires", :Service
  }
end

engine.execute "companies", { Incident: "IncidentA" }
q.tokens.each do |s|
  puts "#{s[:Incident} can get #{s[:Service]} from #{s[:Company]}"
end

编辑为您关于填充facts的问题添加注释...

假设您有Company 和name 属性Incident 和name 和Service 属性name

Company.joins(:services).select("companies.*, services.name as service_name").each do |company|
  engine << [company.name, "offers", company.service_name]
end

Incident.joins(:services).select("incidents.*, services.name as service_name").each do |incident|
  engine << [incident.name, "requires", incident.service_name]
end