某企业集团有若干工厂，每个工厂生产多种产品，且每一种产品可以在多个工厂生产，每个工厂按照固定的计划数量生产产品，计划数量不低于300；每个工厂聘用多名职工，且每名职工只能在一个工厂工作，工厂聘用职工有聘期和工资。工厂的属性有工厂编号、厂名、地址，产品的属性有产品编号、产品名、规格，职工的属性有职工号、姓名、技术等级（初级、中级、高级）。(A group has several factories, each plant produces a variety of products, and each product can be produced in a factory, the factory in accordance with each fixed quantity in the production plan, plan the number of not less than 300; each facility employs several employees, and each employee can only work in a factory, the factory workers employment duration of employment and wages. The attributes of the factory include the plant number, factory name and address. The attributes of the product include product number, product name and specification. The attributes of the staff include worker number, name and technical level (primary, intermediate, advanced).)