Aerial photo shows a staff member picking vegetables in Tongren, southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students. (Photos: Xinhua)

Students have lunch at No.11 Primary School of Tongren City in southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.

A staff member shows newly-picked vegetables in Tongren, southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.

Students queue up for lunch at No.11 Primary School of Tongren City in southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.

Staff members prepare lunch for students at No.11 Primary School of Tongren City in southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.

A staff member introduces a big data-based monitoring system in Tongren, southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.

Students have lunch at No.11 Primary School of Tongren City in southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.

Staff members check information of received ingredients through a big data-based system at No.11 Primary School of Tongren City in southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.

A staff member prepares lunch for students at No.11 Primary School of Tongren City in southwest China's Guizhou Province, May 21, 2019. Tongren City has established a monitoring system applying new technologies of big data to trace food from farming to dining table, an effort to guarantee food safety for students.