The system structure is a multilayer system structure with five layers. They are user interactive layer, system program interface layer, mining core service layer, data access layer, database layer.

系统使用五层体系结构，分别为：用户交互层，系统编程接口层，挖掘核心服务层，数据库访问层，数据库。

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The idea of working with a private equity company like Blackstone is that BHP would be able to take Alcoa's core mining and exploration assets and then carve off other, unwanted units for its partner.

FORBES: Magazine Article

The mining group has said that it wants to focus on core businesses such as iron ore and coal.

BBC: BHP Billiton sells Arizona copper mine to Capstone

To determine whether a deposit has enough of a mineral to merit mining, companies use air-based geological mapping and drill for core samples.

WSJ: Exhausting the Earth's Resources? Not So Fast