So we beat on, boats against the current, borne back ceaselessly into the past.
于是我们继续奋力向前，逆水行舟，被不断地向后推，直至回到往昔岁月。
Sustainability is no longer optional—it’s a business imperative.
We are all in the gutter, but some of us are looking at the stars.
可持续性不再是可选项，而是任何想在21世纪蓬勃发展的企业的必需品。
在计算学习的背景下，“可能近似正确”（PAC）学习的概念为理解学习算法的效率和可行性提供了一个框架。