0 at any time that someone wants or needs something -- 一经要求，在有需求时
1 available when a customer wants or asks for something -- 应顾客要求即可提供的，随选的
They will sell a voice recognition product as an add-on, on-demand service for their users. 他们会将一个语音识别系统作为附加的随选服务提供给用户。
In the library's warehouse, robots would manage stock and fetch books on an on-demand basis. 在图书馆仓库里，机器人会管理存贮并取出顾客随选的书。
Most people in this region do not even have television, let alone on-demand movies. 这个地区的大部分人连电视机都没有，更别说点播电影了。
2 a service for watching films or TV programmes at any time -- 视频点播服务
Teachers should be aware of the possibilities the online communities offer in terms of collaborative, on-demand based reciprocal learning, and social searching of information.
This is what we call the on-demand inference.
One problem with on-demand scenarios is that judgment has constrained the search area.
Since policy programs are separate from the system (and integrated only on-demand) they are a convenient means for imposing consistent security restrictions on multiple hosts.
Under ideal instrumental conditions, the modelling team should have on-demand remote access to the survey site on the basis of telepresence.
In fact, on-demand injections have been alleged to be inadequate as a standard of care for pain management.
We are concerned with the development of an on-demand transport system of driverless automatic taxis running on their own dedicated guideway network.
A standard way of accommodating infinite objects in programming (for example, in lazy functional languages) is to use generators and on-demand evaluation.
