Apps that know what you want, before you do

In Hollywood, there are umbrella holders. Outside corner offices, there are people who know exactly how much cream to pour in the boss's coffee. And then there is Silicon Valley, where mind-reading personal assistants come in the form of a cellphone app.

A range of start-ups and big companies like Google are working on what is known as predictive search — new tools that act as robotic personal assistants, anticipating what you need before you ask for it. Glance at your phone in the morning, for instance, and see an alert that you need to leave early for your next meeting because of traffic, even though you never told your phone you had a meeting, or where it was.

The technology is the latest development in web search, and one of the first that is tailored to mobile devices. It does not even require people to enter a search query. Your context — location, time of day and digital activity — is the query, say the engineers who build these services.

Many software programmers have dreamed of building a tool like this for years. The technology is emerging now because people are desperate for ways to deal with the inundation of digital information, and because much of it is stored in the cloud where apps can easily access it.

The goal is to move beyond logistical help to sending you anything you might need to know.