"A lifestream is a time-ordered stream of documents that functions as a diary of your electronic life; every document you create and every document other people send you is stored in your lifestream. The tail of your stream contains documents from the past (starting with your electronic birth certificate). Moving away from the tail and toward the present, your stream contains more recent documents --- papers in progress or new electronic mail; other documents (pictures, correspondence, bills, movies, voice mail, software) are stored in between. Moving beyond the present and into the future, the stream contains documents you will need: reminders, calendar items, to-do lists.
You manage your lifestream through a small number of powerful operators that allow you to transparently store information, organize information on demand, filter and monitor incoming information, create reminders and calendar items in an integrated fashion, and "compress" large numbers of documents into overviews or executive summaries." (http://www.cs.yale.edu/homes/freeman/lifestreams.html)
David Gelernter at http://java.sun.com/developer/technicalArticles/Interviews/gelernter_qa.html
"I can imagine all the electronic information in my life collected into one beam, or (equivalently) one flowing stream. Every electronic document: every email, photo, draft, URL, audio, video, calendar or address note, and so on. Life is a series of events in time -- a timeline with a past, present and future. The events of your life and the memories in which they're recorded aren't parceled out into directories, or typed shoeboxes. An information beam incorporates documents of all types into one (focussable) beam. The question "where did I put that piece of information?" always has exactly one answer: it's in my beam.
The stream has a past, present and future. The future flows into the present into the past. If I've posted an appointment or reminder in the "future" part of the stream, eventually it flows automatically into the present where I'll notice it and be reminded, and then into the past where it's part of the permanent, searchable, browsable archive. When I acquire a new piece of "real-life" (versus electronic) information -- a new memory of (let's say) talking to Melissa on a sunny afternoon outside the Red Parrot -- I don't have to give this memory a name, or stuff it in a directory. I can use anything in the memory as a retrieval key. (I might recall this event when I think about Melissa, or sunny afternoons outside the Red Parrot.) I shouldn't have to name electronic documents either, or put them in directories. And I ought to be able to use anything in them as a retrieval key.
In our view of the future, users will no longer care about operating systems or computers; they'll care about their own streams, and other people's. I can tune in my stream wherever I am. I can shuffle other streams into mine -- to the extent I have permission to use other people's streams. My own personal stream, my electronic life story, can have other streams shuffled into it -- streams belonging to groups or organizations I'm part of. And eventually I'll have, for example, newspaper and magazine streams shuffled into my stream also. I follow my own life, and the lives of the organizations I'm part of, and the news, etc., by watching the stream flow." (http://java.sun.com/developer/technicalArticles/Interviews/gelernter_qa.html)