A mathematician is preparing a module on adding two sine functions with the same frequency but different phases. She wants her students to appreciate the importance of this work for studying interference and would like some material written by a physicist that includes an interactive Java applet. A library search leads her quickly to the **Ripple Physlet**,
one of many excellent resources available at **WebPhysics** at Davidson College
http://webphysics.davidson.edu/welcome.htm

This physlet is designed to show wave interference effects. Click **edit** and then drag the sources to change their location. Then click **calculate** to restart the simulation.

Now the scenario becomes more interesting. The same mathematician is teaching the same course two years later and wants to use the same materials. She logs on with some trepidation. She has upgraded to new hardware, new software, and a new operating system; she remembers earlier experiences with broken links and disappearing sites. She does have the DOI or digital object identifier for the ripple applet and she knows that a DOI is associated with an object itself rather than its more ephemeral location like a URL.

She types in the DOI, -- "Eureka!" There it is -- and it still works. Furthermore, a window pops up reporting that this applet has been reviewed in several different publications and that several people have published electronic papers discussing how they've used it in their classes. She even sees a link to a short article she wrote reporting on her own use of the applet.

A high school physics teacher is looking for some interactive material on electrical circuits and Ohm's Law. A library search leads her to exactly what she wants at http://zebu.uoregon.edu/nsf/circuit.html. Like many high school physics teachers, she also teaches math classes and sees in this applet a nice lead-in to binary numbers.

A student working on a term paper needs information about air quality in Arizona. Going to the library, he finds a wealth of maps like http://www.epa.gov/region09/air/maps/az_pm10.html

A high school science teacher would like to investigate alcohol and driving in his classroom, but he has only limited equipment. He does a library search looking for "hits" whose requirements match the available equipment. He finds several possibilities including http://www.ti.com/calc/docs/act/cbl2_maturo1.htm

A calculus student is studying for a "gateway" exam that will test her ability to do routine differentiation. She wants to work a lot of problems and get immediate feedback. A virtual librarian who studied calculus the previous semester suggests that she visit http://www.math.temple.edu/~cow/index.html where she finds exactly what she was looking for. The next day she aces her exam.

A professor of Botany has a great idea for a new course. Before beginning to write a grant proposal seeking funds for his idea, he visits the library and discovers that his idea is not entirely new. Several courses have been developed based on similar ideas. He finds materials for those courses, and he finds reports of other professors' experiences with the courses. He introduces himself via email to several people who have worked on related ideas and arranges to have lunch with three of them at a professional meeting. He eventually submits a proposal building on work that has gone before. The proposal is funded and his project is a huge success.