Identifying all the users of data and their various needs is vitally important to the successful development and implementation of any data management plan. Given the interdisciplinary nature of much global change research, and the high cost of developing data sets, it is very likely that the user community will include not only existing study participants, but also additional future users. These future users may want to use the data for novel purposes and to interface them with data types beyond those originally envisioned. This requires defining user needs in the broadest sense possible. The term "user needs," as used here, refers to needs to find, evaluate, access, transfer, and/or combine data. It also refers to requirements for manipulating, processing, analyzing, or otherwise working with the data. Finally, it refers to the necessity for users to respond to institutional or cultural constraints, motivations, or pressures. Questions to consider include the following.

• Was there a clear definition of users and user groups at the inception of the research project?

• Were users at each step of the data path, from initial data collection to final analysis and archiving, clearly defined?

• Were the specific requirements of users at each step of the data path clearly defined?

• Were future potential users' needs predicted and accommodated?

• Were there incompatibilities or conflicts among different user groups?

• Were institutional structures and management mechanisms (committees, working groups) established to identify users' needs and resolve conflicts?

• Did users feel as if their needs were accommodated? If not, why not?

• Did the study create specialized algorithms, routines, data management procedures, or database structures to accommodate users' needs? If so, how successful were they?