254 Personal Content Experience: Managing Digital Life in the Mobile Age based on certain guidelines (heuristics), point out possible problems, and suggest improvements; and usability testing, where the test sub- jects perform a set of test tasks with the application while being observed. There are also a myriad of additional methods that are useful and important. It is crucial to understand that often selecting a usability test method does not rule out using other techniques. Furthermore, the designers should set usability metrics, where they describe the target level for the usability in terms of desired values for the above-mentioned attributes. In addition, the worst and the best case values should also be defi ned. 6.5 Performing the GEMS Tasks We have illustrated various aspects related to interacting with the device in general. Now we discuss how they relate to various GEMS tasks. Furthermore, we describe what kinds of steps are required in the tasks, and how to use different views and controls in order to aid the user in reaching a desired goal. 6.5.1 Cross-GEMS Tasks: Browse and Search Before performing any GEMS actions on a content object, it must be fi rst located. There are two ways to do this: either browse or search. Which one to use depends on whether the user knows where the desired content object is stored and how to access it. If the user knows the location, they can browse (or perform implicit search), otherwise they need to (explicitly) search for the object. However, because the search result set typically contains more than one result, the user still needs to browse. These two are frequent tasks that need to be per- formed before executing tasks at later phases. If the user cannot explicitly name or locate the desired item, they must start searching.14 Searching is performed either in real time, or it is made against a pre-indexed database. In addition, some systems, such as peer-to-peer networks, do not maintain directories of the content they contain, which means that the user cannot browse the content without searching fi rst. 14 But then again, Google desktop search is used for accessing local content instead of browsing, even though the location and the name of the desired fi le is known. Typing a (partial) fi lename in the text box is considered faster than navigating in a fi le browser.