272 Personal Content Experience: Managing Digital Life in the Mobile Age available. Deleting can be for several reasons, such as the created object is not of satisfying quality or is no longer needed. Because delet- ing an object is a fi nal step, and can be done unintentionally, there are mechanisms that enable undoing the operation. Desktop comput- ers have a special folder called a trash bin or an equivalent, which stores deleted objects and also restores them if needed. Because this folder consumes storage space it can be emptied (semi)automatically. Compressing content is a method that speeds up any transfer pro- cesses, as well as saving storage space, if the system can provide enough memory and processing power to do it in real time. Otherwise it is advisable to do this operation while the device is in an idle state. The system can identify rarely-used content with the aid of metadata and compress it whenever in an idle state. Similarly, the system can anticipate user future actions based on their behaviour with the content objects and uncompress the content beforehand. In Chapter 4 we claimed that organizing content is one of the tasks that profi t from metadata, as it enables the user to interact with the view and change its contents dynamically. We presented a set of operations, such as grouping, fi ltering, and sorting, as examples. The true challenge of creating dynamic views based on metadata is to provide view controls that enable the user to manipulate the view quickly and effortlessly. The dynamic view should enable the user to explore a huge content set in such a way that they can generate different kinds of views in order to, for instance, benefi t of Gestalt laws and pick up new information, see an overview, identify clusters of related content, and so forth. Furthermore, the views should be formed in such a way that the user can understand what is presented and why. For example, what are the attributes used as a sorting key, and what attributes and range of values are used for fi ltering? Metadata can be used automatically and dynamically to create views where the use of the screen space is based on the amount and type of content. The user can then modify, for instance, the sorting key, defi ne what objects should be highlighted or fi ltered, or what attributes and values are displayed. Matrix Browser (discussed earlier in this section) could be used for exploring metadata of content objects as well as an interface for modi- fying the values. However, in some cases, the user may wish to describe which attribute a certain part of the object relates to. For instance, the user emphasizes or selects a portion of text or image and attaches a keyword to it. Even though metadata should be created largely through automa- tion, there are a few tasks that require manual entry, especially rating