1) All figures in the doc are available as high-res images upon mouse
click, but this functionality is not available by keyboard. E.g. <img
This should be made an <a> element to allow for keyboard interaction.
There are Web users who use no mouse, but would like to see the images
in high resolution. Also, all figures lack a long description.
2) The most interesting part for PF is the context object. However, the
doc contains no specification for context. In , context data is
simply not defined: "The format and meaning of this data is
application-specific." If  was to be revised, it would be good to
provide examples of context data which can be used to define a user's
preferences (e.g. pointer to a GPII personal preference set), a device's
characteristics, and situational parameters. However, it is not clear
if the context data could also include information on dynamic aspects of
the interaction, e.g. a sudden increased noise level around the user.