We described several technologies that provide receive-constrained channels for use in secure
spontaneous device association. Which of those technologies also provide send-constrained
channels?
What will be an ideal response?
Physical contact. Clearly this also provides send-constrained channels.
Infrared. By default, this provides us with a channel that is send-constrained only up to the boundary of a room,
say, since an infrared receiver on, say, a PDA or mobile phone could receive data from many possible sources.
However, it is possible to mount a receiver behind a lens to prevent signals from sources outside a required
direction.
Audio. This provides us with a channel that is send-constrained only up to the boundary of an insulated room,
say, since received audio could emanate from many possible sources.
Laser. By default, this provides us with a channel that is send-constrained only up to the nearest optical barrier.
However, by mounting a receiver at the end of a narrow, opaque, non-reflective tube one could limit sources
to lie in a given direction.
Barcode and camera. This combination can provide useful send-constrained channels. A camera can be
focused and positioned so as to read data only from symbols presented from a given orientation and distance.
For example, a user can place her camera phone so as to be sure of reading just the symbol presented by a given
device.
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Identify all the important concepts represented in the library database case study described here. In particular, identify the abstraction of classification (entity types and relationship types), aggregation, identification, and specialization/generalization. Specify (min, max) cardinality constraints whenever possible. List details that will affect the eventual design but which have no bearing on the conceptual design. List the semantic separately. Draw an EER diagram of the library database.
What will be an ideal response?
Embedding fonts in a presentation ensures that the font will display properly on any computer
Indicate whether the statement is true or false
______________________________________ are the two data processing approaches used in modern systems.
What will be an ideal response?