Peer-to-peer systems typically depend on untrusted and volatile computer systems for most of
their resources. Trust is a social phenomenon with technical consequences. Volatility (i.e.
unpredicatable availability) also is often due to human actions. Elaborate your answers to Exercise
10.4. by discussing the possible ways in which each of them is likely to differ according to the
following attributes of the computers used:
i) ownership
ii) geographic location
iii) network connectivity
iv)country or legal jurisdiction
What does this suggest about policies for the placement of data objects in a peer-to-peer storage service?
What will be an ideal response?
ownership The owner of a computer is likely to act in a manner that maximizes his benefit, regardless of
the fact that some of its resources are shared by others. The notion of trust is relative to ownership, so actions
of type (b) or even (c) may be classified as acceptable.
geographic location Computers are subject to events of type (a) according to their geographic location.
network connectivity Portions of a network may become separated, making communication between them
impossible. This might enable the owners in a disconnected portion to act against the interest of the majority.
country or jurisdiction The affects the ‘freedom of speech’ issue since governments or courts may
persecute the owners of information or order the deletion of data. The latter can be addressed by ensuring that
there are replicas in several countries/jurisdictions.
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Answer the following statements true (T) or false (F)
1. An entity sub type is an entity that is used to represent a many-to-many relationship. 2. An associative entity is used for repeating groups. 3. Many data items can be packed into a field; the field can be read and converted to a number of data items. 4. A primary key is one of the data items in a record that uniquely identifies a record.
Practicing good, standard-based Web design means using HTML to define a document's structure and using ____ to control its presentation by defining visual properties.
A. XHTML B. CSS C. Java D. a graphics program
Presentation dynamics are the visual and audio aids that you display to support your points. ____________________
Answer the following statement true (T) or false (F)
An outside contractor is hired to perform a business impact analysis of a simulated disaster. The contractor asks stakeholders what they think a hurricane would do to the business. This is an inadequate method because:
A. the question is related to disaster recovery, not impact analysis B. the question is subjective and does not represent a complete business impact analysis C. it is impossible to perform an impact of anything simulated D. hurricanes vary in intensity, so the business impact is always unknown