Represent the Is A hierarchy, in the relational model. For each Is A relationship discuss your choice of the representation technique Discuss the circumstances in which an alternative representation (to the one you have chosen) would be better.
What will be an ideal response?
To represent the relationship IsA Employee, we would add an additional status attribute to the schema of Employee. This is because the entity types Secretary and Technician are likely to be disjoint. Similar considerations apply to IsA Student.
The downside of this representation is that some tuples will have null values over the attribute Specialization (in case of secretaries) and Major and Advisor (in case, say, of freshmen).
The relationship IsA Person is di?erent from the above two in that its subentities, Employee and Student, can have fairly large intersection. Thus, to avoid the duplication associated with the use of the Status attribute, we would use three relations, Person (SSN,Name,DOB), Employee (SSN,Department,Salary), and Student (SSN,GPA,StartDate).
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A(n) ____________ specifies a variable’s name and data type.
a. variable declaration b. data indicator c. object tag d. source entity
Each of many sensor nodes are to be scattered throughout a region. The nodes are to communicate securely. Explain the problem of key distribution and outline a probabilistic strategy for distributing keys.
What will be an ideal response?
Text boxes can also be referred to as word frames.
Answer the following statement true (T) or false (F)
Identify the letter of the choice that best matches the phrase or definition.
A. The colors that make up a gradient B. A set of 12 preset adjustments that affect the brightness and contrast of a layer style to create dramatic lighting effects C. The layer that functions as the clipping mask D. To convert to pixels E. Using artwork on one layer to mask the artwork on a layer above it