18. Consider the relation schema CLASS with attributes Student, Subject, and Teacher. The meaning of this relation is that the specified student is taught the specified subject by the specified teacher. Assume that semantic rules, depicted by the following functional depen- dencies, exist: {Student, Subject} → Teacher Teacher → Subject Subject A Teacher {Student, Teacher} → Subject а. What do these rules mean in words? Are all these rules necessary? If not, explain which are not needed. b. Is the following sample data consistent with these rules? Why or why not? Student Subject Teacher Smith Math White Smith Physics Green Jones Math White Jones Physics Brown С. What causes CLASS to contain a BCNF violation? What anomalies does it exhibit? d. Decompose CLASS if necessary so that the resulting relational schema is in BCNF. Is your design attribute-preserving, dependency-preserving, and a lossless-join decompo- sition? Exnlain

18. Consider the relation schema CLASS with attributes Student, Subject, and Teacher. The meaning of this relation is that the specified student is taught the specified subject by the specified teacher. Assume that semantic rules, depicted by the following functional depen- dencies, exist: {Student, Subject} → Teacher Teacher → Subject Subject A Teacher {Student, Teacher} → Subject а. What do these rules mean in words? Are all these rules necessary? If not, explain which are not needed. b. Is the following sample data consistent with these rules? Why or why not? Student Subject Teacher Smith Math White Smith Physics Green Jones Math White Jones Physics Brown С. What causes CLASS to contain a BCNF violation? What anomalies does it exhibit? d. Decompose CLASS if necessary so that the resulting relational schema is in BCNF. Is your design attribute-preserving, dependency-preserving, and a lossless-join decompo- sition? Exnlain

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Please answer 1a, 1b, and 2. questions attached
Draw dependency graphs corresponding to grammar rule of exp ->exp / exp | num | num.num for the expression 7/4/3.0 Describe the two passes needed to compute the attributes on the syntax tree of 7/4/3.0, including a possible order in which the nodes could be visited and the attribute values computed at each point.
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(a) Consider the following context free grammars (CFG): i. ii. B> dBb | bBd | dCb C>aC |E E>FG F> fgFg | fgGg |f G→ g Do left factoring of the above grammars (if necessary). Why is it needed to do left factoring of a grammar? Explain with proper example. (b) Write down the regular expression and draw the transition diagram of how a lexical analyzer will detect all the positive or negative floating point numbers (eg. 1.5, 45, 2. , - 98. , – 6.71,- .39 etc.). 2.
The discussion in questions 1 (a) and 1 (b) should incorporate whether and how predicate calculus can be implemented as a deep structure in question-answering programs. a) Discuss about TWO (2) several possible ways of using predicate calculus and argues that predicate calculus has significant advantages above competing deep structures if the way of using it is carefully selected. b) Based your answer on 1 (a), depict on how various predicate calculus can be encoded in a consistent way. c) Explain how axiom sets that define these encodings can be written and debugged.
5. Show that the CFG given below is ambiguous using derivations and parse trees: (Note: or, and, not, true, false are terminals) E > E or E E> E and E E → not E E> true E→ false
Discrete Structures or Discrete Mathematics
In attributed grammars what is an attribute computation function? A function associated with a production rule used to compute the value of an attribute. A function associated with a production used to check the value of an attribute. A function associated with a symbol used to check the value of an attribute. A function associated with a symbol used to compute the value of an attribute.
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