Generate a CFG for the following expression: a*bambmc Where n>0, m>=0

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
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Generate a context free grammer for the expression, your final answer should be in a similar form to the red circled example. 

**Title: Understanding Grammar for (a^n b^a)^*, Where n ≥ 2**

**Introduction:**

In formal language theory, we often explore grammars that generate particular patterns of strings. One such pattern is (a^n b^a)^*, where n is greater than or equal to 2. Let's explore the rules and an example of how such a grammar can be constructed.

**Grammar Rules:**

1. **S → null | SS | aTa**
   - Start with S, where S can be replaced by nothing (null), two consecutive S's (SS), or a followed by T and another a (aTa).

2. **T → aUa**
   - The non-terminal T can be further expanded into a followed by U and another a (aUa).

3. **U → aUa | b**
   - U can be expanded into a followed by U and another a (aUa) or simply b.

**Example Derivation:**

We'll build a string using the production rules:

1. Start: **S → SS**
2. Apply S → SS: **S → SSS**
3. Apply S → aTa: **S → aTaSS**
4. Substitute aTa: **S → aTaaTaaTa**
5. Make substitutions:
   - **T → aUa**
   - **U → b**

After these substitutions, you arrive at the string:
- **aaUaaaaUaaaaUaa**

Finally, using the last rule:
- U's are replaced to form: **aabaaaabaaabaa**

The result is an example of a string that adheres to the grammar defined for (a^n b^a)^*, demonstrating the recursive structure and balance of a's and b's in the sequence.

**Conclusion:**

Through this example, we have constructed a string that matches the pattern specified by the grammar for (a^n b^a)^*. This illustrates how using a series of production rules can generate specific forms of strings in formal language theory.
Transcribed Image Text:**Title: Understanding Grammar for (a^n b^a)^*, Where n ≥ 2** **Introduction:** In formal language theory, we often explore grammars that generate particular patterns of strings. One such pattern is (a^n b^a)^*, where n is greater than or equal to 2. Let's explore the rules and an example of how such a grammar can be constructed. **Grammar Rules:** 1. **S → null | SS | aTa** - Start with S, where S can be replaced by nothing (null), two consecutive S's (SS), or a followed by T and another a (aTa). 2. **T → aUa** - The non-terminal T can be further expanded into a followed by U and another a (aUa). 3. **U → aUa | b** - U can be expanded into a followed by U and another a (aUa) or simply b. **Example Derivation:** We'll build a string using the production rules: 1. Start: **S → SS** 2. Apply S → SS: **S → SSS** 3. Apply S → aTa: **S → aTaSS** 4. Substitute aTa: **S → aTaaTaaTa** 5. Make substitutions: - **T → aUa** - **U → b** After these substitutions, you arrive at the string: - **aaUaaaaUaaaaUaa** Finally, using the last rule: - U's are replaced to form: **aabaaaabaaabaa** The result is an example of a string that adheres to the grammar defined for (a^n b^a)^*, demonstrating the recursive structure and balance of a's and b's in the sequence. **Conclusion:** Through this example, we have constructed a string that matches the pattern specified by the grammar for (a^n b^a)^*. This illustrates how using a series of production rules can generate specific forms of strings in formal language theory.
**Title: Generating a CFG for a Given Expression**

**Objective:**
Learn to generate a Context-Free Grammar (CFG) for a specified expression.

**Expression:**

a* bⁿ aᵐ bᵐ cⁿ 

*Where n > 0 and m ≥ 0.*

**Instructions:**
Generate a CFG that describes the expression where:
- \(a^*\) denotes zero or more occurrences of 'a'.
- \(b^n\) and \(c^n\) represent sequences where the number of 'b's and 'c's are equal and greater than zero.
- \(a^m b^m\) indicates sequences of 'a's and 'b's where the number of 'a's equals the number of 'b's and can be zero or more.

**Expectations:**
Create rules that capture the structure of the expression using CFG notation, ensuring to follow the conditions specified for \(n\) and \(m\).
Transcribed Image Text:**Title: Generating a CFG for a Given Expression** **Objective:** Learn to generate a Context-Free Grammar (CFG) for a specified expression. **Expression:** a* bⁿ aᵐ bᵐ cⁿ *Where n > 0 and m ≥ 0.* **Instructions:** Generate a CFG that describes the expression where: - \(a^*\) denotes zero or more occurrences of 'a'. - \(b^n\) and \(c^n\) represent sequences where the number of 'b's and 'c's are equal and greater than zero. - \(a^m b^m\) indicates sequences of 'a's and 'b's where the number of 'a's equals the number of 'b's and can be zero or more. **Expectations:** Create rules that capture the structure of the expression using CFG notation, ensuring to follow the conditions specified for \(n\) and \(m\).
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