Homework 6 — Design and Implementation of a Simple Google
In this assignment you will develop a simple search engine called New York Search. Your program will mimic some of the features provided by Google. Please read the entire handout before starting to code the assignment.
Learning Objectives
- Practice writing recursive programs.
- Practice using std::map and std::set.
Background
When talking about Google Search Engine, what words come to your mind? Page Ranking? Inverted Indexing? Web Crawler?
When developing a search engine, the first question we want to ask is, where to start? When you type "Selena Gomez" or "Tom Brady" in the search box in Google, where does Google start? Does Google start searching from one specific website? The answer is Google does not start from one specific website, rather they maintain a list of URLs which are called Seed URLs. These Seed URLs are manually chosen which represent a diverse range of high-quality, reputable websites. Search engines usually have a component called web crawler, which crawls these URLs and then follow links from these web pages to other web pages. As the web crawler crawls these other web pages, it collects links from these other web pages to more web pages, and then follow these links to crawl more web pages. This process continues, ultimately, the goal is to discover as many web pages as possible. Once all pages are visited, the search engine will build a map, which is known as the inverted index, which maps terms (i.e., individual words) to web pages (also known as Documents). Below is an example:
| Key (Term) | Value (List of Document References) |
|---|---|
| apple | Document1, Document3, Document5 |
| banana | Document2, Document4 |
| orange | Document1, Document2 |
When a user enters a search query, the search engine consults its inverted index map to identify the documents that match the query term. These matching documents will then be ranked based on various factors, and the ranked documents will then be presented to the user. And this ranking process is the so-called Page Ranking.
Implementation
Based on the above description, you can see there are 3 steps when implementing a search engine:
- web crawling
- query searching
- page ranking
And thus, in this assignment, you should write your search engine following this same order of 3 steps. More details about each of these 3 steps are described below:
Web Crawling
The Web Crawler's goal is to build the inverted index.
Query Searching
The Query Search Component's goal is to identify the Matching Document.
Page Ranking
Once the search engine returns the matching documents, you should rank these documents and present the most relevant documents to the user. Google uses a variety of factors in its page ranking, but in this assignment, your page ranking are required to consider the following factors:
- Keyword Usage.
- Backlinks: The number and quality of links from other reputable websites are assessed.
- Freshness.
Period Before the Sentence
Regular Search vs Phrase Search
Useful String Functions
Assignment Scope
To reduce the scope of the assignment, and hence reduce the amount of work from you, we make the following rules for this search engine.
Rule 1. Case-sensitive Search Engine
Search engines are usually case-insensitive, but making the search engine case-insensitive will require some extra work and likely need to call some functions we have not learned in this course. Therefore, to simplify your tasks and reduce the amount of your work, in this assignment, the search engine you are going to implement is case-sensitive.
Rule 2. Search HTML Files Only
Search Engines like Google will search all types of files on the Internet, but in this assignment, we assume all files we search are HTML files. And we consider an HTML file contains the search query only if the search query can be found within the <body></body> section of the HTML file.
Based on Rule 1 and Rule 2: the third page showed in this image should not be included in your search results, when the search query is Tom Cruise.
Rule 3.
More rules will be added here.
Input Files
To be added.
Output File Format and Order
To be added.
Program Requirements & Submission Details
In this assignment, you are required to use std::map, and std::set, you are NOT allowed to use any data structures we have not learned so far, but feel free to use data structures we have already learned, such as std::string, std::vector, std::list. In addition, the web crawler component of your program must be recursive.
Use good coding style when you design and implement your program. Organize your program into functions: don’t put all the code in main! Be sure to read the Homework Policies as you put the finishing touches on your solution. Be sure to make up new test cases to fully debug your program and don’t forget to comment your code! Use the provided template README.txt file for notes you want the grader to read. You must do this assignment on your own, as described in the Collaboration Policy & Academic Integrity page. If you did discuss the problem or error messages, etc. with anyone, please list their names in your README.txt file.
Due Date: 10/26/2023, Thursday, 23:59pm.
Rubric
15 pts
- README.txt Completed (2 pts)
- One of name, collaborators, or hours not filled in. (-1)
- Two or more of name, collaborators, or hours not filled in. (-2)
- OVERALL CLASS DECLARATION & IMPLEMENTATION AND CODING STYLE (Good class design, split into a .h and .cpp file. Functions > 1 line are in .cpp file. Organized class implementation and reasonable comments throughout. Correct use of const/const& and of class method const. ) (6 pts)
- No credit (significantly incomplete implementation) (-6)
- Putting almost everything in the main function. It's better to create separate functions for different tasks. (-2)
- Function bodies containing more than one statement are placed in the .h file. (okay for templated classes) (-2)
- Missing include guards in the .h file. (Or does not declare them correctly) (-1)
- Functions are not well documented or are poorly commented, in either the .h or the .cpp file. (-1)
- Improper uses or omissions of const and reference. (-1)
- Overly cramped, excessive whitespace, or poor indentation. (-1)
- Poor file organization: Puts more than one class in a file (okay for very small helper classes) (-1)
- Poor variable names. (-1)
- Contains useless comments like commented-out code, terminal commands, or silly notes. (-1)
- DATA REPRESENTATION (5 pts)
- No credit (significantly incomplete implementation). (-5)
- Uses data structures which have not been covered in this class. (-5)
- Neither std::map nor std::set is used. (-5)
- RECURSION (2 pts)
- Does not use recursion in the web crawler component. (-2)