Software tool for detecting plagiarism in computer source code

• US 20080270991A1
• Filed: 07/07/2008
• Published: 10/30/2008
• Est. Priority Date: 11/25/2003
• Status: Active Grant

• Current Assignee: SAFE IP LLC (Pueblo Nuevo LLC)
• Original Assignee: Robert M. Zeidman
• Inventors: Zeidman, Robert M.
• Granted Patent: US 8,261,237 B2
• Time in Patent Office: Days
• US Class Current: 717/126
• CPC Class Codes: G06F 21/16 Program or content traceability, e.g. by watermarking
• CPC Class Codes: G06F 40/194 Calculation of difference between files
• CPC Class Codes: G06F 8/71 Version control security arrangements therefor G06F21/57; Configuration management
• CPC Class Codes: G06Q 50/18 Legal services

Abstract

A method and system for detecting plagiarism of software source code. In one embodiment, a first set of arrays and a second set of arrays are created for a first program source code file and a second program source code file respectively. Each pair of arrays in the first and second sets has entries corresponding to program elements of a distinct program element type such as functional program code, program comments, or program code identifiers. Next, each pair of arrays from the first and second sets is compared to find similar entries, and an intermediate match score is calculated for each pair of arrays based on the similar entries. Further, the resulting intermediate match scores are combined to produce a combined match score, which is then used to provide an indication of copying with respect to the first program source code file and the second program source code file.

Claims

1. A computer-implemented method comprising:

creating a first array based on a first program source code file including a plurality of program elements, the first array having entries corresponding to lines of functional program code from the first program source code file;

creating a second array based on a second program source code file including a plurality of program elements, the second array having entries corresponding to lines of functional program code from the second program source code file;

comparing the first array with the second array to find a longest sequence of similar entries;

calculating a match score based on a number of lines in the longest sequence; and

providing an indication of copying with respect to the first program source code file and the second program source code file, wherein the indication of copying is defined by the match score.

2. The method of claim 1 wherein comparing the first array with the second array comprises finding entries of the first array with first words that are similar to first words of entries of the second array, wherein an order of found entries in the first array corresponds to an order of entries with the similar first words in the second array.

3. The method of claim 1 wherein providing an indication of copying with respect to the first program source code file and the second program source file comprises:

presenting a report identifying the first program source file and the second program source code file, and the match score calculated based on the comparison; and

allowing a user to select the match score to view the similar entries.

4. The method of claim 1 wherein the first and second arrays are created based on program dependant information.

5. A computer-implemented method comprising:

creating a first set of arrays based on a first program source code file including a plurality of program elements, each of the arrays of the first set of arrays having entries corresponding to program elements of a distinct program element type represented by at least one of functional program code, program comments, and program code identifiers;

creating a second set of arrays for a second program source code file including a plurality of program elements, the second set of arrays having entries of one or more program element types corresponding to program element types of entries in the first set of arrays;

comparing the arrays of the first set with the arrays of the second set to find similar entries;

calculating a plurality of intermediate match scores based on the similar entries, each of the plurality of intermediate match scores being calculated for a pair of corresponding arrays from the first and second sets;

combining the plurality of intermediate match scores to produce a combined match score; and

providing an indication of copying with respect to the first program source code file and the second program source code file, wherein the indication of copying is defined by the combined match score.

6. The method of claim 5 wherein the plurality of intermediate match scores are combined using corresponding weights.

7. The method of claim 5 wherein providing an indication of copying with respect to the first program source code file and the second program source file comprises:

presenting a report identifying the first program source file and the second program source code file, and the match score calculated based on the comparison; and

allowing a user to select the match score to view the similar entries.

8. The method of claim 5 wherein the first and second sets of arrays are created based on program dependant information.

9. The method of claim 5 wherein:

an array from the first set and an array from the second set have a program element type represented by functional program code; and

calculating an intermediate matching score comprises finding a number of matching lines of functional program code in the array from the first set and the array from the second set.

10. The method of claim 9 wherein entries in the array from the first set and the array from the second set exclude lines consisting entirely of programming keywords.

11. The method of claim 5 wherein:

an array from the first set and an array from the second set have a program element type represented by program comments; and

calculating an intermediate matching score comprises finding a number of matching comment lines in the array from the first set and the array from the second set.

12. The method of claim 5 wherein:

an array from the first set and an array from the second set have a program element type represented by program code identifiers;

the similar entries comprises similar program code identifiers; and

calculating an intermediate matching score comprises computing a number of the similar program code identifiers.

13. The method of claim 12 wherein calculating an intermediate matching score further comprises combining a number of alphabetical characters in the similar program code identifiers and a fraction of a number of numerical characters in the similar program code identifiers.

14. The method of claim 5 wherein:

an array from the first set and an array from the second set have a program element type represented by functional program code; and

comparing the array from the first set with the array from the second set comprises finding a longest sequence of similar entries; and

calculating an intermediate match score comprises finding a number of lines contained in the longest sequence.

15. The method of claim 14 wherein comparing the array from the first set with the array from the second set comprises finding entries in the array from the first set that contain similar first words as the array from the second set, wherein an order of found entries in the array from the first set corresponds to an order of entries with the similar first words in the array from the second set.

16. A computer-readable storage medium storing executable instructions to cause a computer system to perform a method comprising:

creating a first set of arrays based on a first program source code file including a plurality of program elements, each of the arrays of the first set of arrays having entries corresponding to program elements of a distinct program element type represented by at least one of functional program code, program comments, and program code identifiers;

creating a second set of arrays for a second program source code file including a plurality of program elements, the second set of arrays having entries of one or more program element types corresponding to program element types of entries in the first set of arrays;

comparing the arrays of the first set with the arrays of the second set to find similar entries;

calculating a plurality of intermediate match scores based on the similar entries, each of the plurality of intermediate match scores being calculated for a pair of corresponding arrays from the first and second sets;

combining the plurality of intermediate match scores to produce a combined match score; and

providing an indication of copying with respect to the first program source code file and the second program source code file, wherein the indication of copying is defined by the combined match score.

17. The computer-readable storage medium of claim 16 wherein the plurality of intermediate match scores are combined using corresponding weights.

18. The computer-readable storage medium of claim 16 wherein:

an array from the first set and an array from the second set have a program element type represented by functional program code or program comments; and

calculating an intermediate matching score comprises finding a number of matching lines of functional program code or comment lines in the array from the first set and the array from the second set.

19. The computer-readable storage medium of claim 16 wherein:

an array from the first set and an array from the second set have a program element type represented by program code identifiers;

the similar entries comprises similar program code identifiers; and

calculating an intermediate matching score comprises computing a number of the similar program code identifiers.

20. The computer-readable storage medium of claim 16 wherein:

an array from the first set and an array from the second set have a program element type represented by functional program code; and

comparing the array from the first set with the array from the second set comprises finding a longest sequence of similar entries; and

calculating an intermediate match score comprises finding a number of lines contained in the longest sequence.