a method for measuring co-authorship relationships in mediawiki

A Method for MeasuringCo-authorship

Relationships in MediaWiki

Libby Veng-Sam TangRobert P. Biuk-Aghai

Simon Fong

Business Intelligence GroupDepartment of Computer and Information Science

Faculty of Science and TechnologyUniversity of Macau

9 September 2008 WikiSym 2008 2

Overview

Co-authoring

Calculation of degree of co-authorship

Implementation in MediaWiki

Application: Expert finder

Conclusions


Co-authoring in Wikipedia: A Myth?

Source: Wulffmorgenthaler, 8 Nov 2007, www.wulffmorgenthaler.com


Co-authoring: Why? Why co-author?

Improved article quality Pooling areas of expertise Sharing valuable ideas Sharing work Learning from others Etc.[Hart 2000]


Co-authoring: Explicit vs. Implicit Traditional mode of co-authoring: explicit

Authors explicitly agree to collaborate Authors explicitly coordinate work Authors aware of each other’s involvement Authors explicitly named


Co-authoring: Explicit vs. Implicit Wiki mode of co-authoring: implicit

Authors initiate or join writing without others’ agreement Authors take up work where interest or need perceived Authors not fully aware of other’s involvement Authors not explicitly named


Problem

Difficult to know: Who are my co-authors? What is the relative importance of my different

co-authors?


Wiki Statistics

Revisions, registered authors, pairs of authors, pages over time

550,812

5,401

301,876

57,441

0

50000

100000150000

200000

250000

300000

350000

400000450000

500000

550000

1 26 51 76 101 126 151 176 201 226 251 276 301

Weeks

Nu

mb

er

RevisionTotal RegAuthor Pair PageTotal

Source data: Wikipedia, Simple English edition, Sep. 2001-Nov. 2007

Average number of co-authors: 56


Wiki Articles Main entities:

Article (page) Revision Author

v.1v.2

v.3v.nRevisions

Article AuthorRevision11 M M


Assumptions

1. Anonymous authors and their contributions are not considered

2. Authors who have made only minor edits to a page are not considered for that page

3. All remaining authors of a page are implicitlyco-authors of that page

4. The strength of the co-authoring relationship is proportional to the number of edits made, and the length of the common co-authoring period

5. Minor edits have a lower weight than non-minor edits


Calculation Method

1. Obtain the set of all pages edited by author a2. Eliminate the pages from the set of all pages for

which author a has only made minor edits3. For each remaining page, obtain the set of other

authors4. For each set of other authors, eliminate those

authors who have only made minor edits5. For each page’s set of other authors, calculate a

page degree6. Calculate the co-authorship degree from all page

degrees


Co-Authorship Degree Calculation Co-authorship degree d for authors a and b:

where: p(a, b)i : degree of co-authorship of a and b on page i t : total number of jointly authored pages of a and b,

{t: 1 ≤ t < ∞} s : scaling constant

Range of d: (0, ∞) d is not symmetric, i.e. usually d (a, b) ≠ d (b, a)

t

iibapsbad

1

),( ),(


Page Degree Calculation:Number of ContributionsEqual number of

contributionsVastly different number of

contributions

Revisions

a

b

Authors Revisions

a

b

Authors


Page Degree Calculation:Minor vs. Non-Minor

ContributionsEqual number of minor and

non-minor contributionsAll non-minor vs. mostly

minor contributions

Revisions

a

b

Authors Revisions

a

b

Authors

Non-minor Minor


Page Degree Calculation:Co-Authoring Period

Large overlap of co-authoring period

No overlap of co-authoring period, large gap

Revisions

a

b

Authors Revisions

a

b

Authors

time time


Page Degree Calculation Page degree p for authors a and b on page i:

where: ni : number of all non-minor edits of page i

nia and nib : numbers of non-minor edits of page i by authors a and b, respectively

mi : number of all minor edits of page i

mia and mib : numbers of minor edits of page i by authors a and b, respectively

k : minor edit constant, {k: 0 ≤ k ≤ 1}

ia

ibia

i

ibia

i

ibiai L

LL

m

mmk

n

nnbap

)

),min(),min((),(

Handle different number of contributions

Handle minor contributions

Handle overlap of authoring periods


Page Degree Calculation Lia and Lib : editing periods of authors a and b on page i,

respectively (in days)

Range of p: (0, 1]

LaLb

c

Case 5a

LbLa

c

Case 5b

Case 1Lb

La c

Case 2

LaLb

c

Case 3

LaLb

c

Case 4

LaLb

c


Boundary Upper bound of page degree p:

if nia = nib ,nia + nib = n ,mia = mib ,mia + mib = m ,Lia = Lib

2

11)

2

1

2

1(),(

kkbap i


Boundary Upper bound of co-authorship degree d:

if all values of p at upper bound

2

)1(

2

1 ),(

1

ktsksbad

t

i


Complexity Main operations of algorithm:

1 FOR each co-author in the author’s co-author list2 FOR each co-authored page authored by the given

author and co-author3 CALCULATE the page degree for the current

page ofthe given author and co-author

4 ACCUMULATE the page degree as co-author degreeEND FOR5 STORE the co-author degree of the co-author

END FORSimple operations,

negligibleApproximates to

constantMain factors

affecting performance


Complexity Given a constant processing time for calculating

page degree:

where: PT( ) : a function which returns the processing time a : the given author bi : co-author i of the given author a

d( ) : degree of co-authorship of a and bi

p( )j : page degree of page j co-authored by a and bi

C : constant processing time for computing page degree

n

i

n

i

mi

j

n

i

mi

jjii CbapPTbadPT

1 1 11 1

)),(()),((


Complexity n : number of co-authors of a mi : number of co-authored pages by a and bi, it is

variant for each co-author pair I

Assume n = mi :quadratic complexity, i.e. O(n2)


Implementation in MediaWiki Database: Wikipedia Simple English

Dump date: 16 Nov 2007 Revisions: 550,812 Pages: 57,441 Useful articles: ~20,000 Registered authors: 5,401

Category of revision Rev./Page %

All 9.8362 100.0

Non-minor edit 5.3583 54.5

Minor edit 4.4782 45.5

Submitted by registered author 8.1414 82.8

Submitted by anonymous author 1.6951 17.2



Growth of number of revisions: total (top) increment (right)

0

100000

200000

300000

400000

500000

118 168 218 268 318

Revision - All

Revision - Reg. Author

Revision - Anonymous

Week No.

0

2000

4000

6000

8000

10000

118 168 218 268 318

Revision - All

Revision - Reg. Author

Revision - Anonymous

Poly. (Revision - All)

Poly. (Revision - Reg. Author)

Poly. (Revision - Anonymous)

Week No.


Implementation in MediaWiki Implementation as MediaWiki extension, category

‘Special Page’



1. Author name

2. Sort order

3. Degree ofco-authorship

4. Visualization ofdegree

5. Link to co-author’sco-authors


Performance Online calculation Server:

Windows PC, 3 GHz Intel Pentium 4 CPU, 2 GB RAM Primary performance target: 2 sec. Secondary performance target: 10 sec. Actual performance:

Algorithm’s quadratic complexity online calculation for small/mid-size databases offline calculation for large databases

t ≤ 2 sec. 2 sec. < t ≤ 10 sec. t > 10 sec.

92% 7% 1%


Application: Expert Finder Assumptions:

Authors are experts on an article’s subject Co-authors are potential co-experts

Approach: Pick an article as starting point Expand to articles from category(ies) of the article Find main authors of selected articles Expand to close co-authors Filter resulting list


Application: Expert Finder

Approach: 1. Pick starting article


2. Expand to category articles


Approach:


3. Get article authors


Approach:


4. Restrict to main authors


Approach:


5. Get close co-authors


Approach:


6. Merge with close co-authors


Approach:


Application: Expert FinderApproach: 7. Filter author list: expert list


Expert Finder: Implementation


Conclusions Contribution:

New method for determining degree of co-authorship Applications:

Not limited to MediaWiki – applicable to all collaborative writing systems with revision history

Visualization systems for wikis Basis for further analytical applications

Limitations: Actual level of expertise? Wikipedia: much content

requires little real “expertise” better for corporate wikis Ongoing work:

Reconstruct edit history within revisions to determine significance of contribution (instead of minor/non-minor)

a method for measuring co-authorship relationships in mediawiki

Technology

b authors revisions

page degree of pagejco

computing page degree

implicit authors

explicit authors

minor contributions

b case

remaining page