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Factors Affecting Website Reconstruction from the Web Infrastructure. Frank McCown, Norou Diawara, and Michael L. Nelson Old Dominion University Computer Science Department Norfolk, Virginia, USA JCDL 2007 Vancouver, BC June 20, 2007. Outline. Web-repository crawling with Warrick

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Factors affecting website reconstruction from the web infrastructure

Factors Affecting Website Reconstruction from the Web Infrastructure

Frank McCown, Norou Diawara, and Michael L. Nelson

Old Dominion UniversityComputer Science DepartmentNorfolk, Virginia, USAJCDL 2007

Vancouver, BCJune 20, 2007


Outline

Outline

  • Web-repository crawling with Warrick

  • How successful is a reconstruction?

  • Reconstruction experiment

  • Significant findings


Jcdl 2007 factors affecting reconstruction from the wi

Black hat: http://img.webpronews.com/securitypronews/110705blackhat.jpgVirus image: http://polarboing.com/images/topics/misc/story.computer.virus_1137794805.jpg Hard drive: http://www.datarecoveryspecialist.com/images/head-crash-2.jpg


Crawling the crawlers

Crawling the Crawlers


Cached image

Cached Image


Cached pdf

Cached PDF

http://www.fda.gov/cder/about/whatwedo/testtube.pdf

canonical

MSN version Yahoo versionGoogle version


Jcdl 2007 factors affecting reconstruction from the wi

  • McCown, et al., Brass: A Queueing Manager for Warrick, IWAW 2007.

  • McCown, et al., Factors Affecting Website Reconstruction from the Web Infrastructure, ACM IEEE JCDL 2007.

  • McCown and Nelson, Evaluation of Crawling Policies for a Web-Repository Crawler, HYPERTEXT 2006.

  • McCown, et al., Lazy Preservation: Reconstructing Websites by Crawling the Crawlers, ACM WIDM 2006.

Available at http://warrick.cs.odu.edu/


Measuring the difference

Measuring the Difference

Apply Recovery Vector for each resource

(rc, rm, ra)

changed missing added

Compute Difference Vector for website


Some difference vectors

Some Difference Vectors

D = (changed, missing, added)

(0,0,0) – Perfect recovery

(1,0,0) – All resources are recovered but changed

(0,1,0) – All resources are lost

(0,0,1) – All recovered resources are at new URIs


How much change is a bad thing

How Much Change is a Bad Thing?

Lost

Recovered


How much change is a bad thing1

How Much Change is a Bad Thing?

Lost

Recovered


Assigning penalties

Assigning Penalties

Penalty Adjustment

(Pc, Pm, Pa)

Apply to each resource

Or Difference vector


Defining success

0

1

Less successful

More successful

Defining Success

success = 1 – dmEquivalent to percent of recovered resources


Reconstruction experiment

Reconstruction Experiment

  • 300 websites chosen randomly from Open Directory Project (dmoz.org)

  • Crawled and reconstructed each website every week for 14 weeks

  • Examined change rates, age, decay, growth, recoverability


Jcdl 2007 factors affecting reconstruction from the wi

Success of website recovery each week

*On average, we recovered 61% of a website on any given week.


Recovery of textual resources

Recovery of Textual Resources


Recovery by tld

Recovery by TLD


Birth and decay

Birth and Decay


Recovery of html resources

Recovery of HTML Resources


Recovery by age

Recovery by Age


Statistics for repositories

Statistics for Repositories


Which factors are significant

External backlinks

Internal backlinks

Google’s PageRank

Hops from root page

Path depth

MIME type

Query string params

Age

Resource birth rate

TLD

Website size

Size of resources

Which Factors Are Significant?


Mild correlations

Mild Correlations

  • Hops and

    • website size (0.428)

    • path depth (0.388)

  • Age and # of query params (-0.318)

  • External links and

    • PageRank (0.339)

    • Website size (0.301)

    • Hops (0.320)


Regression analysis

Regression Analysis

  • No surprises: all variables are significant, but overall model only explains about half of the observations

  • Three most significant variables: PageRank, hops and age (R-squared = 0.1496)


Conclusions

Conclusions

  • Most of the sampled websites were relatively stable

    • One third of the websites never lost a single resource

    • Half of the websites never added any new resources

  • The typical website can expect to get back 61% of its resources if it were lost today (77% textual, 42% images and 32% other)

  • How to improve recovery from WI? Improve PageRank, decrease number of hops to resources, create stable URLs


Thank you

Thank You

Sorry, Dad… You lost me in the first two minutes.

Frank McCown

fmccown@cs.odu.edu

http://www.cs.odu.edu/~fmccown/


Injecting server components into crawlable pages

Injecting Server Components into Crawlable Pages

Erasure codes

HTML pages

Recover at least m blocks


Jcdl 2007 factors affecting reconstruction from the wi

Web Server

Static files(html files, PDFs, images, style sheets, Javascript, etc.)

Web Infrastructure

Recoverable

config

Perlscript

Dynamicpage

Database

Not Recoverable


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