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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 Infrastructure

  • Web-repository crawling with Warrick

  • How successful is a reconstruction?

  • Reconstruction experiment

  • Significant findings

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 http://img.webpronews.com/securitypronews/110705blackhat.jpg

Cached image
Cached Image http://img.webpronews.com/securitypronews/110705blackhat.jpg

Cached pdf
Cached PDF http://img.webpronews.com/securitypronews/110705blackhat.jpg



MSN version Yahoo version Google version

  • McCown, et al., http://img.webpronews.com/securitypronews/110705blackhat.jpgBrass: 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 http://img.webpronews.com/securitypronews/110705blackhat.jpg

Apply Recovery Vector for each resource

(rc, rm, ra)

changed missing added

Compute Difference Vector for website

Some difference vectors
Some Difference Vectors http://img.webpronews.com/securitypronews/110705blackhat.jpg

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? http://img.webpronews.com/securitypronews/110705blackhat.jpg



How much change is a bad thing1
How Much Change is a Bad Thing? http://img.webpronews.com/securitypronews/110705blackhat.jpg



Assigning penalties
Assigning Penalties http://img.webpronews.com/securitypronews/110705blackhat.jpg

Penalty Adjustment

(Pc, Pm, Pa)

Apply to each resource

Or Difference vector

Defining success

0 http://img.webpronews.com/securitypronews/110705blackhat.jpg


Less successful

More successful

Defining Success

success = 1 – dmEquivalent to percent of recovered resources

Reconstruction experiment
Reconstruction Experiment http://img.webpronews.com/securitypronews/110705blackhat.jpg

  • 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

Success of website recovery each week http://img.webpronews.com/securitypronews/110705blackhat.jpg

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

Recovery of textual resources
Recovery of Textual Resources http://img.webpronews.com/securitypronews/110705blackhat.jpg

Recovery by tld
Recovery by TLD http://img.webpronews.com/securitypronews/110705blackhat.jpg

Birth and decay
Birth and Decay http://img.webpronews.com/securitypronews/110705blackhat.jpg

Recovery of html resources
Recovery of HTML Resources http://img.webpronews.com/securitypronews/110705blackhat.jpg

Recovery by age
Recovery by Age http://img.webpronews.com/securitypronews/110705blackhat.jpg

Statistics for repositories
Statistics for Repositories http://img.webpronews.com/securitypronews/110705blackhat.jpg

Which factors are significant

External backlinks http://img.webpronews.com/securitypronews/110705blackhat.jpg

Internal backlinks

Google’s PageRank

Hops from root page

Path depth

MIME type

Query string params


Resource birth rate


Website size

Size of resources

Which Factors Are Significant?

Mild correlations
Mild Correlations http://img.webpronews.com/securitypronews/110705blackhat.jpg

  • 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 http://img.webpronews.com/securitypronews/110705blackhat.jpg

  • 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 http://img.webpronews.com/securitypronews/110705blackhat.jpg

  • 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 http://img.webpronews.com/securitypronews/110705blackhat.jpg

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

Frank McCown

[email protected]


Injecting server components into crawlable pages
Injecting Server Components into Crawlable Pages http://img.webpronews.com/securitypronews/110705blackhat.jpg

Erasure codes

HTML pages

Recover at least m blocks

Web Server http://img.webpronews.com/securitypronews/110705blackhat.jpg

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

Web Infrastructure






Not Recoverable