Saturday, July 16, 2011

What happens to an evalid site analysis run if my website changes in the middle of the run?

An eValid user wrote:

What happens to an evalid site analysis run if my website changes in the middle of the run?

Here is the way the site analysis engine works.

It starts (at the page you specify) and makes a list of all of the links on that page and then, one by one, it attempts to visit every page on that list.

On each new page, it ADDs to the "work list" by enumerating all of the links on that page.

No page is visited a second time, and the scan stops when the "work list" is empty.

Now, if one of the pages changes during the scan, then the NEW information will be used as the basis for adding items to the "work list". If the new page has left out a link that was present at the time the scan began, then that page will not land in the "work list" and will never be visited.

So, bottom line, if the site changes there is a risk that some pages that were present at the time the scan started will not be visited, and there is a corresponding risk that some pages that were not present at the time the scan started will be visited.

Practically speaking, if you are running a scan regularly, ultimately all of the pages' actual [stable] content will be visited, so this effect may not be an issue for you. But a one-off scan may be in error.

It's best, of course, to run scans on stable sites that are not undergoing maintenance and/or upgrade and/or change.

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eValid Tech Support

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