SEO, content quality and mathematical determination with WDF*IDF

Pubcon New Orleans

I was touring the US and British SEO conferences in the past 3 weeks and I am amazed, that the basic text quality calculation (which was mentioned on nearly every German conference) finds little to no attention by the international crowd.

So, let me summarized the idea of WDF*IDF in English for you. It was brought up by the German SEO Karl Kratz, who should be mentioned here for digging into the mathematical basics on conferences in the past months. He does not get tired to mention that it is an “old” formular he dug up in a book from the 70’s and is mentioned again in the early books about search engine technologies (see Wikipedia).

The executive summary for the hard working SEO is: There is a formula to automatically determine the quality of a text. This formula uses basic “term counting” and compares it to values derived from the amount of “document counting”. It sets these numbers in relation and finds a “corpse” of documents that really cover a topic in depth.

And let us all say: “NO, it is not keyword density!

While all SEOs who talk about how important quality of a text became and who know that Google does compute the results automatically (with SPAM fighters controlling the results), should get an AHA moment right now.

It is also worth mentioning, that the values deriving out of the formula is just ONE signal like links, link neighborhood, clean HTML code, headlines, etc., yet it is a good working part of your SEO work today.

Here is an example, how we went up with our WordPress plugin “exopin” that we offer for “blogging for money” – so people who want to sell their blog posts directly from their WordPress blog.

wdf idf result blogging for money

The snapshot shows us ranking on position #7 for the key term and we have not been building links to that page. The only place it is linked from is the WordPress.org directory, which is a strong, clean link. I admit, it is a strong one, but it also is the only link that was necessary to reach that position.

So: How does that WDF*IDF basically work? If you want to use it, you will need more than my basic explanation, but it should get you started:

The formula calculates the RELATED terms to a search term you want to rank for. It gives you an overview of the most important related terms, that appear on sites that are ranking highly on Google related to the search key you entered. The visualization looks like this:

wdf idf term weight

and tools like OnPage.org have implemented that calculation in their set of SEO tools to assist you in finding the related terms and most of all weighs these terms, too.

The analysis relates and weighs the terms of the top results and gives you a set of terms you should use in the article you want to rank. It is pretty clear by the tests we have done, that this helps a lot, if you have all other factors covered and gives you a rough idea of your text quality. You see in our blogging for money example, that it works just fine, if you got the other factors under control!

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