In the original paper on this titled "Detecting Online Commercial Intention", they defined online commercial intention (OCI) as follows:
OCI is a "function from a query or a web page to a binary value: Commercial or Non-Commercial. More specifically, if the general purpose of users submitting the query or visiting the web page is to commit a commercial activity, such as purchase, auction, selling, or paid service, the query can be treated as Commercial. Otherwise, the query/web page is considered as non-commercial."
They used a labeling process to generate a training set of web page characteristics and then a learning model to build a OCI detector. Using this they could classify a page as commercial or non-commercial.
Then they looked at the first result page a search engine returned for a query and determined the OCI of the pages returned. Using a weighting process an OCI probability is assigned to the search query.
That is a real simplified explanation. Some of the things learned were interesting.
1. Even for a high OCI probability, there is a "Commercial Activity Phase" (CAP) during which the searcher to collecting information prior to a commercial act. They are doing research on ways to detect this so that what is presented to the searcher is more relevant to where they are in the process.
2. The more a particular search term is used, the more likely it is to be a commercial term. They looked at a month of search queries and found 32% of queries that occurred just once had commercial intent whereas 41% of high frequency queries had commercial intent.
An OCI of 1 means all the 10 pages listed on first SERP and the landing pages they link to have commercial intent based on their classification process. However, if the number is 0.8, that does not mean that 8 had commercial intent because they weight the score based on position on SERP and the landing page linked to. Since this is a learning model, it is always changing and should get better over time.
If it is an OCI of 1, you can probably be sure that all results on first SERP are your commercial competitors and not just information sites.