Sitecore: Extend profile matching over multiple visits

In Sitecore, to gain a better understanding of our visitors interests we have the ability to define Profile Keys and Cards to tag our content with. As our visitors navigate through the site, this data is used by Sitecore to build a profile of the visitor. A pre-defined Pattern Card that most resembles the visitors profile is then assigned to the visitor which can be used as the basis of selecting the content that should be displayed on a page for that visitor.

However what this doesn’t do is carry the visitors profile over multiple sessions. Each time a visitor comes back to the site within a new session, the visitors profile key values are reset back to zero.

So what’s Sitecore actually doing?

Before working out how to carry this information between visits, lets look at how a profile is actually being created.

If we look in the Profiles table within the Analytics database we can see the profile data that’s been recorded for a visitors visit.

Sitecore profile data

The Pattern Values column contains the current profile key scores for each key the visitor has a score for. e.g.

background=40;scope=50

If the visitor was to visit a page which has scope score of 5 and background score of 10 these values would be added to the visitors current key scores. e.g.

background=50;scope=55

When a pattern card is assigned, the card with the closest shape of keys is chosen. e.g. If the visitor has a high value for background and low value for scope they will be assigned a pattern card with similar proportional key values.

How do we extend this over multiple visits?

So the easiest way to carry the visit information from one visit to the next would be to simply copy the profile key values from the last session to the next. The code for this would look similar to the following:

var currentVisitIndex = Tracker.CurrentVisit.VisitorVisitIndex;
 
if (currentVisitIndex <= 1 || !Tracker.CurrentVisit.Profiles.Any())
{
    return;
}

var previousProfiles = Tracker.Visitor.GetVisit(currentVisitIndex - 1, VisitLoadOptions.All).Profiles;

foreach (var profile in previousProfiles)
{
    var currentProfile = Tracker.CurrentVisit.GetOrCreateProfile(profile.ProfileName);

    currentProfile.BeginEdit();

    foreach (var ProfileKey in profile.Values)
    {
        currentProfile.Score(ProfileKey.Key, ProfileKey.Value);
    }
    currentProfile.UpdatePattern();

    currentProfile.EndEdit();
}

Now the visitors profile is how it was when they left and crucially we can use this data to personalize the sites homepage for the visitor.

So why shouldn’t we do this?

As simple as this is, it comes with one potentially massive downside. If we go back to the way the profile values are built up they key values are essentially just being accumulated. Each time the visitor visits an item with a background score of 10, the visitors background profile key score in increased by 10.

Our visitors are humans going through different stages of there life, with constantly changing jobs and interests. There’s nothing to ever reduce a profile keys score other than the fact everything is normally zeroed on each visit. By copying the data from the last visit on the start of the next this would never happen and the profile key’s will continue to count up forever. The key value obtained from an item viewed 2 months ago would counted as just as important as the value from another key viewed on an item today.

So if you were running a travel site and a visitor looked at summer holidays for 3 weeks they will have a profile highly weighted towards summer holidays. If they then started to look at winter holidays we wouldn’t want them to have to look at winter holidays for 3 weeks just to have an even likeness of summer and winter.

Overcoming this issue isn’t so simple and largely depends on your business needs. If your visitors interests could change each week then you need something that will degrade the old visit data values quickly. Whereas if your trying to differentiate between people that are in a 2 week vs 6 month buying pattern, you need to retain that data a lot longer.

Some things we can do when copying the data from the visitors previous profile though could include:

  • Halving the profile scores, or reducing by a different factor. This would reduce the importance of values obtained on previous visits. So if a visitor received a 10 on the first visit, it would be worth 5 on the second, 2.5 on the third etc
  • Look at the date of the last visit. Is it to old to be relevant still or can we use the age to determine what factor we should reduce the scores by
  • Look at a combination of multiple last visits to establish what the recent scores were

All these ideas though need to be used on conjunction with what your trying to profile. If it’s age then you know people are going to get older. If it’s an interest that will change frequently then you know the data needs to degrade quickly, but if it’s male/female then that doesn’t necesserally need to degrade at all.

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