What is an Event Log?
To begin with, these are the most frequently asked questions:
Why do we need an Event Log? To be able to apply process mining techniques.
What is an Event Log? The simplest example would be a CSV file that contains at least these three columns: Case ID, Activity and Timestamp.
Tip
Never forget these columns by remembering CAT.
How can I identify these columns in a CSV file? The easiest way to evaluate your CSV file is to first sort your data according to the column you think is your Case ID and then by Timestamp, as shown in the screenshot below.
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The result would be the following:
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This CSV file is a quality Event Log because it follows the Event Log principles:
An Event Log can be seen as a collection of cases. For instance in the screenshot above our collection would be FN338, GH2230, LH2286 and LH2306.
A case can be seen as a clear sequence of activities. For example, for case FN338 we have a clear sequence of activities: Check-in, Boarding, Takeoff, Landing and Baggage claim.
Let’s look at some bad examples that don’t follow these principles.
Example 1: One Activity per Case.
For instance, we have the following event log shown in the screenshot below.
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Let’s apply the same trick. First, we sort according to the column we think is our Case ID and then by Timestamp.
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The result after sorting will be the following table:
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What we can immediately see here is that we are violating the second principle of an Event Log
A case can be seen as a clear sequence of activities.
because we don’t have a sequence of activities since there is only one activity per case.
Example 2: The same timestamp for all activities.
We have the Event Log shown in the screenshot below.
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After we apply the same trick (sort according to the column we think is our Case ID and then Timestamp) we have the result shown below.
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What we can immediately see here is that we are again violating the second principle of an Event Log
A case can be seen as a clear sequence of activities.
because we don’t have a clear sequence of activities since all the activities happen at the same time.
Example 3: Hundreds of activities for one case.
This is also wrong because it violates the first principle
An Event Log can be seen as a collection of cases.
because in this example, we have only one case.