Are we following the expected process?
With conformance checking, people aim to compare the behavior that occurs in reality with the one that is captured in the process model.
What is conformance checking?

Conformance checking is a discipline that compares events in the event log with the activities in the process model. The process model may have been constructed by hand or may have been discovered. Using conformance checking algorithms, people may know if the real-life process is running as expected or modeled. In case it is not, the process owner can have timely actions either to improve the process model or to correct the deviations in reality.

Use case
There are three main use cases:
  • Compliance checking (for auditing, fraud detection, etc.):
    • Audits are performed to ascertain the validity and reliability of information about organizations and their associated processes.
    • The audits help in checking whether business processes are executed within certain boundaries set by managers, governments, and other stakeholders.
  • Evaluating process discovery results/algorithms:
    • Comparing discovered process models with the data used to learn the model or with unseen test data.
    • Evaluating a model or an algorithm (see k-fold cross-validation).
  • Conformance to specification (software, services, etc.)
Conformance checking algorithm
Token Replay
Token-replay is a heuristic technique, which uses four counters (produced tokens, consumed tokens, missing tokens, and remaining tokens) to compute the fitness of an observation trace based on a given process model. Although the approach is easy to understand and can be implemented efficiently, since token-replay takes a local decision, it may lead to misleading results.
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Alignments
Alignments is a technique, which performs an exhaustive search to find out the optimal alignment between the observed trace and the process model. Hence, it is guaranteed to return the closest model run in comparison to the trace.
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"A nice analogy that tells the difference between token-replay and alignments is searching for a particular place (e.g., a restaurant) in a city: in token-replay, you decide the direction to take just by looking at what you see. With alignments, you take your mobile phone and look at Google Maps, which will tell the optimal route (but pays the price of connecting to a GPS, download the city map, etc. …)"