SEMMA and CRISP-DM: Data Mining Methodologies

Data mining is the process of examining large sets of data for previously unsuspected patterns which can give us useful information. Data mining has a great variety of applications: it can be used to try to predict future events (such as stock prices or football scores), cluster populations into groups of people having similar characteristics, or estimate the likelihood of certain health conditions being present given other known variables.

Cross Industry Standard Process for Data Mining (CRISP-DM) is a 6-phase model of the entire data mining process, from start to finish, that is broadly applicable across industries for a wide array of data mining projects. To see a visual representation of this model, visit

CRISP-DM is not the only standard process for data mining. SEMMA, from SAS Institute, is an alternative methodology:
Sample – the subset of data should be large enough to be a representative sample but not too large of a dataset to process easily
Explore – look for patterns in the data
Modify – create and transform variables, or eliminate unnecessary ones
Model – select and apply a model that best fits your situation and data
Assess – determine whether or not your results are useful and reliable. Test your results against known data or another sample

According to the SAS website: “SEMMA is not a data mining methodology but rather a logical organisation of the functional tool set of SAS Enterprise Miner for carrying out the core tasks of data mining. Enterprise Miner can be used as part of any iterative data mining methodology adopted by the client. Naturally steps such as formulating a well defined business or research problem and assembling quality representative data sources are critical to the overall success of any data mining project. SEMMA is focused on the model development aspects of data mining.”

This is a good summary of some of the differences between CRISP-DM and SEMMA. Firstly, SEMMA was developed with a specific data mining software package in mind (Enterprise Miner), rather than designed to be applicable with a broader range of data mining tools and the general business environment. Since it is focused on SAS Enterprise Miner software and on model development specifically, it places less emphasis on the initial planning phases covered in CRISP-DM (Business Understanding and Data Understanding phases) and omits entirely the Deployment phase.

That said, there are some similarities as well. The Sample and Explore stages of SEMMA roughly correspond with the Data Understanding phase of CRISP-DM; Modify translates to the Data Preparation phase; Model is obviously the Modeling phase, and Assess parallels the Evaluation phase of CRISP-DM. Additionally, both models are intended to be somewhat cyclical rather than linear in nature. The SEMMA model recommends returning to the Explore stage in response to new information that comes to light in later stages which may necessitate changes to the data. The CRISP-DM model also emphasizes data mining as a non-linear, adaptive process.