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2.2. BASIC NOTIONS IN MININGMART
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Operator An operator performs a single, precisely defined task on the business data. An operator is applied by creating a step, setting its parameters,
and compiling the step. A step’s parameters define the input and output for
an operator in terms of the data on the conceptual level. There are two basic
kinds of operators: those whose output is a concept and those that add an extra
feature to their input concept. A few operators do not belong to either of these
categories. Examples for tasks that operators perform are the replacement of
missing values in the data that belongs to the input concept, or the creation of
a new view on the data from the input concept, or the selection of important
features from the input concept, etc.
A list of all operators with their technical description and details can be
found in chapter 4.
Parameter Parameters are related to steps; they define their input and output
on the conceptual level. Some parameters that many steps need are: TheInputConcept, which defines the concept whose data is processed; TheOutputConcept
or TheOutputAttribute, which define the output, ie the result of processing;
etc. For every operator, its parameters are listed in detail in chapter 4.
Concept A concept in MiningMart represents an everyday notion for which
there exists data in the database. For example, as mentioned earlier, a concept “Customer” may exist in MiningMart and refer to one or more tables in
the database that contain data about customers. Concepts have features which
define them. The MiningMart system provides a concept editor to create, edit
and delete concepts and their features. Concepts belong to the conceptual level.
Concepts are connected to ColumnSets which represent the database contents
on the relational level.
There are two types of concepts: DB and MINING. The first type are concepts whose data exists before any MiningMart step is executed. That is, these
concepts represent the input data for the case. All MINING concepts, in contrast, are not connected to any data before the execution (called compilation)
of a MiningMart step. The MiningMart compiler creates the data that belongs
to the MINING concepts and connects it to them. See also under compiler and
connection.
Subconcept link A concept is a subconcept of another concept if it has the
same list of features, but the corresponding Columnset contains only rows that
are also present in the other concept’s columnset. The link between a subconcept
and its super concept is displayed in the Concept Editor as a dashed arrow.
Projection A concept is a projection of another concept if all of its features appear in the other concept, but the other concept also has at least one additional
feature. Further, the corresponding columnset contains only rows that are also
present in the other concept’s columnset (except for the additional feature(s)).
A projection link is displayed in the Concept Editor as a dotted arrow.