.. _DexModel:

DEX Model
=========

Models used in `DEXi Suite <https://dex.ijs.si/documentation/DEX_Software/DEXiSuite.html>`__
are prevalently *qualitative*. They are characterized by:

-  using qualitative (symbolic) :ref:`tree-structured <DexTree>` :ref:`attributes <DexAttribute>`, whose
   :ref:`scales <DexScale>` are discrete and typically consist of
   words rather than numbers,
-  employing :ref:`aggregation functions <DexFunction>` that are
   represented by (tables of) decision rules rather that numerical
   formulae.

Here, the word "qualitative" is used for contrast with more traditional
"quantitative" :ref:`decision models <MethDecisionModel>`, which are
characterized by:

-  using continuous numerical attributes, which typically represent the
   decision-maker's preferences, and
-  using numerical aggregation functions, such as the weighted sum.

In DEXi Suite, numerical attributes are supported to a limited extent and typically
constitute just a fraction of DEX models. :ref:`Numerical attributes <DexContinuous>`
can appear only as input attributes and are immediately mapped to some quantitative attribute
using the corresponding :ref:`discretization function <DexDiscretization>`.

Generally, a DEX model consists of:

- :ref:`attributes <DexAttribute>`, structured in a :ref:`tree <DexTree>`,
- qualitative and continuous :ref:`scales <DexScale>` associated with each attribute,
- aggregation and discretization :ref:`functions <DexFunction>` associated with aggregate attributes,
- :ref:`alternatives <DexAlternative>`.

.. toctree::
   :hidden:
   
   DEX_Attribute
   DEX_Tree
   DEX_Scale
   DEX_Function
   DEX_Alternative
   DEX_Value