Editing Decision table (section)

== Overview ==

Each decision corresponds to a variable, relation or predicate whose possible values are listed among the condition alternatives. Each action is a procedure or operation to perform, and the entries specify whether (or in what order) the action is to be performed for the set of condition alternatives the entry corresponds to.

To make them more concise, many decision tables include in their condition alternatives a [[Don't-care term|don't care]] symbol. This can be a hyphen<ref>{{cite web |author=LI Jing |date=1 April 2015 |title=SEEM 3430 Tutorial: Decision Tables |url=http://www1.se.cuhk.edu.hk/~seem3430/Tutorial%20Notes/Decision%20Table.pdf |access-date=11 November 2017 |page=23 }}</ref><ref>{{cite web |date=6 August 2017 |title=Creating a Decision Table in Business Rules |website=Oracle Help Center |url=https://docs.oracle.com/en/cloud/paas/process-cloud/user/creating-decision-table-business-rules.html#GUID-26D3DF2A-D6D8-404F-834D-EE512E787630 |access-date=11 November 2017}}</ref><ref name="Ross">{{cite journal |last=Ross |first=Ronald G. |year=2005 |title=Decision Tables, Part 2 ~ The Route to Completeness |journal=Business Rules Journal |volume=6 |number=8 |url=https://www.brcommunity.com/articles.php?id=b243 |access-date=11 November 2017}}</ref> or blank,<ref name="Snow" /> although using a blank is discouraged as it may merely indicate that the decision table has not been finished.{{cn|date=November 2017}} One of the uses of decision tables is to reveal conditions under which certain input factors are irrelevant on the actions to be taken, allowing these input tests to be skipped and thereby streamlining decision-making procedures.{{sfn|LI Jing|2015|p=24-25}}

{|class="wikitable floatright mw-collapsible mw-collapsed"
|+ Demonstration of “don’t care” symbol
|-
|
{|class="wikitable"
! !! !!colspan="4" |Rules
|-
!rowspan="2"|Conditions
|Feeling energetic?    || {{yes}} || {{no}}  || {{yes}} || {{no}}
|-
|Is raining?             || {{yes}} || {{yes}} || {{no}} || {{no}}
|-
!rowspan="3"|Actions
|Stay inside             || {{MaybeCheck}} || {{MaybeCheck}} || ||
|-
|Go running              || || || {{MaybeCheck}} ||
|-
|Tend the garden         || || || {{MaybeCheck}} || {{MaybeCheck}}
|}
||
{|class="wikitable"
! !! !!colspan="3" |Rules
|-
!rowspan="2"|Conditions
|Feeling energetic?    || {{sdash}} || {{yes}} || {{no}}
|-
|Is raining?             || {{yes}} || {{no}} || {{no}}
|-
!rowspan="3"|Actions
|Stay inside             || {{MaybeCheck}} || ||
|-
|Go running              || || {{MaybeCheck}} ||
|-
|Tend the garden         || || {{MaybeCheck}} || {{MaybeCheck}}
|}
|-
|colspan="2" | The two tables convey identical information, but the second one uses a hyphen as a don't-care symbol for brevity.
|}

Aside from the basic four quadrant structure, decision tables vary widely in the way the condition alternatives and action entries are represented.<ref>{{cite web |last=Rogers |first=William T. |title=Decision Table Examples: Medical Insurance |website=Saint Xavier University Systems Analysis and Design |url=http://web.sxu.edu/rogers/sys/decision_tables.html |url-status=dead |archive-url=https://web.archive.org/web/20070329015839/http://web.sxu.edu/rogers/sys/decision_tables.html |archive-date=March 29, 2007}}</ref><ref>{{cite web |title=Decision tables |url=http://www.cems.uwe.ac.uk/jharney/table.html |url-status=dead |archive-url=https://web.archive.org/web/20120908065107/http://www.cems.uwe.ac.uk:80/jharney/table.html |archive-date=2012-09-08 |access-date=2010-07-07}}</ref> Some decision tables use simple true/false values to represent the alternatives to a condition (similar to if-then-else), other tables may use numbered alternatives (similar to switch-case), and some tables even use fuzzy logic or probabilistic representations for condition alternatives.<ref name="WetsEtAl1996">{{cite book |last1=Wets|first1=Geert |last2=Witlox|first2=Frank |last3=Timmermans|first3=Harry |last4=Vanthienen|first4=Jan |chapter=Locational choice modelling using fuzzy decision tables |chapter-url=http://repository.tue.nl/672953 |doi=10.1109/NAFIPS.1996.534708 |title=New frontiers in fuzzy logic and computing: 1996 biennial conference of the North American Fuzzy Information Processing Society&nbsp;– NAFIPS |pages=80–84 |publisher=IEEE |place=Berkeley, CA |year=1996 |isbn=0-7803-3225-3|s2cid=62056954 |url=https://research.tue.nl/nl/publications/cee188c9-baa7-40f5-804a-40e5f857eb13 }}</ref> In a similar way, action entries can simply represent whether an action is to be performed (check the actions to perform), or in more advanced decision tables, the sequencing of actions to perform (number the actions to perform).

A decision table is considered ''balanced''<ref name="Snow" /> or ''complete''<ref name="Ross" /> if it includes every possible combination of input variables. In other words, balanced decision tables prescribe an action in every situation where the input variables are provided.<ref name="Snow">{{cite web |last=Snow |first=Paul |date=19 July 2012 |title=Decision Tables |website=DTRules: A Java Based Decision Table Rules Engine |url=http://www.dtrules.com/newsite/?p=90 |access-date=11 November 2017}}</ref>