Since Det 3.001 you can change the default Det behavior if required. The logic setup window opens after pressing the button "Logic". The you can change the following options:

Behavior after choosing the proposition

When one of the two propositions is chosen, the simpliest way is to accept the list, associated with chosen proposition. The other way (default) is to remove the conditions, asscociated with the rejected proposition, from the current list (after start, this list contains all conclusions defined in the database).

[X] Unconditionally accept list of concusions, pointed by chosen proposition, as current list
Accept the list, associated with chosen proposition. If this box is checked, all other boxes has no effect. This algorhythm was used in Det 1.0-2.0 . Check this box to reach the simpliest and the most predictive behavior if you are only using multiple trees, but not rules nor tables.

[X] Discard all conclusions that are pointed by rejected propositon
This box, checked by default, activates the discarding mechanism. Description tables work well only if this method is used. However, for certain keys the method is more active if the following exceptions are also taken into account:

[X] Don't discard conclusions included in the lists of both propositons
Normally, the same conclusion don't appear in both lists. However you can do this manually by writing ungrouped rule, for example:
?[A,B,C] 'First proposition ' [A+B] 'Alternative proposition' [A+C];
In such case, without this exception this rule always rejects the conclusion A independently from the answer. If the box is checked, this rule does not change the status of A conclusion.

[X] Always add conclusions, present in proposition list, but absent in current list
This mode allows to accept some new conclusions after one final concluson is reaches, starting new determining process. For example, in guide on lichens, you can find the following rule:
?[Ramalina_sp] 'It can be one of the Ramalina species. Press "Yes" to determine more exactly. ' [Ramalina_fraxinea+Ramalina_fastigiata+Ramalina_farinacea] ' ' [ALL];

In this case, after reaching the conclusion Ramalina_sp, the three new conclusions are accepted to define Ramalina species more exactly, possibly using the rules from other included keys.

[X] If current conclusion list becomes empty, accept the list of selected proposition
The situation might arise when all possible conclusions are rejected and the current list becomes empty. If the box is checked, Det then accepts the list associated with selected proposition as current. Otherwise, there is no possible to continue and the determining process restarts from beginning.

[X] When switching between sources, accept list of conclusions of the chosen rule in new source
The exception is useful when switching between two dichotomic keys.

> [X] Dont use the exception above when switching into ungrouped rule
> For ungrouped rules, the exception only decreases performance/

[X] Ignore the exsistence of not - included possible conclusions
Orders to ignore ("don't see") the conclusions, not described within the current key. Without this exception, if one of the keys is incomplete (for example, older), it rules quite often can't be launched because the the absence of these undescribed conclusion in they entry list.

> [X] Make this exception only if the source covers at least half of possible conclusions
> However, some keys can be really short, being specialised for a certain subset of possible conclusions, as the key on Cladonia and Lobaria in the Lichenes.key example. This box cancels the effect of upper box for a sources that contain less than half of all possible conclusions defined in the database.

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