Source Code: Forest Yield

YIELD.KSL Listing

/*
Forest Yield Example

This example implements a simple expert system that recommends a
species of tree seed, where to get the seed from, the normal yield
of the seed and how that yield should be varied according to a
description of the location, soil and conditions that hold where the
seed is to be planted.

Description
-----------
The problem is structured around a backward-chaining relation that
defines which attributes are needed to recommend a particular seed.
These attributes include the location of the site, its soil-type,
elevation, exposure and climate. When the program is testing for the
existance of a given set of attribute values the questions relating
to those attributes are asked automatically. After a suitable seed
has been found, the best provenance for the seed and its expected
yield, given the location, are calculated.

The top-level goal ensures that all the possible solutions are
returned.

Running The Example
-------------------
The forest yield example asks a series of questions and then reports
the recommended species of tree based on the given answers. To run the
example enter the following goal at the command line:

?- run .

Flex Technical Points
---------------------
The following flex technical points are demonstrated in this example:

1. The automatic asking of questions when an attribute is tested.

2. The use of group ordering in testing the answer to questions

3. The difference between setting values for logical and global
variables.

% The following templates aid the readability of the code

template valid_species_yield
valid ^ and ^ combination .

template species_yields
can find ^ with yields ^ and ^ .

template notes1
obtain seed for ^ from ^ .

template notes2
compute ^ for ^ .

template notes3
^ returns a variance of ^ .

template output
output ^, ^, ^ and ^ to the screen .

% The following top-level action gets as many species and yield
% combinations that conform to the answers given.

action run ;
do restart
and '~>'( start, Text )
and if Text is `` then write( 'No species in this knowledge base matches the data entered.<//b>' )
else write( Text )
end if .

action start ;
do for every valid Species and Yield combination
and obtain seed for Species from Provenance
and compute Variance for Provenance
do output Species, Provenance, Yield and Variance to the screen
end for .

% The questions are defined in the following section

question site
Which region is the site located in ? ;
choose one of site_types .

group site_types
'North Scotland',
'East Scotland',
'West Scotland' .

question soil
Which type of soil can be found at the site ? ;
choose one of soil_types .

group soil_types
'Brown earth',
'Gley',
'Peat',
'Podsol',
'Ironpan',
'Intergrade',
'Bog',
'Alluvium',
'Skeletal' .

question elevation
At which elevation zone is the site located ? ;
choose one of 'Lower',
'Upper' .

question exposure
In which range does the site exposure lie ? ;
choose one of exposure_types
because 'Low' = TOPEX < 30, and 'High' = TOPEX > 60 .

group exposure_types
'Low', 'Moderate', 'High'.

question gley
Which type of gley is it ? ;
choose one of 'Surface water gley',
'Flushed gley',
'Unflushed gley',
'Peaty gley' .

question status
What is the status of the peaty gley ? ;
choose one of 'Good',
'Poor' .

question peat
Which type of peat is it ? ;
choose one of 'Flushed peat',
'Unflushed peat',
'Basin peat',
'Hill peat' .

question bog
Which type of bog is it ? ;
choose one of 'Flushed bog',
'Unflushed bog' .

question moisture
What is the predominant climate of the site ;
choose one of 'Wet',
'Dry' .

question grass
Which grass is local to the site ? ;
choose one of 'Heather',
'Blue moor grass' .

question plough
Which method of ploughing is used ? ;
choose one of 'Complete',
'Spaced line' .

question flush
Is the flush local or not ? ;
choose one of 'Local',
'Non-local' .

% This section defines the main species and their yield class (both
% lower and upper) according to:
%
% i. Site location
% ii. Site elevation
% iii. Soil type
% iv. Soil sub-type
% v. Other miscellaneous factors

% Given the site location, the specific yield can be
% chosen from the upper yield or the lower yield.

relation valid Species and Yield combination
if can find Species with yields Yield1 and Yield2
and if the elevation is 'Lower'
then the Yield is Yield1
else the Yield is Yield2
end if .

% The species and expected yields (both upper and lower)
% are determined by the following relation

% The relation is split into three main sections:
% 1. The North of Scotland

relation can find 'Sitka spruce' with yields 15 and 12
if the site is 'North Scotland'
and the soil is 'Brown earth' .

relation can find 'Scots pine' with yields 8 and 7
if the site is 'North Scotland'
and the soil is 'Podsol'
and the moisture is 'Dry' .

relation can find 'Lodgepole pine' with yields 10 and 9
if the site is 'North Scotland'
and the soil is 'Podsol'
and the moisture is 'Wet' .

relation can find 'Scots pine' with yields 9 and 7
if the site is 'North Scotland'
and the soil is 'Ironpan'
and the moisture is 'Dry' .

relation can find 'Lodgepole pine' with yields 11 and 9
if the site is 'North Scotland'
and the soil is 'Ironpan'
and the moisture is 'Wet' .

relation can find 'Sitka spruce' with yields 18 and 12
if the site is 'North Scotland'
and the soil is 'Gley'
and the gley is 'Surface water gley' .

relation can find 'Sitka spruce' with yields 12 and 11
if the site is 'North Scotland'
and the soil is 'Gley'
and the gley is 'Flushed gley' .

relation can find 'Lodgepole pine' with yields 10 and 8
if the site is 'North Scotland'
and the soil is 'Gley'
and the gley is 'Unflushed gley' .

relation can find 'Sitka spruce' with yields 14 and 11
if the site is 'North Scotland'
and the soil is 'Peat'
and the peat is 'Flushed peat'
and the grass is 'Blue moor grass' .

relation can find 'Lodgepole pine' with yields 10 and 8
if the site is 'North Scotland'
and the soil is 'Peat'
and the peat is 'Flushed peat'
and the grass is 'Heather' .

relation can find 'Lodgepole pine' with yields 10 and 7
if the site is 'North Scotland'
and the soil is 'Peat'
and the peat is 'Unflushed peat' .

% 2. The East of Scotland

% Note the use of group ordering in testing the answer to the exposure
% question in the following clause

relation can find 'Sitka spruce' with yields 14 and 12
if the site is 'East Scotland'
and the soil is 'Brown earth'
and the exposure is at or above 'Moderate' according to exposure_types.

relation can find 'Douglas fir' with yields 14 and 12
if the site is 'East Scotland'
and the soil is 'Brown earth'
and the exposure is below 'Moderate' according to exposure_types .

relation can find 'Grand fir' with yields 16 and 14
if the site is 'East Scotland'
and the soil is 'Brown earth' .

relation can find 'Hybrid larch' with yields 10 and 8
if the site is 'East Scotland'
and the soil is 'Brown earth' .

relation can find 'Broadleaved' with yields 8 and 8
if the site is 'East Scotland'
and the soil is 'Brown earth' .

relation can find 'Sitka spruce' with yields 12 and 10
if the site is 'East Scotland'
and the soil is { 'Podsol' or 'Ironpan' or 'Intergrade' }
and the plough is 'Complete' .

relation can find 'Lodgepole pine' with yields 10 and 8
if the site is 'East Scotland'
and the soil is { 'Podsol' or 'Ironpan' or 'Intergrade' }
and the plough is not 'Complete' .

relation can find 'Sitka spruce' with yields 14 and 10
if the site is 'East Scotland'
and [ the soil is 'Gley' and
the gley is { 'Surface water gley' or 'Flushed gley' }
or
the soil is 'Peat' and
the peat is 'Flushed peat' ]
and the grass is not 'Heather' .

relation can find 'Lodgepole pine' with yields 10 and 8
if the site is 'East Scotland'
and [ the soil is 'Gley' and
the gley is { 'Surface water gley' or 'Flushed gley' }
or
the soil is 'Peat' and
the peat is 'Flushed peat' ]
and the grass is 'Heather' .

relation can find 'Sitka spruce' with yields 12 and 10
if the site is 'East Scotland'
and the soil is 'Gley'
and the gley is 'Unflushed gley'
and the grass is not 'Heather' .

relation can find 'Lodgepole pine' with yields 10 and 8
if the site is 'East Scotland'
and the soil is 'Gley'
and the gley is 'Unflushed gley'
and the grass is 'Heather' .

relation can find 'Sitka spruce' with yields 10 and 9
if the site is 'East Scotland'
and the soil is 'Peat'
and the peat is 'Unflushed peat'
and the flush is 'Local' .

relation can find 'Lodgepole pine' with yields 8 and 8
if the site is 'East Scotland'
and the soil is 'Peat'
and the peat is 'Unflushed peat'
and the flush is not 'Local' .

relation can find 'Lodgepole pine' with yields 6 and 6
if the site is 'East Scotland'
and the soil is 'Skeletal' .

relation can find 'Scots pine' with yields 6 and 6
if the site is 'East Scotland'
and the soil is 'Skeletal' .

% 4. The West of Scotland

relation can find 'Sitka spruce' with yields 16 and 14
if the site is 'West Scotland'
and the soil is 'Brown earth' .

relation can find 'Sitka spruce' with yields 14 and 12
if the site is 'West Scotland'
and the soil is { 'Podsol' or 'Ironpan' or 'Intergrade' } .

relation can find 'Sitka spruce' with yields 18 and 16
if the site is 'West Scotland'
and [ the soil is 'Gley' and
the gley is { 'Surface water gley' or 'Flushed gley' }
or
the soil is 'Peat' and
the peat is 'Basin peat'
or
the soil is 'Alluvium' ] .

relation can find 'Sitka spruce' with yields 14 and 12
if the site is 'West Scotland'
and [ the soil is 'Gley' and
the gley is 'Peaty gley' and
the status is 'Good'
or
the soil is 'Bog' and
the bog is 'Flushed bog' ] .

relation can find 'Sitka spruce' with yields 12 and 10
if the site is 'West Scotland'
and [ the soil is 'Gley' and
the gley is 'Peaty gley' and
the status is 'Poor'
or
the soil is 'Bog' and
the bog is 'Unflushed bog'
or
the soil is 'Peat' and
the peat is 'Hill peat' ]
and the moisture is 'Wet' .

relation can find 'Lodgepole pine' with yields 8 and 6
if the site is 'West Scotland'
and [ the soil is 'Gley' and
the gley is 'Peaty gley' and
the status is 'Poor'
or
the soil is 'Bog' and
the bog is 'Unflushed bog'
or
the soil is 'Peat' and
the peat is 'Hill peat' ]
and the moisture is 'Dry' .

% This section determines the provenance for a given
% species according to the conservancy and soil type.

relation obtain seed for 'Sitka spruce' from 'Queen Charlotte Island'
if the site is not 'South Scotland'
or the site is 'South Scotland'
and the ss_half is not 'Western half' .

relation obtain seed for 'Sitka spruce' from 'Washington'
if the site is 'South Scotland'
and the ss_half is 'Western half' .

relation obtain seed for 'Lodgepole pine' from 'Alaska'
if the site is 'North Scotland'
and the exposure is 'Low' .

relation obtain seed for 'Lodgepole pine' from 'Southern Inland'
if the site is 'North Scotland'
and the soil is 'Peat'
and the exposure is 'Moderate' .

relation obtain seed for 'Lodgepole pine' from 'Skeena River'
if the site is 'North Scotland'
and the soil is not 'Peat'
and the exposure is 'Moderate' .

relation obtain seed for 'Lodgepole pine' from 'South Coastal'
if the site is 'North Scotland'
and the exposure is 'High' .

% Note, the following relation must use "is" to set the value for "P" to
% the given value. This is because "P" is a "logical" variable.
% If instead of "P" we had "p", we would need to use "becomes" to assign
% the value for the variant "p" to the given value.
% Beware! If we used "p" and "is" this is interpreted as a check that the
% value of "p" is the same as the given value.

relation obtain seed for 'Lodgepole pine' from P
if the site is 'East Scotland'
and if the soil is 'Peat' and
the peat is 'Unflushed peat' and
the elevation is 'Upper'
then P is 'South Coastal'
else P is { 'Southern Inland' or
'Skeena River' }
end if .

relation obtain seed for 'Lodgepole pine' from P
if the site is 'West Scotland'
and P is { 'South Coastal' or
'Southern Inland' or
'Skeena River' or
'North Coastal' } .

% in this program the provenances for seeds other than 'Sitka spruce' or
% 'Lodgepole pine' are unspecified

relation obtain seed for Species from 'Unspecified Location...'
if the Species is not { 'Sitka spruce' or 'Lodgepole pine' } .

% The following section calculates the variance in the expected
% yield class according to both the exposure of the location and the
% provenance of the seed

relation compute TotalVariance for Provenance
if the exposure returns a variance of ExposureVariance
and Provenance returns a variance of ProvenanceVariance
and TotalVariance is ExposureVariance + ProvenanceVariance .

relation 'Low' returns a variance of 2 .

relation 'High' returns a variance of -2 .

relation 'Southern Inland' returns a variance of -1 .

relation 'Skeena River' returns a variance of -1 .

relation 'North Coastal' returns a variance of -2 .

relation Reason returns a variance of 0
if the Reason is not { 'Low' or
'High' or
'Southern Inland' or
'Skeena River' or
'North Coastal' } .

% The following actions output a recommended species of pine to the
% current output

action output Species, Provenance, Yield and Variance to the screen ;
do nl
and write( 'Recommended species: <//b>' ) and write( Species ) and write( '<//br>' )
and write( 'Provenance: <//b>' ) and write( Provenance ) and write( '<//br>' )
and write( 'Normal yield (+/-): <//b>' ) and write( Yield ) and write( '<//br>' )
and write( 'Yield revision: <//b>' ) and write( Variance ) and write( '<//br>' ) .