Data file for Tiers (Tier Two to Tier 4).

data.php

<?php

defined( 'SITE' ) || exit;

/**
 * Get Tier Two Data (Three Characters).
 *
 * Who, What, When, Where, How and Why, shortened to:
 * who, wha, whn, whe, how and why.
 *
 * Although each tier two grouping can have about ten tier
 * three groupings, some (many?) may be duplicated at the tier three
 * and tier four levels, with minor variations in wording to reflect
 * the difference between the tier two groupings.
 *
 * @return array
 */
function get_tier_two_data(){
	$arr = [
		'who' => [ 'name' => 'who' ],
		'wha' => [ 'name' => 'what' ],
		'whn' => [ 'name' => 'when' ],
		'whe' => [ 'name' => 'where' ],
		'how' => [ 'name' => 'how' ],
		'why' => [ 'name' => 'why' ],
		];
	return $arr;
}

/**
 * Get Tier Three Data (Four Characters).
 *
 * These all are currently placed under the "Where" (whr) directory.
 * Formerly, this was called the "cluster" directory, as that had best
 * defined what that was at that time. However, with the addition of
 * other higher level categories which include: who, what, when, how and
 * why, it seemed best to change this to "where" (or "whr") for consistency.
 *
 * @return array
 */
function get_tier_three_data(){
	$arr = [

		// whe (where)
		'acad' => [ 'name' => 'academic' ],
		'arts' => [ 'name' => 'arts' ],
		'trad' => [ 'name' => 'trade' ],
		'appl' => [ 'name' => 'applied' ],
		'gard' => [ 'name' => 'gardening' ],
		'care' => [ 'name' => 'care' ],
		'cafe' => [ 'name' => 'cafe' ],
		'moni' => [ 'name' => 'monitoring' ],
		'anal' => [ 'name' => 'analysis' ],
		'natu' => [ 'name' => 'nature' ],

		// nature
		'natu' => [ 'name' => 'nature' ],

		// wha
		'agri' => [ 'name' => 'agriculture' ],
		'bldg' => [ 'name' => 'building' ],
		'equi' => [ 'name' => 'equipment' ],
		'supp' => [ 'name' => 'supply' ],
		'prop' => [ 'name' => 'property' ],
		'reso' => [ 'name' => 'resource' ],
		'stru' => [ 'name' => 'structure' ],
		'info' => [ 'name' => 'information' ],
		'prod' => [ 'name' => 'product' ],
		'desn' => [ 'name' => 'design' ],

		// how
		'stnd' => [ 'name' => 'standard' ],
		'proc' => [ 'name' => 'process' ],
		'proj' => [ 'name' => 'project' ],
		'comm' => [ 'name' => 'communication' ],
		'news' => [ 'name' => 'news' ],
		'serv' => [ 'name' => 'service' ],
		'whsl' => [ 'name' => 'wholesale' ],
		'stor' => [ 'name' => 'storefront' ],

		// recycling
		'reco' => [ 'name' => 'recovery' ],

		// why
		'ethc' => [ 'name' => 'ethics' ],
		'sust' => [ 'name' => 'sustainability' ],
		'reln' => [ 'name' => 'religion' ],
		'othr' => [ 'name' => 'other' ],
	];
	return $arr;
}

/**
 * Get Tier Four Data (Five Characters).
 *
 * There are eight to ten tier three groupings. With about eight
 * tier four groupings per tier three grouping, we have:
 * 10 x 8 = 80. About sixty to eighty tier four groupings.
 *
 * @return array
 */
function get_tier_four_data(){
	$arr = [
		'centr' => [ 'name' => 'center' ],

		'chemi' => [ 'name' => 'chemistry', 'who' => 'chemist', ],
		'cogni' => [ 'name' => 'cognition', 'who' => 'psychologist', ],
		'cymat' => [ 'name' => 'cymatics', 'who' => 'cymaticist', ],
		'genet' => [ 'name' => 'genetics', 'who' => 'geneticist', ],
		'geolo' => [ 'name' => 'geology', 'who' => 'geologist', ],
		'logic' => [ 'name' => 'logic', 'who' => 'logician', ],
		'mathe' => [ 'name' => 'mathematics', 'who' => 'mathematician', ],
		'physc' => [ 'name' => 'physics', 'who' => 'physicist', ],

		'archi' => [ 'name' => 'architecture', 'who' => 'architect', ],
		'engin' => [ 'name' => 'engineering', 'who' => 'engineering', ],
		'lands' => [ 'name' => 'landscaping', 'who' => 'landscaper', ],
		'perma' => [ 'name' => 'permaculture', 'who' => 'permaculturist', ],
		'progr' => [ 'name' => 'programming', 'who' => 'programmer', ],
		'robot' => [ 'name' => 'robotics', 'who' => 'roboticist', ],

		'music' => [ 'name' => 'music', 'who' => 'musician', ],
		'paint' => [ 'name' => 'painting', 'who' => 'painter', ],
		'percn' => [ 'name' => 'percussions', 'who' => 'percussionist', ],
		'piano' => [ 'name' => 'piano', 'who' => 'pianist', ],
		'pttry' => [ 'name' => 'pottery', 'who' => 'potter', ],
		'saxop' => [ 'name' => 'saxophone', 'who' => 'saxophonist', ],
		'sclpt' => [ 'name' => 'sculpture', 'who' => 'sculptor', ],
		'violn' => [ 'name' => 'violin', 'who' => 'violinist', ],

		'bakng' => [ 'name' => 'baking', 'who' => '', ],
		'brsta' => [ 'name' => 'barista', 'who' => 'barista', ],
		'clnup' => [ 'name' => 'cleanup', 'who' => 'cleaner', ],
		'cookg' => [ 'name' => 'cooking', 'who' => 'cook', ],
		'recyl' => [ 'name' => 'recycling', 'who' => 'recycler', ],
		'servg' => [ 'name' => 'serving', 'who' => 'server', ],
		'storg' => [ 'name' => 'storage', 'who' => 'storagist', ],

		'bodie' => [ 'name' => 'baking', 'who' => 'baker', ],
		'cloth' => [ 'name' => 'clothing', 'who' => 'tailor', ],
		'hairc' => [ 'name' => 'haircare', 'who' => 'hairdresser', ],
		'ntrtn' => [ 'name' => 'nutrition', 'who' => 'nutritionist', ],
		'physo' => [ 'name' => 'physio', 'who' => 'physiotherapist', ],
		'psych' => [ 'name' => 'psyche', 'who' => 'pscyhologist', ],

		'culti' => [ 'name' => 'cultivating', 'who' => 'cultivator', ],
		'hrvtg' => [ 'name' => 'harvesting', 'who' => 'harvester', ],
		'plntg' => [ 'name' => 'planting', 'who' => 'planter', ],
		'prepg' => [ 'name' => 'preparing', 'who' => 'preparer', ],
		'procg' => [ 'name' => 'processing', 'who' => 'processer', ],
		'weedg' => [ 'name' => 'weeding', 'who' => 'weeder', ],

		'anlys' => [ 'name' => 'analysis', 'who' => 'analyst', ],
		'audio' => [ 'name' => 'audio', 'who' => 'audio-engineer', ],
		'photo' => [ 'name' => 'photography', 'who' => 'photographer', ],
		'presg' => [ 'name' => 'presenting', 'who' => 'presenter', ],
		'video' => [ 'name' => 'video', 'who' => 'videographer', ],
		'writg' => [ 'name' => 'writing', 'who' => 'writer', ],

		'carpt' => [ 'name' => 'carpentry', 'who' => 'carpentry', ],
		'drywl' => [ 'name' => 'drywall', 'who' => 'drywaller', ],
		'elect' => [ 'name' => 'electrical', 'who' => 'electrician', ],
		'mason' => [ 'name' => 'masonry', 'who' => 'mason', ],
		'mecha' => [ 'name' => 'mechanical', 'who' => 'mechanic', ],
		'plumb' => [ 'name' => 'plumbing', 'who' => 'plumber', ],
		'weldg' => [ 'name' => 'welding', 'who' => 'welder', ],
		'roofg' => [ 'name' => 'roofing', 'who' => 'roofer', ],

		// Wha (What)
		'shelt' => [ 'name' => 'shelter', 'who' => 'builder', ],
	];
	return $arr;
}

Tier Four data shows that the "where", "what" and "who" are closely connected. What is the best way to represent this? The roofer needs a roof to roof. The builder needs a building to build. In essence, there are three parts that all work together. If one is missing, then nothing happens. Thus, we are back to the Subejct-Verb-Object model. The data structure here should reflect that.