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1.  IQ is a special purpose domain for listing the target, minimum and maximum quantities of both

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1. tobacco ingredients and non-tobacco ingredients of a tobacco product.

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1. These values represent design specifications, not test data. IQ additionally shows the function of each ingredient by component in which the ingredient appears.
2. IGDCMPID represents the unique ingredient name established in either the Tobacco Ingredients (IT) domain or the Non-Tobacco Ingredients (IN) domain. Therefore, every value of IDGCMPID in the IQ domain must have an exact match in either IT or IN (See IT and IN domain specifications/assumptions for more information on those domains). 
3. IQCAT represents whether the ingredient is a TOBACCO INGREDIENT or a NON-TOBACCO ingredient. Populating this variable facilitates checks for conformance to assumption 2. 
4. Ingredients that appear in more than one component of the tobacco product (or which are constituents of a complex ingredient) are quantified separately for each component/complex ingredient in which they appear. The hierarchical relationship of these ingredients is made explicit by the use of the IQPARENT and IQLEVEL variables:
   1. IQPARENT represents the ingredient or component of the tobacco product in which the ingredient (IDGCMPID for the record) appears as a constituent. 
      1. IQPARENT must equal the IDGCMPID of another record in IQ. 
      2. If the ingredient is not a constituent of another ingredient or component (i.e., it is a top-level component with no parent other than the tobacco product itself) IQPARENT is null.
   2. IQLEVEL is an integer that represents the level in the hierarchy of an ingredient's relationship to other ingredients.
      1. Every ingredient, including top-level ingredients as defined in assumption 4aii above, must have a value for IQLEVEL.
      2. Top-level ingredients have IQLEVEL = 1
      3. Constituents of complex ingredients have IQLEVEL = n+1, where n equals the IQLEVEL of the parent ingredient or component.
5. IQFUNCT is used to represent the function of the ingredient in the component in which it appears (e.g., FLAVORANT, ADHESIVE)

Language from example page intro that we could also use, if better?

Ingredients that appear in more than one component of the tobacco product are quantified separately for each component. IQPARENT and IQLEVEL are used to identify the component/ingredient of which the ingredient in a record is a constituent component, and and at which level in the overall hierarchy the constituent ingredient appears. The following implementation rules apply:

• IQPARENT must correspond to a value of IGDCMPID in the same dataset. If parent is null, the ingredient is considered a top-level component and is assigned a value of "1" in IQLEVEL.
• Records describing ingredients that are constituent ingredients of another ingredient/component listed in the dataset will have IQPARENT value equal to the IGDCMPID of that ingredient/component. IQLEVEL will be set to n +1, where n=the parent record's value of IQLEVEL. 
• Every value of IGDCMPID used in the IQ dataset must have a matching value of IGDCMPID:
  • In the IT dataset (when IQCAT=TOBACCO INGREDIENT) or,
  • In the IN dataset (when IQCAT=NON-TOBACCO INGREDIENT)
  • Therefore, IQCAT is required to relate ingredient quantity records in IQ to the associated ingredient attributes described in either IT or IN.

The use of IQLPARENT and IQLEVEL help make explicit the relationship between complex ingredients and their constituents, and can assist when totaling the quantities of an ingredient that appears in multiple components of a tobacco product. 
The concept map below illustrates the representation of the hierarchical relationships between a complex ingredient and its constituent ingredients in the IQ domain structure. 

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