About pare Coding

p (present) = IAWA feature number can be present or unknown(?) or varies(v)
The IAWA feature number must be present, unknown(?), or varies(v) in the result set, if the IAWA feature number was followed by the letter p in the search criteria.

a (absent) = IAWA feature number can be absent or unknown(?) or varies(v)
The IAWA feature number must be absent, unknown(?), or varies(v) in the result set, if the IAWA feature number was followed by the letter a in the search criteria.

r (required present) = IAWA feature number must be present
The IAWA feature number must be present in the result set, if the IAWA feature number was followed by the letter r in the search criteria, woods with the feature ? or v in the database will not be returned as matches.

e (required absent) = IAWA feature number must be absent
The IAWA feature number must be absent in the result set, if the IAWA feature number was followed by the letter e in the search criteria, woods with the feature ? or v in the database will not be returned as matches..

Caution: Particularly for the quantitative features (vessel diameter, vessels / mm2, ray width), when trying to identify an unknown, if you code one of the features in a set of related features (multistate characters) present, do NOT code the adjacent feature absent. For example, there are species in which some samples clearly have exclusively uniseriate rays (feature 96) while others clearly have rays 1-2 seriate (feature 97). The database description for such species will have "96 97". So if you code 96 p (uniseriate rays present) and 97a (rays 1-3 seriate absent), this species would be eliminated.

For this type for variability it seems best to have the description include both features present (96 97), rather than code 96v 97v as if you coded 96r or 96e the species would be eliminated. [4 May 2009 - I'm checking the descriptions of the 96v 97v types now to determine how best to have the description set to avoid the r or e elimination problem.]

Caution: Wood is variable and many of the records in the database were based on only 1 or a few wood samples. Consequently, the wood you are working with, even though it might belong to a species in the database, may differ somewhat from the description in the database. Moreover, wood anatomists vary in how they interpret the wood features. Thus, in describing an unknown wood, allowing mismatches can be useful. If the 1st search of the database yields no results, then we recommend that you try the search again using mismatches.

Using 0 mismatches (the default) results in a list of woods with all of the descriptors you used in your search criteria.

Allowing 1 mismatch results in a list of woods with all of the descriptors you used and woods with all but 1 of the descriptors. Allowing 2 mismatches results in a list of woods with all of the descriptors you used and woods with all but 1 or 2 of the feature items..... etc.

When describing an unknown wood, often there are feature numbers that you are sure of their presence or absence and consider important and you would want the search results to list species that matched those particular feature numbers.

For example, if you were sure that a modern wood had simple perforation plates (IAWA feature 13) and did not have homocellular rays (IAWA feature 104), the coded description of the wood could look like this: 1p 5p 13r 104e 136p 142p