mysql - Is this the right way to passively assign categories to an entity -

i trying design database can used 'passively' identify (and optionally assign) any/all categories object fits into. below way i'm implementing not having done before, wanted see if has better idea of how go doing it. using symfony mysql , doctrine.

1/. tables define objects:

an element table contains features animal have. table evolve on time - eg animals have wings added:

id name   criteria 1  leg    0-100 2  arm    0-2 3  pouch  boolean 4  horn   0-2 

an animal table give individual information on each animal in database:

id name      gender weight dob 1  gertrude  f      450    2010-01-01 2  shiela    f      200    2008-01-01 3  bruce     m      250    2012-01-01 

an identity table assign elements assigned each animal:

animalid  elementid count description 1         1         4      1         4         0                        2         1         2      2         2         2      2         3         true                    // female kangaroo has pouch 3         1         2     strong hind legs 3         2         2      3         3         false                   // male kangaroo has no pouch 

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the above clear with. however, want able passively identify/assign categories current object meets required criteria for. ideally, user filling in form create new animal able see list of categories meeting criteria add/remove element (eg cow, mammal, bovine, quadruped).

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to continue example:

2/. tables define categories:

a class table define required attributes of category:

id name           weightmin weightmax heightmin heightmax agemax 1  adult cow      220       1000      .         200       50 2  kangaroo       .         100       .         .         . 

a class_feature table additionally defines mandatory features of class through one-to-many association additionally required. note: groupid identifies groups of required features , subgroupof identifies if options nested under additional mandatory requirement (such male/female cows having horns):

classid groupid subgroupof elementid  gender min   max 1       1       .          2          .      0     0        // cow can't have arms 1       2       1          4          m      1     2        // male cows have horns  1       2       1          4          f      0     0        // female cow can not have horns 2       1       .          3          m      0     0  2       1       .          3          f      1     1