As research and identification went ahead a category structure evolved.
Giving descriptions here, almost in way of a glossary, should avoid any confusion later on!
Because there is a mixture of “coded symbols”, representations of, for example, animals, birds and people plus readily discernible items such as Crosses, the category structure needed to accommodate all types of carving on every Class 1 and Class 2 Stone. Therefore, every carving is called an Object and every object has a specific name e.g. Beast With Exaggerated Claws, Triple Disc etc. Where applicable, the words commonly used in books on Pictish Stones and other relevant texts and websites have been retained e.g. Mirror, V-Rod etc.
Several types of object can be classified together as an Object Category e.g. the Bird object category comprises eagle, goose, bird with exaggerated claws and indecipherable bird.
Some objects have specific broad Patterns such as the Mirror Case which is either hollow or solid.
Every object is to a Design. More than one instance of an object might be to the same design. For example, the Mirror design at Abdie is the same as those at Kinblethmont, Inveravon (2) and Knockando (2).
Those designs that look alike can be gathered together into a Group of Designs. So among the Serpent objects, for example, there is a group of designs that are similar to one another such as Serpent Group 2 in which each serpent has a Z-Rod across it.
So a structure falls into place as:-
Object Category – Object – Pattern – Design – Group of Designs
Needless to say not every object will fall into a pattern, nor is there commonality of design for some objects; a good example being the V-Rod & Crescent – each design is unique. Conversely the Pictish Beast carvings are almost identical in style, the only variants being left or right facing and angle of incline.