SAP Classification system can be very powerful tool to provide additional information to your master data. It can be used for classifying and subsequent searching objects based on given set of characteristics describing the object.
Also with using classification system you can extend your master data without modifying the master data tables!
Classification “metadata” hierarchy
On the top of Classification structure hierarchy there is a Class Type (sometimes also called Object Type). This represents an object type, e.g. Material, Batch, Vendor, …
For each Class Type there can be 0..N Classes created. Classes are used to group similar properties/attributes of an object, e.g. color, dimensions, quality certificate, …
In Classification system, these properties are called Characteristics. This means that each Class can contain 0..N Characteristics. Actually a Class containing no Characteristic is quite useless so it makes sense to always have at least one Characteristic in a Class.
Each Class must always be assigned to a Class Type. It can also define its “super/parent class” (you can also do it vice versa – you define “child classes” of a “parent class”) – this gives possibility of building an inheritance tree where all “parent class’s” characteristics are inherited in each of its “child classes”. The “child class” can be further extended with another extra characteristics… so you can create quite flexible data structure.