The concrete architecture at a given level is normally defined in the phrase of its components. Hence, the description of the concrete architecture at a given level is based on the abstract architectures of its components.
As an effect, the concrete architecture at a specific level is a description at a higher abstraction level than the corresponding abstract architecture at the subsequent lower level.
Thus, we can define that the sequence of theory of concrete and abstract architectures at successive levels yields a description framework at following higher levels of abstraction.
Therefore, the three-level architecture description design considered, with independent concrete and abstract views at each level, and it supports a six-level hierarchical description scheme.
Hence, the subsequent levels – the concrete and abstract architecture at the micromachine level, the concrete and abstract architecture at the processor level, and the concrete and abstract architecture at the system level – are levels with an increasing degree of abstraction.
Specific computer architectures are generally represented consistently, for instance in processor textbooks, the usage of a convenient method of presentation. An informal description is also used in most papers offering a new architecture or in papers evaluating current architectures.
However, a formal description is needed if a definite, unambiguous representation is required, including for inputting architecture specifications into a CAD package.
This can be needed to implement verification, simulation, or analysis depends on the given structural or behavioral description. The typical technique of formally describing an architecture is by utilizing an architecture description language (ADL).
ADLs are also known as hardware description languages (HDLs), or computer hardware description languages (CHDLs). An additional concept, which is also used, is register-transfer languages (RTLs).
RTL designates a specific type of ADL, which is constrained to the processor level. Sometimes, ADLs and HDLs will be exclusively based on the level of abstraction they cover. HDLs are treated as low-level and ADLs as higher-level description languages.