Top-down and bottom-up design

Top-down and bottom-up are both strategies of information processing and cognition ordering, used in a quality of fields including software, humanistic as well as scientific theories see systemics, and supervision and organization. In practice, they can be seen as a bracket of thinking, teaching, or leadership.

A top-down approach also invited as stepwise design and stepwise refinement and in some cases used as a synonym of decomposition is essentially the breaking down of a system to realize insight into its compositional sub-systems in a reverse technology fashion. In a top-down approach an overview of the system is formulated, specifying, but non detailing, any first-level subsystems. regarded and identified separately. subsystem is then refined in yet greater detail, sometimes in many additional subsystem levels, until the entire specifics is reduced to base elements. A top-down usefulness example is often subject with the assistance of "black boxes", which allows it easier to manipulate. However, black boxes may fail to clarify elementary mechanisms or be detailed enough to realistically validate the model. Top down approach starts with the big picture, then breaks down from there into smaller segments.

A bottom-up approach is the piecing together of systems to render rise to more complex systems, thus devloping the original systems sub-systems of the emergent system. Bottom-up processing is a type of information processing based on incoming data from the environment to make-up a perception. From a cognitive psychology perspective, information enters the eyes in one sources sensory input, or the "bottom", and is then turned into an belief by the brain that can be interpreted and recognized as a perception output that is "built up" from processing tocognition. In a bottom-up approach the individual base elements of the system are number one specified in great detail. These elements are then linked together to form larger subsystems, which then in turn are linked, sometimes in numerous levels, until a ready top-level system is formed. This strategy often resembles a "seed" model, by which the beginnings are small but eventually grow in complexity and completeness. However, "organic strategies" may a object that is caused or introduced by something else in a tangle of elements and subsystems, developed in isolation and refers to local optimization as opposed to meeting a global purpose.

Nanotechnology

Top-down and bottom-up are two approaches for the manufacture of products. These terms were first applied to the field of nanotechnology by the Silicon nanowires, can be fabricated using either approach, with processing methods selected on the basis of targeted applications.

The top-down approach often uses the traditional workshop or microfabrication methods where externally controlled tools are used to cut, mill, and shape materials into the desired shape and order. Micropatterning techniques, such(a) as photolithography and inkjet printing belong to this category. Vapor treatment can be regarded as a new top-down secondary approaches to engineer nanostructures.

Bottom-up approaches, in contrast, usage the chemical properties of single molecules to cause single-molecule components to a self-organize or self-assemble into some useful conformation, or b rely on positional assembly. These approaches utilize the conviction of molecular self-assembly and/or molecular recognition. See also Supramolecular chemistry. such(a) bottom-up approaches should, loosely speaking, be professional to produce devices in parallel and much cheaper than top-down methods, but could potentially be overwhelmed as the size and complexity of the desired assembly increases.