Top-Down and Bottom Up Processes

The process of starting with world objects and modeling using entity-relationship diagrams is referred to as a top-down process. Starting with one large table and functional dependencies using normalization is referred to as bottom-up development.

What are the advantages and disadvantages of each method? Are there any inherit dangers with either method? Which would you prefer to use? Is it really an either-or situation?

Top-Down and Bottom Up Processes

Top Down
Top-Down is deductive reasoning. It can be used in conjunctions with analysis and decomposition. Breaking down a system to gain insight into different elements is the top-down approach. First a total system is developed, and then subsystems are detailed.
There may be many different levels until everything is reduced to a whole. To put it in simple terms, top-down approaches start with the big picture. This concept is broken down into smaller segments for ease of understanding and learning.

In business top down can be illustrated by leadership, business integration, processes, learning and data. Leadership requires an excitement level about improvement processes. Leaders believe that there are processes that can improve the company. Business integration is communication about the new initiative. Processes designate a small team that begins to map current processes from the top to the bottom.  Learning is the process where training in the improvement issues are presented to the entire company. Data gathering at this point in the process is just beginning.

An advantage of top-down reasoning includes the clear statement from executive. Training is given to numbers of employees and a communication is built. There is a full list of process and documentation is required.

Challenge is time. There are many activities, but the analyzing and improving processes are slow yet thorough. Training gives the tools and concepts, but not actual work. Basically there is little change with top down reasoning.

Bottom Up
Bottom up is inductive reasoning. The original idea is the sub-set of the emerging system. This is an information process based on data coming in from difference sources to form a perception. Information processing is determined on incoming data from outside and. individual base elements are described in great detail.

All systems are linked until a complete system is formed. Think of bottom-up as a seed. The beginnings are small but they grow in complexity to form the whole.
Leadership is connected and engages employees in improvement efforts. 
Managers determine what processes in their department needs to be fixed and assign employees to "fix" the processes. Most processes are narrow with improvements implemented in only one area. The learning is hands on training either from a manager, vendor, or professional training organization. Data is real-time and the problems are known up front.
As the process improves the team knows the results, but actual data is limited.

Utilizing the bottom-up approach, changes can be researched and implemented immediately.  Efforts are focused on specific defects and problems and learning is focused on real work problems.
Small improvement in processes and thinking are made quickly, but widespread changes take quite a bit of time to be recognized and utilized.

There is no strategy for focus and improvements generally do not have a huge impact on the entire company. Improvement scan spread, but they can also die quickly. Managers can only fix their own departments (Sweet, 2011).

There is no right or wrong method in reasoning. If your company wants changes in processes to be slow and steady use top-bottom reasoning. If you need quick fixes in departments, bottom-up may be the best approach. Mix the two processes together to come up with the real answers.

References
Sweet, Shelly (2011). Which is Best for Us? Top-Down, Bottom-Up or Middle Out? Available: http://www.i4process.com/publications/which-is-best-for-us-top-down-bottoms-up-or-middle-out/. Last accessed: 3 April 2013.

Elad Shalom,
Senior Consultant at SwiftRadius