According to Robert (1996), knowledge can be very difficult concept to define. Indeed, a whole branch of philosophy is given over to question about knowledge. On the other hand, ‘knowledge’ is a word we all use and understand in everyday life without much trouble. So, he defined the knowledge as comprises the facts, rules, models and concepts that underpin the day-to-day decisions made at every level in the organization. For example:
 Facts: Felix is a cat, a cat is a mammal;
 Rules: if x is y and y is z, then x is z;
 Models: class hierarchies, classification of animals;
 Concepts: cat, mammal, class, class membership
According to him,
Knowledge can be explicit or tacit, for example:
 Explicit: “I like meat, I don’t like fish”;
 Tacit: “I don’t know what I want but I’ll know when I see it”
Burlton (1998), said ‘Explicit’ knowledge is an articulated knowledge you can see, read and use, while ‘Tacit’ knowledge is what’s in people’s heads. Oftentimes people don’t know what they know.
Sometime it is very difficult to make tacit knowledge explicit, which you need to be able to do to understand, explain, test or teach it
Knowledge can be deep or shallow, for example:
Deep: “I gave the patient these pills because he had symptoms which indicate a certain condition that the pills are effective against”
 Shallow: “If you’ve got a cough, try cough linctus”

Knowledge is formulated in the minds of individuals through experience. People learn, naturally, all time, through shared experience and through the transfer of knowledge, both tacitly and explicitly. Every individual and community has a pool of ‘general’ and specific knowledge. Every task or skill has specific knowledge associated with it.

In Alvesson’s research (1999), he stated that knowledge is a very difficult to understand. It may be divided up into information (simple, fragmented kind of knowledge), knowing (how to do), explanation (knowledge answering why? what is behind? what is the cause?) and understanding (knowledge, referring to patterns, connection, providing gestalt of phenomenon).
According to Oxford dictionary, knowledge is a person’s range of information or sum of what is known.
Since knowledge is infinite, it is not ‘consumed’ in the way we consume raw materials. Knowledge is not depleted when it sold or used but actually multiplies through use. The nature of knowledge as a resource in the new economy is so different that there is a phenomenal growth of attention of knowledge development and management.
Alle (1999), in her research sees knowledge as complex system that can be viewed as the following principles:

a. Knowledge is ‘messy’
In organizations, every aspect of knowledge is connected to everything else. You cannot neatly isolate the ‘knowledge’ component of everything. Organizational knowledge relates to cultures, technology and the unique configuration of individuals that make up the organization.

b. Knowledge is self-organizing
Every day, knowledge is created, sustained, killed off (which appropriate to current use and need to dispose off) and renewed in an organization. Knowledge has little of its owns and it is a self-organizing entity. The ‘self’ that knowledge organizes around is organizational or group identity and purpose.

c. Knowledge seeks community.
Knowledge wants to happen just as life wants to happen and both want to happen as community. Communication of knowledge is so powerful that they now involve people in conversation with each other all over the globes.

d. Knowledge travels on language.
Language is the verbal blue print of our experiences. Without a word experience or language to describe our experience we cannot communicate what we know. Every mode of knowledge travels on a different language. Language initiates us into particular world of experience.

e. Knowledge is slippery.
The more you try to pin knowledge down, the more it slips away. It is tempting to try to tie up knowledge as codified knowledge, document, patents, intellectual property, libraries, and databases. When too much rigidity and formality lead to unwanted side effect of stifling creativity and new knowledge development.

e. Loser is probably better.
Highly adaptable systems look sloppy but the survival rate of diverse, decentralized systems is higher. This means we can waste resources and energy trying to control knowledge processes too tightly.

f. Knowledge keeps changing.
There is no final solution in knowledge management. The patterns of knowledge are always changing. The best approach or solution is one that keeps things moving along while keeping options open.

g. Knowledge does not grow forever – eventually dies / lost.
Number of people in knowledge hold that knowledge is continuously grows. Constant growth does not hold true in nature and it does not hold true for knowledge.

h. No one really in charge.
Knowledge is a social process. Only people together make knowledge happens. No one person can take responsibility for collective knowledge. Knowledge managers cannot manage knowledge itself. However. They can and do help devise and manage process for acquiring creating, sharing and applying knowledge.

i. You cannot impose rules and system.
If knowledge is truly self-organizing, then the most important way you can advance it is to remove the barriers to self-organization. Ti will take care itself.

j. There is no silver bullet.
No best practice to advance knowledge and expand organizational intelligence. It must be supported at multiple levels. It requires a system approach, careful thought, reflection, and experimentation and constant adjustment.

k. How you define the knowledge ‘problems determines what and how you try to manage.
The knowledge question can prevent itself in many ways. If organization is concerned with ownership then focuses on acquiring codified knowledge that can be protected with copyright and patents.

l. Knowledge can be obsolete
Knowledge that can used today maybe can’t be used after some time and can be obselete.

Although the principles stated do not govern all aspect of knowledge, organization still advance in other ways that may support the creating, satisfying, sharing and renewing of knowledge.