"knowledge is difficult" is a correct and usable phrase in written English.
It can be used as a subject-verb sentence pattern, where "knowledge" is the subject and "is difficult" is the verb phrase describing the difficulty of gaining or understanding knowledge. Example: "Studying advanced calculus is challenging because knowledge is difficult to grasp without a strong foundation in basic math skills."
All this knowledge is difficult and costly to gather.
This may be because customer industry knowledge is difficult to assess during a recruitment interview or from employer references.
Adequately representing and integrating temporal data and domain knowledge is difficult with the database technologies used in most clinical research systems.
Secondly, although knowledge of the optimal nutritional requirements is useful in designing a media, this knowledge is difficult to apply when economics dictate the use of commercial substrates such as corn steep liquor, soy bean meal, etc., which are complex mixtures of many nutrients.
Implicit knowledge is difficult for teachers to explain explicitly and therefore prosody training is rare in classrooms.
Tacit knowledge is difficult to transfer between people, and is best obtained by being immersed into a group of people who have it (Collins & Evans, [2007]).
Finally, medical decisions of individuals lacking medical knowledge are difficult to interpret.
CBR is a suitable paradigm for microarray analysis, where the rules that define the domain knowledge are difficult to obtain because usually only a small number of training samples are available.
The use of machine learning techniques for the automatic construction of knowledge bases and knowledge representations is difficult, but has achieved some degree of success.
If knowledge ambiguity is high, knowledge itself is difficult to interpret, assimilate, and apply to commercial ends.
This is time-consuming and strenuous, and hence personalized prior knowledge recommendation is difficult to perform.
