Knowledge formalization is transformation of knowledge into formal representation languages such as Ontology Inference Layer (OIL) [19], depends on application. Therefore, the knowledge engineer has to consider the advantages and limitations of the different languages to select the appropriate one. 

## 1.3.4 Evaluation Phase

The main objectives of this phase are to check, whether the target ontology suffices the ontology requirements and whether the ontology based knowledge management system supports or answers the competency questions, analyzed in the feasibility and kick off phase of the project. Thus, the ontology should be tested in the target application environment. A prototype should already show core functionalities of the target system. Feedbacks from users of the prototype are valuable input for further refinement of the ontology. [18] 

## 1.3.5 Maintenance And Evolution Phase

The maintenance and evolution of an ontology-based application is primarily an organizational process [18]. The knowledge engineers have to update and maintain the knowledge and ontology in their responsibility. In order to maintain the knowledge management system, an ontology editor module is developed to help knowledge engineers. 

## 1.4 Case Study

The initial investigations have been done with 10 firms within the two biggest handicraft associations in Thailand and Northern Thailand. Northern Handicraft Manufacturer and EXporter (NOHMEX) association is the biggest handicraft association in Thailand which includes 161 manufacturers and exporters. Another association which is the biggest handicraft association in Chiang Mai is named Chiang Mai Brand which includes 99 enterprises. It is a group of qualified manufacturers who have capability to export their products and pass the standard of Thailand's ministry of commerce. 

The objective of this study is to create a Knowledge Management System 
(KMS) for supporting this handicraft cluster. One of the critical tasks to implement this system is creating ontologies of the knowledge tasks. Because, ontology is recognized as an appropriate methodology to accomplish a common consensus of communication, as well as to support a diversity of activities of KM, such as knowledge repository, retrieval, sharing, and dissemination [20]. In this case, knowledge engineering methodology was applied for ontology creation in the domain of Thailand's handicraft cluster. 

Domain Ontology: can be created by using three models in context level of model suite; i.e. organization model, task model and agent model. At the beginning of domain ontology creation, we adopt generic ontology plus acquired information from the worksheets as an outline. Then, the more information that can be acquired 