The extraction is the process of removing or obtaining something from something else; whether with force or difficulty, or chemically. It is a one of separation technique used in most science researches. In our research focusing, extraction process is the process of converting captured notation information into data. Our proposed approach for notation extraction will play an important role in assessment process later. Notations differ in their extraction depending on their keyword and text structure in Rational Rose petal files. An ideal notation extraction process can digest target Rational Rose file that are visible only as petal file pages, and create a local replica of those tables as a result. Proper notation extraction also requires solid data validation and error recovery to handle data extraction failures. Extraction process should be as accurate and reliable as possible because its results will be used as a base to develop an Assessment system for UML Class Diagram. This paper discusses the extraction process from Rational Rose petal file that represents the structure for each notation of UML class diagram as a text form. The UML class diagram of notations have involved are class object notation, inheritance notation and relationship notation such as Association, Association class, generalization, aggregation and composition. Each notation which is extracted will keep as a data in a few tables. All these tables will be accessed in assessment process later to implement the UML Class Diagram Assessment System that proposed in our main research.