The proposed goal oriented knowledge acquisition and assessment are based on the flexible educational model and allows to implement an adaptive control of the enhanced learning process according to the requirements of student's knowledge level, his state of cognition and subject learning history. The enhanced learner knowledge model specifies how the cognition state of the user will be achieved step by step. The use case actions definition is a starting point of the specification that depends on different levels of learning scenarios and user cognition sub goals. The use case actions specification is used as a basis to set the requirements for service software specification and attributes of learning objects respectively. The paper presents the enhanced architecture of the student self-evaluation and on-line assessment system TestTool. The system is explored as an assessment engine capable of supporting and improving the individualized intelligent goal oriented self-instructional and simulation based mode of learning, grounded on the GRID distributed service architecture.