The modeling process aims to define and analyse requirements for testing physical scale systems such as robotic surgery machines, railway signalling and control systems, nuclear reactor control systems, etc... These safety-critical systems whose failure may result in severe human or physical damage, are designed to be testable and verifiable before their implementation. To understand the system specifications and its functionalities, different types of models are used and each one reflects a viewpoint of a particular scope. Furthermore, its aim is to risk analysis and performance testing. Our approach is based on goal-oriented requirements elicitation, structuring and analysis. To automate the latter requirements engineering processes it is crucial that we involve expert knowledge. This process needs to be split into several steps. This work is limited to present techniques to obtain specifications dependency graphs from a set of requirements to determine the global goal model. This paper presents a domain independent framework for operational requirements modeling beside of specifications structuring technique based on Guidance Ontology. The present work focuses on improving the performance of structuring techniques through a pattern recognition based on a guidance ontology. This approach is shown to enable the structuring process automation by making use of domain ontologies as an expert knowledge base and capitalization.