There has been a significant effort to analyze, design and implement the information systems to process the information and data, and solve various problems. On the one hand, complexity of the contemporary systems, and eye-catching increase in the variety and volume of information has led to great number of the components and elements, and more complex structure and organization of the information systems. On the other hand, it is necessary to develop the systems which meet all of the stakeholders' functional and non-functional requirements. Considering the fact that evaluation and assessment of the aforementioned requirements - prior to the design and implementation phases - will consume less time and reduce costs, the best time to measure the evaluable behavior of the system is when its software architecture is provided. One of the ways to evaluate the architecture of software is creation of an executable model of architecture. The present research used availability assessment and took repair, maintenance and accident time parameters into consideration. Failures of software and hardware components have been considered in the architecture of software systems. To describe the architecture easily, the authors used Unified Modeling Language (UML). However, due to the informality of UML, they utilized Colored Petri Nets (CPN) for assessment too. Eventually, the researchers evaluated a CPN-based executable model of architecture through CPN-Tools.