Sea Technology

JAN 2014

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Navigation

Page 46 of 71

(Top) Concept diagram of ISO/IEC25010 showing the relationship between software, data and system quality-in-use models. (Bottom) Software-related challenges when providing realtime water level information under the e-Navigation concept of operation. quality assurance is the reported anomalies that have occurred with electronic chart display and information systems (ECDIS). Due to the complex nature of ECDIS, i.e., a mix of hardware, software, sensor inputs and data, the cause of the anomalies are not always apparent. However, software is usually a factor. As reported to IMO in 2011, the International Hydrographic Organization (IHO) expressed concern that there was no specifc obligation for ship operators to keep software up-to-date for increasingly sophisticated computer-based systems. As a result, in 2012 IMO issued a draft Safety of Navigation Circular on "Operating Anomalies Identifed within ECDIS." In addition, IMO is looking into developing a policy on the working-life validity of software-driven electronic navigation equipment. ISO Standards One way to achieve consistency and uniformity is to conform to relevant international standards. In particular, there are signifcant benefts when there is compliance with standards established by the International Organization for Standardization (ISO). ISO has adopted software quality standards for avionics, automobiles and medical equipment/devices. Safety-critical systems are those in which defects could have a detrimental impact on humans, the environment or assets. Depending on software functionality requirements, these systems are expected to verify specifc qualities, in- cluding reliability, availability, security and safety. ISO has published several standards related to software quality with regard to product, development process and quality-in-use. ISO/IEC 9126-1 classifes software quality as a structured set of characteristics. Each quality characteristic and associated subcharacteristics (e.g., attributes) needs to be measured (i.e., metrics). Reliability is a set of attributes that relate to the capability of software to maintain its level of performance under stated conditions for a given period of time. Usability is a set of attributes that describe the intended use, and that this use meets the needs of intended users. Effciency is a set of attributes dealing with the relationship between the level of software performance and the amount of resources required. Maintainability is a set of attributes that describe what is necessary to maintain required software performance. Portability is a set of attributes dealing with the capability of software to be transferred from one environment to another. ISO/IEC 12207 describes the process of developing software product from analysis of user requirements to procurement of software product, including necessary processes and activities that should be applied during the acquisition and confguration of the system. It also specifes system operation and maintenance, and includes quality assurance. ISO/IEC 15504, also known as SPICE (software process improvement and capability determination) can be used to improve the software development process. Automotive SPICE for automobiles and SPICE 4 SPACE for aircraft have been accepted as domain-specifc models. CMMI (capability maturity model integration) is another worldwide practical model introducing these standards. In particular, ISO/ IEC 15504 is actively supported by the U.S. Department of Defense. Recently, the SQUARE Project (software product quality requirements and evaluation) was conducted by ISO to remove redundancy between legacy standards (e.g., ISO/IEC 9126-1). The ISO/IEC 25000 series is the output of SQUARE and represents the most up-to-date international standard on which to base SQA guidelines for e-Navigation. ISO/IEC 25010 defnes the required quality models, including a Data Quality Model, Software Quality Model and Quality-in-Use Model. Implementing SQA in e-Navigation Software development will become a key determining factor infuencing the implementation of e-Navigation. While high-quality software should be the goal, this does not always occur since development cost is always a consideration. Rather than the best quality, it is more important to ensure a suffcient level of quality for critical software. The concept of ft-for-purpose is usually determined on an individual equipment or system basis. However, e-Navigation requires interoperability between shipborne and shorebased equipment/systems, and needs to be included in the total software budget. To achieve the goals of e-Navigation, advanced software development will need to fully integrate the functions of www.sea-technology.com January 2014 / st 47

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