Diverse software

The confirmation or refuting of a structure require that there is a chemical structure postulate. Any such decision is subject to errors, in particular those imposed by chemical shift prediction errors. A more robust decision can be made if the spectrum is not only compared against the postulate (where it exists) but also a series of closely related compounds. Such a list is most likely to originate from chemical diversity software or prior chemical knowledge. 

BIOSTAR Tripos Inc. (St. Louis, MO, U.S.A.) Macintosh -based (4-DL) Around S20K Compound registration, assay assignment, data analysis, data storage and retrieval, easy interface with chemical structure and diversity software offered by Tripos Only on Macintosh, difficult to customize, cannot execute cross-plate operations... 

OpenLynx Diversity Software, Micromass, Waters Corporation. http //www.micro-mass.co.uk/... 

The initial design phase for combinatorial compound collections focuses on computer-generation of a virtual library and selecting a subset of compounds for chemical synthesis on the basis of specific characteristics, such as maximum diversity, desired lipophilicity, and lack of toxic and reactive functionality [13]. When combinatorial compounds are used for lead optimization, collections can be designed on the basis of a reference structure with the collection chosen to represent the desired degree of diversity. Software for the design of such combinatorial reactions is commercially available. An alternative ap-... 

The provision of redundant hardware and diverse software theoretically gains significant risk reduction (5% x 5% =. 05. 05 = 0.0025 failure probability (99.75% success)) However, care must be taken to identify common mode failures such as power supplies, fire etc. Generally, a good SIL 2 system claim can be defended using two SIL 1 systems. 

Use diverse software channels or diverse technology channels with appropriate comparison diagnostics to minimize the impact of systematic errors in the application software. This may involve the use of the application software in the BPCS to emulate the SIF logic (e.g., mirroring, shadowing), providing continuous compare of BPCS and SIF states with appropriate action (e.g., alarming or manual shutdown), as needed. 

The extent to which software can be made diverse and free from common cause failures is not fully resolved. The use of diverse software in redundant systems (discussed in more detail in Section 9) can reduce the probabihty of common cause failure in comparison with the use of identical software. However, there is no way to... 

The diverse software problem. In extremely high-reliability systems such as nuclear reactor shutdown systems, as we shall see, two diverse high-integrity protection (safety) systems may be required. The question is, is it alright for... 

When there are two "N. diverse software-based systems, does it actually improve the risk of software common-mode failure ... 

This is a very detailed and thorough standard which is used in civil avionics to provide a basis for certifying software used in aircraft. Drafted by a EUROCAE/RTCA committee, DO-178B was published in 1992 and replaces an earlier version published in 1985. The qualification of software tools, diverse software, formal methods, and user-modified software is now included. 

P Bishop et al. "Project on Diverse Software - An Experiment in Software Reliability". Proc. 4th IF AC Workshop, Como, Italy,... 

It is considered that the concept of error-free software cannot currently be realised in any but the simplest of programs and hence measures to reduce the possible effects of software errors are taken. The design intent adopted is that no single software error is to invalidate more than one line of protective logic. Diverse software production methods between channels are specified in order to meet the intent. If achieved, this reduces the possibility of software induced CMF to the level of random, coincident residual faults. In a numerical sense the design intent is that software faults shall not compromise the assessed CMF reliability measures discussed in the previous section. Since quantitative demonstration of achievement cannot be made qualitative aspects of the methods of software production, discusaed briefly below, are assessed and lead to the judgement that dependent, software faults in both channels leading to a potentially unsafe condition can be discounted. 

As for software, the same diversity as explained for hardware is required. The connection of the diverse software channels has to be achieved by small, fully tested programs or hardware. 

PEI and PE2 based on diverse software and, unless certain conditions apply, diverse hardware... 

If we consider these recommendations we often end up with separate C files, which realize the desired functionalities and others that realize the safety mechanisms. By using partitioning (separation of functions and functions monitoring by safety mechanisms), which can also already be implemented in the system architecture level, the complexity can be strongly reduced. A mix of safety relevant functions and non-safety relevant functions at the software design level, which is inside of a SW unit, is actually not considered in ISO 26262. The SW-Unit would have to be developed according to the highest ASEL. This could then lead to an issue with ASIL D, since at this point redundancies or an implementation of diversity software is recommended. 

All systems need to be sufficiently reliable and secure in delivering the service that is required of them. Various ways in which this can be achieved in practice range from the use of various validation and verification techniques, to the use of software fault/intrusion tolerance techniques and continuous maintenance and patching once the product is released. Fault tolerance techniques range from simple wrappers of the software components [1] to the use of diverse software products in a fault-tolerant system [2]. Implementing fault tolerance with diversity was historically considered prohibitively expensive, due to the need for multiple bespoke software versions. However, the multitude of available off-the-shelf software for various applications has made the use of software diversity an affordable option for fault tolerance against either malicious or accidental faults. 

Littlewood, B., Popov, P., et al. Modelhng the effects of combining diverse software fault removal techniques. IEEE TSE SE-26(12), 1157-1167 (2000)... 

---