Software life-cycle

The software life cycle activities extend until retirement of the software. However, in a manner of speaking, life cycle activities extend even beyond retirement since the data must be able to be reconstructed at any time during the life of the product, i.e., the archived record must always be accessible and readable even if the software is no longer commercially available or typically employed in the laboratory. Additional software validation includes implementation of the code and integration and performance testing. There also must be system security, change control procedures, audit trails, calibration, preventative maintenance, and quality assurance. 

Guidances recommend an integration of software life-cycle management and risk management activities. Software validation and verification activities must be conducted throughout the software life cycle [12,14]. Software verification and validation are terms frequently confused. Software verification is defined as the process that provides objective evidence that the design outputs of a particular phase of the software development life cycle meet all of the specified requirements for that phase... 

ISO1207 1995, Information technology—Software life cycle processes. 

ANSI/AAMI SW68 2001, Medical device software—Software life cycle processes. ... 

The cost of total system maintenance and enhancement is currently shared by over one hundred laboratories, reducing the cost and raising to overall system quality as compared to in-house efforts. Proven time and time again by software life cycle, this package is highly superior to any custom written system for long term support and lower acquisition cost. 

The firm has failed to establish an overall revision control system for the program thronghont its software life cycle. [FDA 483, 2001]... 

Defines the appropriate software life-cycle method to be followed... 

ANSI/AAMI SW68. Medical Device Software—Software Life Cycle Processes Association for the Advancement of Medical Instrumentation, 2001. 

ISO/IEC 1207. Information Technology—Software Life Cycle Processes ISO/IEC, 1995. 

The software life cycle starts with a requirements analysis and product definition. These define the require-... 

The manufacturing department ships the product in accordance with manufacturing guidelines, based on the receipt of valid purchase orders. The product documentation includes a Declaration of System Validation with statements from Hewlett-Packard that the software was developed and tested according to the Hewlett-Packard Analytical Software Life Cycle, a process that has been certified for ISO 9001 quality standard and for the information technology quality system (ITQS) compliance and that has been inspected by representatives from both computer validation companies and the pharmaceutical industry. 

Most expert-system development efforts will also follow the five phases of the conventional life cycle with heavy emphasis on knowledge acquisition and representation in the design phase. Several of the V V procedures outlined in Table I for conventional software life cycle can be applied in ES V V. Table II provides a list of some applicable procedures. Many procedures are simply a part of any software development effort, but are many times overlooked in ES efforts. For example, ES developers oftentimes do not develop adequate requirements documentation. They have difficulty in tracing knowledge representation structures (rule paths, frames, etc.) back to design documents which in turn makes... 

Many of the conventional V V techniques within the conventional software life cycle can either be directly applied to BS development or can be modified to handle the somewhat instructured nature of an ES. Formal unit testing used in conventional software development can also be applied by looking for items such as consistent and complete rules. 

Masters the SOPs for the software life cycle Develops, changes and operates application software Supports users in using the application software Conducts training for the application software... 

The assessment and qualification of software for computer based systems important to safety requires (as e g. in lEC 60880) a set of detailed documents according to the development steps of the software life cycle. For pre-developed software the amount of documentation available and its detail will not be sufficient in most cases. On the other hand, the pre-developed software may have been operating in many applications, and it should be possible to evaluate this operating experience to demonstrate dependability. 

Inspections and reviews Organized meetings to review software components and products with the aim of uncovering errors early in the software life cycle. 

A process model is an ideal definition of the software life cycle or of how actual software projects work. As such, they are prescriptions for how to organize the software engineering activity. In reality, actual software projects deviate from these models but the models nevertheless give both managers and engineers a framework in which to plan and schedule their work. 

FIGURE 1 The waterfall model of the software life cycle. 

Testing consumes a large part of the software life cycle and its budget. Engineers use software tools such as test generators and test execution environments to try to control these costs. 

Another factor that complicates the scheduling and estimation tasks is that requirements for a software system can rarely be specified precisely and completely at the start of a project. The product is often built for an incompletely known environment, possibly for a new market, or to control a novel device. Thus, it is typical for requirements to change throughout the software life cycle. One of the ways to deal with this challenge is to use a flexible process model that requires frequent reviews and incremental delivery cycles for the product. Feedback from the delivered increments can help focus and complete the requirements. 

AR442 1.173 Developing software life cycle processes for digital computer software used in safety systems... 

During software life cycle some mistakes are possible and faults will be experienced not only into the project code but also in specification and/or exploitation. When running the software in a real environment some faults will generate failures or are possible to be used by hackers to control the system. 

Ardi S. 2008. A Model and Implementation of a Security Plugin for the Software Life Cycle, Thesis No. 1353, Linkoping Studies in Science and Technology. 

The software life-cycle management should prevent any unverified changes. The possible failures (item 2.) are in principle similar to pre-accident human errors like miscalibration or mispositioning and could be modelled in the same way if not screened out due to low probabihty. This type of failure is clearly CCF suspected. 

Specific Development Activities. Software life cycle activities related to system safety engineering include the following ... 

This part of the problem involves prediction of software integrity from the character of the methods used in a single phase of a safety software life-cycle presented in a standard such as IEC61508-3. There is some previous work that is relevant to this problem as summarised briefly in section 3. Die network structure in Figure 3 is proposed. 

This view is more conq)lex than previous process-based attempts to capture software reliability using BBNs. It takes the view that a phase is associated with a set of processes (e.g. a requirements specification), and these processes are subject to active updating for the duration of the project due to work in later phases. This approach allows us to capture intricate influences between phases . The generic BBN structure shown in Figure 4 presents a sub-net for each phase of the safety software life-cycle and a net for interaction among phases. The interaction net aggregates integrity estimates from multiple phases. 

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