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188. Formal methods or verification of application software is performed in which of the following phases of system development life cycle (SDLC)?

a. Initiation and development

b. Development and implementation

c. Implementation and operation

d. Operation and disposal

188. a. The purpose of formal methods is to check whether software fulfills its intended function. It involves the use of theoretical and mathematical models to prove the correctness of a program without executing it. The requirements should be written in a formal specification language (for example, VDM and Z) so that these requirements can then be verified using a proof of correctness. Using this method, the program is represented by a theorem and is proved with first-order predicate calculus. A number of assertions are stated at various locations in the program and are used as pre- and post-conditions to various paths in the program. The proof consists of showing that the program transfers the pre-conditions into the post-conditions according to a set of logical rules, and that the program terminates.

189. Which of the following techniques cannot be used in all phases of a system development life cycle (SDLC)?

a. Prototyping

b. Reviews

c. Simulation

d. Walkthroughs

189. a. The purpose of prototyping is to check the feasibility of implementing a system against the given constraints and to communicate the specifier’s interpretation of the system to the customer to locate misunderstandings. A subset of system functions, constraints, and performance requirements are selected. A prototype is built using high-level tools and is evaluated against the customer’s criteria; the system requirements may be modified as a result of this evaluation. Usually, prototyping is used to define user requirements of the system.

A review is a meeting at which the requirements, design, code, or other products of a software development project are presented to the user, sponsor, or other interested parties for comment and approval, often as a prerequisite for concluding a given phase of the software development process. A review is usually held at the end of a phase, but it may be called when problems arise.

Simulation is used to test the functions of a software system, together with its interface to the real environment, without modifying the environment in any way. The simulation may be software only or a combination of hardware and software.

A walkthrough is an evaluation technique in which a designer or programmer leads one or more other members of the development team through a segment of design or code, whereas the other members ask questions and make comments about technique and style, and identify possible errors, violations of development standards, and other problems. Walkthroughs are similar to reviews but are less formal.

190. Techniques such as prototyping and simulation cannot be used in which of the following phases of a system development life cycle (SDLC)?

a. Initiation

b. Development/acquisition

c. Implementation

d. Operation/maintenance

190. d. The purpose of prototyping is to check the feasibility of implementing a system against the given constraints and to communicate the specifier’s interpretation of the system to the customer to locate misunderstandings. A subset of system functions, constraints, and performance requirements are selected. A prototype is built using high-level tools and is evaluated against the customer’s criteria; the system requirements may be modified as a result of this evaluation. Usually, prototyping is used to define user requirements and design of the system. Simulation or modeling is used to test the functions of a software system, together with its interface to the real environment, without modifying the environment in any way. The simulation may be software only or a combination of hardware and software. A model of the system to be controlled by the actual system under test is created. This model mimics the behavior of the controlled system and is for testing purposes only. Although prototyping and simulation can be used in the system maintenance phase, the payback would be less than the development phase. Usually, the scope of system maintenance can be small and minor, making it cost-prohibitive to the use of prototyping and simulation techniques.

191. Which of the following require an extensive testing effort in an application system integration project?

a. Regression testing

b. Interoperability testing