面试题与答案

Waterfall is a sequential and non-iterative SDLC model which describes the flowing of phases downwards one by one. The process does not start a phase unless the previous phase is completed once and for all completely. The waterfall model consists of the following phases:

• • Requirements gathering
  • Design
  • Implementation
  • Testing
  • Maintenance 

• Requirements gathering: All the requirements are gathered and analysis is performed for the complete system.
• Design: Various design models are created for the complete system after the requirements gathering phase has been completed and ended.
• Implementation: The complete system is implemented once the design for the system has been frozen.
• Testing: The complete system is tested after all the construction and integration has completed.
• Maintenance: Post implementation support carries out after the implementation of the system. 

The strengths of the waterfall model are:

• No planning needed
• Works well for small projects with fixed and clear requirements.
• Lesser cost as planning overhead is less
• Quickest delivery of the complete system 

Phases of the incremental model are the same as waterfall i.e. Requirements, design, implementation, testing, and maintenance.

However, instead of following the waterfall once and for all linearly, the incremental model takes a different approach. These phases are repeated incrementally as business value is delivered incrementally as well.

For every single phase and increment a waterfall model is followed. The waterfall model is then put in a cycle of increments along with verification of requirements, and design. 

Phases in spiral model:

a) System requirements are identified in detail.
b) An initial design is created for the new system based on the requirements in previous phase. All feasible and technical approaches are identified and analyzed to build the system. The design is done on a very broader and deeper scope to identify and deal with potential risks in the system.
c) A prototype is created depicting a few features of the system.
d) A second prototype is created using 4 steps: Evaluate first prototype, define requirements for second prototype, planning and designing for second prototype, constructing and testing second prototype.

There is no specific SDLC model that can be used for all types of projects and situations. If none of the popular SDLC models suit a specific project then, pick the closest matching SDLC model and modify it as per needs. Identify how important is risk assessment and use spiral's risk assessment methodology if it's a risk-critical project.

The project should be delivered in small chunks, ideally merging the incremental model with the V-shaped model. One must spend ample time choosing the right model or customizing one to suit a project for its successful and efficient completion. 

LLD (Low-LevelLevel Design) is a term that refers to the process of detailing. It provides a full description of each module, including actual logic for each system component and a thorough examination of each module's specifications. Every program undergoes logic design, which is subsequently recorded as program specifications. A unit test plan is prepared for each software. The micro-level or intricate design is another name for it. After the High-Level Design, the Low-Level Design is created.

• It is not a useful method for small development projects.
• It requires an expert to take important decisions in the meeting.
• The cost of implementing an agile method is a little more compared to other development methodologies.
• The project can easily go off track if the project manager is not clear about what outcome he/she wants.