SOFTWARE PROCESSES Flashcards
Give examples of project constraints
staff, money, time, computing resources,
Describe project planning
Project planning is the art of scheduling the necessary activities, in time, space and across staff in order to have in mind:
project risk
profit
customer satisfaction
worker satisfaction
long-tern company goals
What information must a project plan include?
resources needed (people, money, equipment, etc)
dependency & timing of work (flow graph, work packages)
rate of delivery (reports, code, etc)
Give examples of deliverables an SE project must produce to make it more visible
Design documents/ prototypes
Reports
Project/status meetings
Client surveys (e.g. satisfaction level)
What is a software process?
A structured set of activities required to develop a
software system
What steps are a part of all software processes?
Specification – defining what the system should do;
Design and implementation – defining the organization of the system and implementing the system;
Validation – checking that it does what the customer wants;
Evolution – changing the system in response to changing customer needs.
What is a software process model?
A software process model is an abstract representation
of a process. It presents a description of a process from
some particular perspective.
What do software descriptions entail
Activities in these processes such as specifying
a data model, designing a user interface, etc. and the
ordering of these activities
Products, which are the outcomes of a process activity;
Roles, which reflect the responsibilities of the people
involved in the process;
Pre- and post-conditions, which are statements that are true before and after a process activity has been enacted or a product produced.
What are the different types of software process models
Plan-driven processes are processes where all of the
process activities are planned in advance and progress
is measured against this plan. AKA Heavy-weight
In Agile Processes planning is incremental and it is
easier to change the process to reflect changing customer requirements. AKA Light-Weight
Give examples of Heavy-Weight models
Waterfall Model
Boehm’s Spiral Model
V-shaped Model
Describe the waterfall model
Separate and distinct phases of specification and development.
Heavily oriented toward documentation (documentation-intensive)
Progress often measured through documentation completion and reviews (many)
Gantt charts
Lockstep approach
Illustrate the different phases of the waterfall method
*See notes
What are some of the problems involved with waterfall models
Inflexible partitioning of the project into distinct stages
makes it difficult to respond to changing customer
requirements.
But many issues are true too, such as risk addressing.
In which situations is the waterfall model used?
This model is only appropriate when the requirements are well-understood and changes will be fairly limited during the design process.
The waterfall model is mostly used for large systems
engineering projects where a system is developed at
several sites.
In those circumstances, the plan-driven nature of the waterfall model helps coordinate the work.
Describe the Boehm’s spiral model
Process is represented as a spiral rather than as a
sequence of activities with backtracking.
Each loop in the spiral represents a phase in the process.
No fixed phases such as specification or design - loops in the spiral are chosen depending on what is required.
Risks are explicitly assessed and resolved throughout the process.
This was the motivation behind developing the Spiral Model - Risk
Illustrate the Boehm’s Spiral Model
*See notes
What are the sectors of the spiral model sectors?
Objective setting
Specific objectives for the phase are identified.
Risk assessment and reduction
Risks are assessed and activities put in place to reduce
the key risks.
Development and validation
A development model for the system is chosen which
can be any of the generic models. Development takes
place.
Planning
The project is reviewed and the next phase of the spiral
is planned.
In what situations in the spiral model used?
Spiral model has been very influential in helping people think about iteration in software processes and
introducing the risk-driven approach to development
In practice, however, the model is rarely used as
published for practical software development
Describe the V-Shaped Model
A variant of the Waterfall that emphasizes the
verification and validation of the product.
Testing of the product is planned in parallel with a
corresponding phase of development.
Illustrate the v-shaped model
*See notes for illustration and explanations of the steps
What are the strengths of the V-Shaped model
Emphasize planning for verification and validation of the product in early stages of product development
Each deliverable must be testable
Project management can track progress by milestones
Easy to use
What are the weaknesses of the V-Shaped model
Does not easily handle concurrent events
Does not handle iterations or phases
Does not easily handle dynamic changes in requirements
Does not contain risk analysis activities
When is the V-Shaped Model used?
Excellent choice for systems requiring high reliability eg hospital patient control applications
All requirements are known up-front
When it can be modified to handle changing requirements beyond analysis phase
Solution and technology are known.
What are the disadvantages of Heavy-Weight models in general
Delivered late,
Over budget,
Failure to meet functional and non-functional requirements,
Not responsive to change,
Poor assessment of risk,
Discovery of major problems late
