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Software Engineering – The Software Process

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					             Software Engineering – The Software Process
PRESCRIPTIVE MODELS

Every software engineering organization should describe a unique set of framework
activities for the software process(es) it adopts.

It should populate each framework activity with a set of software engineering actions,
and define ach action in terms of a task set that identifies the work (and work
products) to be accomplished to meet the development goals.

It should then ADAPT the resultant process model to accommodate the specific nature
of each project, the people who will do the work, the environment.

Regardless of the model, all models contain the following components:

u   communication
u   planning
u   modeling
u   construction
u   deployment

Which of these phases do you think is most difficult and in what situations?
            Software Engineering – The Software Process
PROCESS MODELS

What do you think the most popular process model is?

Waterfall
Incremental
Evolutionary
Component Based
Formal
             Software Engineering – The Software Process
PROCESS MODELS

What do you think the most popular process model is?

I would say that the “no process model” is the most popular.
             Software Engineering – The Software Process
PROCESS MODELS – WATERFALL

The “Classic Life Cycle”, The “Textbook Cycle”

A systematic, sequential approach with the following steps:
u Customer Specification of Requirements (Communication)
u Planning (Estimating, Scheduling, Tracking)
u Modeling (Analysis and Design)
u Construction (Code and Test)
u Deployment (Delivery, Support, and Feedback)

The book calls the first phase communication. I do not like this definition as
communication must occur at all stages.
              Software Engineering – The Software Process
PROCESS MODELS – WATERFALL

When is the waterfall process model appropriate?

In a purest sense, probably never. I have never worked on a project that follows a
completely linear progression.

However, the waterfall process is appropriate if followed in spirit if not the letter of the
model in some situations:

u   Well defined projects
u   Projects with no technology risks
u   Well defined domains
u   Stable requirements
              Software Engineering – The Software Process
PROCESS MODELS – WATERFALL

Why is it difficult to follow?

u Hard to follow a strictly sequential path.
u Customers have difficulty stating ALL the requirements explicitly
u Customers business model changes during the course of developing the application
u Customers are required to have patience, since a working program is not available
until very late in the process.
             Software Engineering – The Software Process
PROCESS MODELS – INCREMENTAL PROCESS MODEL

Even with well defined projects, a linear approach is often difficult.

Additionally, sometimes a portion of the software needs to be delivered early.

The incremental model combines elements of the waterfall model applied in an
iterative fashion.

Incremental model delivers an operational product with each increment.

Works well for project resource management (staffing).
          Software Engineering – The Software Process
PROCESS MODELS – INCREMENTAL PROCESS MODEL
             Software Engineering – The Software Process
PROCESS MODELS – RAD MODEL

RAPID APPLICATION DEVELOPMENT (RAD)

Incremental software process that emphasizes a short development cycle.

Highly efficient waterfall model in which rapid development is achieved by using
component based construction.

Requires well understood project scope.

Same framework as waterfall:
u Customer Specification of Requirements (Communication)
u Planning (Estimating, Scheduling, Tracking)
u Modeling (Analysis and Design)
u Construction (Code and Test)
u Deployment (Integration, Delivery, Support, and Feedback

Key difference is parallel development during Modeling and Construction.
Also added to Deployment is an INTEGRATION phase.
          Software Engineering – The Software Process
PROCESS MODELS – RAD MODEL
           Software Engineering – The Software Process
PROCESS MODELS – RAD MODEL

Usual development time is less than three months.

Drawbacks:
u Large scalable projects, requires sufficient human resources
u Everyone must buy in to short term delivery
u Some systems can not be modularized easily
u Difficult when there are high technology risks

u Integration Risk (Not in the book, to me this is the largest concern.)
            Software Engineering – The Software Process
PROCESS MODELS – EVOLUTIONARY PROCESS MODEL - PROTOTYPING

Customers define general objectives , but does not identify the details.

Often, the customer doesn’t know what they want the system to look like.

Can be a stand alone process or integrated into other models.

I prefer it to be integrated.

A repeating cycle of the following steps include:
u Communication
u Quick Plan
u Modeling Quick Design
u Construction of Prototype
u Deployment & Feedback
           Software Engineering – The Software Process
PROCESS MODELS – EVOLUTIONARY PROCESS MODEL - PROTOTYPING

Depending upon the complexity I recommend a first pass with “Paper
Prototypes”.

“Paper” can be virtual with mockups of the application being developed in
either a development environment like Visual Studio or even HTML.

Second pass could be a semi functional application with no data connectivity.

Third pass for the developers to try any unknown technical issues.

Often good for these prototypes to be used for requirements gathering and
to reduce technology risks. Best if the prototype is a throw-away. One good
reason to develop your prototype in a different language/system than the
final project
             Software Engineering – The Software Process
PROCESS MODELS – EVOLUTIONARY PROCESS MODEL - PROTOTYPING

Drawbacks:

u Customers like the prototype and want to place it in production.
u Developers forget the design decisions and their mistakes leak into the
production system.
            Software Engineering – The Software Process
PROCESS MODELS – EVOLUTIONARY PROCESS MODEL – SPRIAL MODEL

An evolutionary software model that couples the iterative nature of
prototyping with the controlled and systematic aspects of the waterfall model.

This is true, but with one addition: risk analysis.

At each cycle through the spiral, milestones are achieved and risk is
reevaluated.
         Software Engineering – The Software Process
PROCESS MODELS – EVOLUTIONARY PROCESS MODEL – SPRIAL MODEL
           Software Engineering – The Software Process
PROCESS MODELS – EVOLUTIONARY PROCESS MODEL

Most developers lean towards evolutionary process models.

They have inherent problems:

u Prototyping and similar evolutionary models are hard to plan, thus hard to
estimate, thus hard to contract. How many cycles will there be?
u Speed of evolution is difficult to dictate
u Software processes should be focused on flexibility and extensibility rather
than on high quality.

Is the third statement true? Why is this a goal?
            Software Engineering – The Software Process
PROCESS MODELS – EVOLUTIONARY PROCESS MODEL

Most developers lean towards evolutionary process models.

They have inherent problems:

u Prototyping and similar evolutionary models are hard to plan, thus hard to
estimate, thus hard to contract. How many cycles will there be?
u Speed of evolution is difficult to dictate
u Software processes should be focused on flexibility and extensibility rather
than on high quality.

Is the third statement true? Why is this a goal?

The concept behind it is that if software is late, the opportunity of it is lost.
           Software Engineering – The Software Process
PROCESS MODELS – SPECIALIZED PROCESS MODEL
COMPONENT-BASED DEVELOPMENT

Commercial off-the-shelf software components, can be used when software
is built.

Process includes:
u Identification of candidate components
u Either object-oriented or procedural
u Consider integration issues
u Design a software architecture
u Integrate components
u Comprehensive testing

Does anyone do this as a pure process model? More likely as part of another
model.

We all use pre-built components. i.e. Borland text editor, advanced data grid,
Date/Time pickers, etc
           Software Engineering – The Software Process
PROCESS MODELS – SPECIALIZED PROCESS MODEL
FORMAL METHODS MODEL

The Formal Methods Model encompasses a set of activities that leads to
formal mathematical specification of computer software.

In theory, the following is reduced when using formal methods:
u Ambiguity
u Incompleteness
u Inconsistency

Do you agree?
             Software Engineering – The Software Process
PROCESS MODELS – SPECIALIZED PROCESS MODEL
FORMAL METHODS MODEL

Drawbacks:

u The development of formal models is currently quite time consuming and
expensive
u Few software developers have the background, thus extensive training is
required. (is training viable? COBOL -> OOP)
u Difficult to use formal model to communicate with a non-technical
customer.
u Forest and Trees.

Useful for safety critical application or anywhere failure is highly costly.

				
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posted:10/9/2013
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