Lecture Software process improvement: Lesson 6 - Dr. Ghulam Ahmad Farrukh
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ETVX: Process Modeling
Technique
Lecture # 6
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Critical Software Process Issues
• Quality
• Product technology
• Requirements instability
– Unknown requirements
– Unstable requirements
– Misunderstood requirements
• Complexity
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Critical Software Process Issues
• Organizations that face the issues of quality,
product technology, requirements stability,
and/or complexity need to define ways to
address them
• A process architecture permits these
organizations to represent and manipulate
the process at the U level and then
selectively to refine it to the W and A level
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Process Framework
• The universal, worldly, and atomic levels of
process models can be presented in the
process framework – in other words
• Thus, the framework would give
established policies, procedures and
standards
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Process Framework
• The architectural framework of a process
helps in providing a definition for
• basic elements
• how they interact
• how they are decomposed into increasing
level of detail
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A Unit Cell
• The basic element of the process
architecture is the unit cell
• Each cell is defined to accomplish a
specified task and is uniquely identified
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A Unit Cell
Input
Output
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Detailed description of Unit Cell
Input
Entry
Task
Out
Exit
Output
In
Feedback
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Entry Conditions of a Unit Cell
• Each cell has required entry conditions
specified for task initiation that include the
inputs (one or more with their sources)
• Task standards, procedures, methods,
responsibilities, and required measures are
also defined
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Exit Conditions of a Unit Cell
• Exit conditions define the results produced,
their level of validation, and any posttask
conditions
• Cell feedback refers to any data provided to
or received from other stages in the process
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Basic Unit Cell Specification
Specification
Activities
Entry
Conditions to be met before task
initiation
Exit
Results produced
Feedback
In: Feedback from other stages
Out: Feedback to other stages
Task
What is to be done (by whom, how,
and when, including standards,
procedures, and responsibilities
Measurements
Task (activities, resources, time),
output (number, size, quality), and
feedback (number, size, quality)
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measures
ETVX
• ETVX as a modeling language
• Introduced by IBM in 1980
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Objectives of ETVX
• The objective of ETVX is to illustrate the
effective process performance
• It can be applied to as low a level as
required to control process
• A model developed in ETVX is expressed
as a set of interconnected activities each of
which has four sets of attributes
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ETVX Representation
•
•
•
•
Entry (E)
Task (T)
Verification (V)
Exit (X)
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Entry
• The Entry section defines the entry criteria
that must be satisfied for the process to be
initiated, and list the work products that
must be available as inputs to the process
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Tasks
• The Task section defines work to be carried
in performing the process. The order of the
task is generally, but not strictly sequential.
Some tasks may be concurrent with other
tasks
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Verification
• The verification section defines steps for
verifying that the process has been properly
executed, and that the associated work
products meet project objectives
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Exit
• The Exit section defines the exit criteria that
must be satisfied for the process to be
terminated. The exit criteria usually define
completion and verification work products,
in terms of qualitative aspects of the
products
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ETVX model
• An ETVX model indicates the relationship and
flow among the four aspects of an activity and
between activities
• The notion of formal entry, exit, and criteria go
back to the evolution of the waterfall development
process
• The idea is that every process step, inspection,
function test, or software design has a precise
entry and exit criteria
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Characteristics of ETVX
• ETVX is a taskbased model
• Each task must be explicitly defined
• The basic cells can be combined to create
process
• "bottomup" approach (A level to W and U
levels)
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An Example of ETVX
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Example of ETVX
• The generic activities of different process
models from the Ulevel’s perspective can
be listed as “design”, “implementation”,
and “test”
• When these activities are broken into more
detail, however, significant differences
show up.
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Example of ETVX
• Even with all these variations at the W
level, however, many software activities
can relatively standardized across different
projects
• It is thus possible to establish some basic
process cells that can be interconnected in
different ways to meet projectunique needs
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Example of ETVX
• The detailed structures of these standard
cells are then further defined by Alevel
models as needed
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Example of ETVX
• Let’s look at the “design”,
“implementation”, and “test” activities in
any process model using the ETVX
technique
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