software

These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided
with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 1
Supplementary Slides for
Software Engineering:
A Practitioner's Approach, 6/e
Part 1
copyright © 1996, 2001, 2005
R.S. Pressman & Associates, Inc.
For University Use Only
May be reproduced ONLY for student use at the university level
when used in conjunction with Software Engineering: A Practitioner's Approach.
Any other reproduction or use is expressly prohibited.
This presentation, slides, or hardcopy may NOT be used for
short courses, industry seminars, or consulting purposes.

Software Engineering: A Practitioner’s Approach, 6/e
Chapter 1
Software and Software Engineering
copyright © 1996, 2001, 2005
R.S. Pressman & Associates, Inc.
For University Use Only
May be reproduced ONLY for student use at the university level
when used in conjunction with Software Engineering: A Practitioner's Approach.
Any other reproduction or use is expressly prohibited.

Software’s Dual Role
 Software is a product
 Delivers computing potential
 Produces, manages, acquires, modifies, displays, or transmits
information
 Software is a vehicle for delivering a product
 Supports or directly provides system functionality
 Controls other programs (e.g., an operating system)
 Effects communications (e.g., networking software)
 Helps build other software (e.g., software tools)

What is Software?
Software is a set of items or objects
that form a “configuration” that
includes
• programs
• documents
• data ...

What is Software?
 software is engineered
 software doesn’t wear out
 software is complex

Wear vs. Deterioration

Software Applications
 system software
 application software
 engineering/scientific software
 embedded software
 product-line software
 WebApps (Web applications)
 AI software

Software—New Categories
 Ubiquitous computing—wireless networks
 Netsourcing—the Web as a computing engine
 Open source—”free” source code open to the computing
community (a blessing, but also a potential curse!)
 Also … (see Chapter 32)
 Data mining
 Grid computing
 Cognitive machines
 Software for nanotechnologies

Legacy Software
 software must be adapted to meet the needs of new
computing environments or technology.
 software must be enhanced to implement new
business requirements.
 software must be extended to make it interoperable
with other more modern systems or databases.
 software must be re-architected to make it viable
within a network environment.
Why must it change?

Software Evolution
 The Law of Continuing Change (1974): E-type systems must be continually adapted else they
become progressively less satisfactory.
 The Law of Increasing Complexity (1974): As an E-type system evolves its complexity increases
unless work is done to maintain or reduce it.
 The Law of Self Regulation (1974): The E-type system evolution process is self-regulating with
distribution of product and process measures close to normal.
 The Law of Conservation of Organizational Stability (1980): The average effective global activity
rate in an evolving E-type system is invariant over product lifetime.
 The Law of Conservation of Familiarity (1980): As an E-type system evolves all associated with it,
developers, sales personnel, users, for example, must maintain mastery of its content and
behavior to achieve satisfactory evolution.
 The Law of Continuing Growth (1980): The functional content of E-type systems must be
continually increased to maintain user satisfaction over their lifetime.
 The Law of Declining Quality (1996): The quality of E-type systems will appear to be declining
unless they are rigorously maintained and adapted to operational environment changes.
 The Feedback System Law (1996): E-type evolution processes constitute multi-level, multi-loop,
multi-agent feedback systems and must be treated as such to achieve significant improvement
over any reasonable base.
Source: Lehman, M., et al, “Metrics and Laws of Software Evolution—The Nineties View,”
Proceedings of the 4th International Software Metrics Symposium (METRICS '97), IEEE, 1997, can be
downloaded from: http://www.ece.utexas.edu/~perry/work/papers/feast1.pdf

Software Myths
 Affect managers, customers (and other non-technical
stakeholders) and practitioners
 Are believable because they often have elements of
truth,
but …
 Invariably lead to bad decisions,
therefore …
 Insist on reality as you navigate your way through
software engineering

software

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