Lehman
has given eight laws for E-Type software evolution -
● Continuing
change - An E-type software system must continue to adapt to the real
world changes, else it becomes progressively less useful.
● Increasing
complexity - As an E-type software system evolves, its complexity tends to
increase unless work is done to maintain or reduce it.
● Conservation
of familiarity - The familiarity with the software or the
knowledge about how it was developed, why was it developed in that particular
manner etc. must be retained at any cost, to implement the changes in the
system.
● Continuing
growth- In order for an E-type system intended to resolve some business
problem, its size of implementing the changes grows according to the lifestyle
changes of the business.
● Reducing
quality - An E-type software system declines in quality unless rigorously
maintained and adapted to a changing operational environment.
● Feedback
systems- The E-type software systems constitute multi-loop, multi-level
feedback systems and must be treated as such to be successfully modified or
improved.
● Self-regulation
- E-type system evolution processes are self-regulating with the
distribution of product and process measures close to normal.
● Organizational
stability - The average effective global activity rate in an evolving E-type
system is invariant over the lifetime of the product.