Title: Message




Hi Folk,
 
Here is my 
attempt at summarizing some of yesterday's discussions.
 
Operational 
Environment
 
The information 
system lives in an environment where change is the only constant.  The 
world is changing, the users are changing.  The system must be capable of 
changing in unexpected ways.
 
Operational 
Requirements
 
The information system must be designed in such a 
way that it is capable of dynamically "growing" 
and "changing" through user interactions.   That 
is:
 
- the 
system must be capable of growing to support "more of" an existing 
capability.  I refer to this capability as "system extensibility".  

 
- the 
system must be capable of changing to support capabilities that were never 
imagined by the system designers.  I refer to this capability as "system 
evolvability.  
 
Once 
the initial system is launched, the system 
designers and developers are out of a job!  The system grows and changes on its 
own, as a result of interactions with the users.  
 
Example of Extending an Information 
System:
 
Suppose that the system development team has implemented a keyword search 
capability.  Further, the team 
has provided a mechanism for users to add additional keywords (and map them to 
the system's data).  The keyword 
search capability already exists.  It was designed and implemented a 
priori.  The users are simply 
extending an existing capability.
 
Example of Evolving an Information 
System:
 
Suppose that the system development team has 
NOT implemented a capability to 
search based upon category.  Suppose that some time after the system has 
been in operation the users realize the need for category-based searching.  Let's suppose that the team has provided a generic mechanism which allows the users to create mappings to the system data.  The users employ 
this mechanism to create the category-based search 
capability.  This new capability 
was never conceived by the system developers.  Thus, the system has 
evolved (in an unexpected way).
 

[Len, help me 
here] New systems may spawn off from the original information 
system...
 
Comments?  
/Roger