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   Operational Requirements for Extension and Evolution of an Information S

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  • To: <xml-dev@lists.xml.org>
  • Subject: Operational Requirements for Extension and Evolution of an Information System
  • From: "Roger L. Costello" <costello@mitre.org>
  • Date: Thu, 3 Jun 2004 13:50:13 -0400
  • Importance: Normal

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 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  


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