Software development typically aims to align specifications with implementation.
For this reason, we design the software to meet the specifications, and then implement it based on that design. We then use tests to confirm that the implementation fulfills the specifications, correcting the implementation if there are discrepancies, or clarifying the specifications if they are ambiguous.
This can be called specifications-and-implementation-based engineering.
In contrast, when discussing software today, user experience is becoming increasingly important.
Furthermore, it is the behavior of the software, not its implementation, that actually shapes the user experience.
Therefore, outside the framework of specifications and implementation, experience and behavior exist.
Consequently, I believe it is worth exploring the concept of Experience & Behavior Engineering, which is based on experience and behavior.
Liquidware
Experience & Behavior Engineering is an unrealistic approach with traditional software development methods.
This is because it requires improving the user experience without strict boundaries or functional divisions in the specifications. A casual request from a user to improve their experience might even necessitate discarding all previously developed software.
On the other hand, if a time comes when agent-based software development automation using generative AI becomes commonplace, rebuilding entire software systems will be acceptable.
Furthermore, in such an era, by equipping released software with an AI engineer chatbot, it is conceivable that we will enter an age of "liquidware," where the UI can be modified to suit each user's preferences.
Liquidware means something more flexible than traditional software, perfectly fitting each individual user.
When this era of automated development and liquidware arrives, the engineering paradigm of specifications and implementation will become outdated.
Instead, we will transition to a paradigm of Experience & Behavior Engineering.
What is Behavior?
Simply put, behavior is a state that changes over time.
And to test behavior is nothing less than to test this time-varying state.
Furthermore, testing behavior is not about confirming alignment with a specification that defines how states transition. Instead, behavior is tested based on the quality of the user's experience.
Of course, if there are bugs that cause the system to perform unintended operations by the user or developer, these also significantly impair the user experience. Therefore, behavior testing includes verifying functional conformity and functional validity.
After meeting these basic functional requirements, the focus shifts to testing for high-quality behavior from the perspective of user experience.
The Ultimate Experience
For humans, the ultimate user experience is the control of one's body when in good health.
Consider this: every day, we control a complex, yet highly constrained and limited body weighing tens of kilograms, using it for purposeful activities.
If one were to attempt to control such a heavy, complex, and highly constrained system to perform desired activities, the experience would typically be quite poor.
However, as long as we are not feeling unwell, we move this heavy, complex, and highly constrained body as if it were weightless, manipulate it as effortlessly as a simple mechanism, and pay no mind to its limitations and constraints as if they didn't exist.
This is the ultimate experience.
By pursuing high-quality behavior, it may become possible to provide an experience on par with controlling one's own body.
In other words, even if a system is slow to process, complex in functionality, and has many limitations and constraints, a completely stress-free liquidware experience could be realized.
In Conclusion
Ultimate liquidware will offer an experience akin to that of our own bodies.
Such liquidware will become something like a body to us.
Every time ultimate liquidware proliferates or its functions are enhanced, it will feel as if our own bodies are being extended.