Computer and Machine Vision - Computational Software Techniques in Engineering

You can't physically touch software. You can hold a floppy disk or CD-ROM in your hand, but the software itself is a ghost that can be moved from one object to another with little difficulty. In contrast, a road is a solid object that has a definite size and shape. You can touch the the material and walk the route...
Software is a codification of a huge set of behaviors: if this occurs, then that should happen, and so on. We can visualize individual behaviors, but we have great difficulty visualizing large numbers of sequential and alternative behaviors...
The same things that make it hard to visualize software make it hard to draw blueprints of that software. A road plan can show the exact location, elevation, and dimensions of any part of the structure. The map corresponds to the structure, but it's not the same as the structure. Software, on the other hand, is just a codification of the behaviors that the programmers and users want to take place. The map is the same as the structure... This means that software can only be described accurately at the level of individual instructions... A map or a blueprint for a piece of software must greatly simplify the representation in order to be comprehensible. But by doing so, it becomes inaccurate and ultimately incorrect. This is an important realization: any architecture, design, or diagram we create for software is essentially inadequate. If we represent every detail, then we're merely duplicating the software in another form, and we're wasting our time and effort.

A machine, receiving at distant times and from many hands new combinations and improvements, and becoming at last of signal benefit to mankind, may be compared to a rivulet, swelled in its course by tributary streams until it rolls along a majestic river, enriching in its progress provinces and kingdoms.
In retracing the current, too, from where it mingles with the ocean, the pretensions of even ample subsidiary streams are merged in our admiration of the master-flood. But, as we continue to ascend, those waters which, nearer the sea, would have been disregarded as unimportant, begin to rival in magnitude, and divide our attention with, the parent stream; until, at length, on our approaching the fountains of the river, it appears trickling from the rock, or oozing from among the flowers of the valley. So, also, in developing the rise of a machine, a coarse instrument or a toy may be recognized as the germ of that production of mechanical genius whose power and usefulness have stimulated our curiosity to mark its changes and to trace its origin. The same feelings of reverential gratitude which attached holiness to the spots whence mighty rivers sprung, also clothed with divinity, and raised altars in honor of the saw, the plough, the potter's wheel, and the loom.

Vision is the Art of seeing Things invisible.