In Object-Oriented programming, used to describe the knowledge of one programmatic Entity of the existance of another such Entity. An entity only knows of another entity if it acquires services from that entity. For instance, a report-generating component would know of a Database component so it can use it to read and write the data that it uses to generate those reports. This means that the Database component is visible to the report-generating component.

An entity (A) that knows of another entity (B) is by definition dependent on it. This is of great significance because entity (A) cannot be reused in a different software environment without entity (B) being available, and changes in entity (B) may require changes in entity (A). For example: changing the Database component so that extra-information has to be supplied when data is read or written requires that the report-generating entity be changed to supply this extra information.

As a general rule, the fewer visibilities there are in a software system, the easier it is to maintain and reuse.

... and winter driving

In places that get significant snowfall, visibility is an important consideration when travelling any significant distance. Here are some phrases you'll hear on the radio's travel forecasts:

Good Visibility

It's barely snowing, or not snowing at all. You can see more than 800 metres, or right to the horizon.

Reduced Visibility

You can see fairly well, but less than 800 metres. Reduced speed is wise.

Poor Visibility

Visibility is less than 500 metres. Reduced speed is essential. Typically there will be poor road conditions as well, compounding the risk to travel.

Large vehicles such as transport trucks may be able to see more from their higher vantage point. This won't help you at all, so don't try to emulate them as they breeze along.

Zero Visibility

Visibility is less than 200 metres, likely as little as 50 metres. You're not going to see something ahead of you before you hit it. Don't travel, or if you're already in transit, pull over as soon as it is safe to do so.

Snowploughs and other maintenance equipment will not work on the roads until visibility improves, so it's only going to get worse as time goes on.


This means it's snowing heavily and very windy. The combination can make it impossible to see your own hood ornament. You can get lost crossing the street. You don't want to be in control of a two ton motor vehicle in this situation.

Other factors

Make sure the car's windshield washer fluid is topped up before you leave, and every time you stop. Every damn time! You're likely to be spraying the stuff onto your windshield several times a minute. It would not do to run out.

Vis`i*bil"i*ty (?), n. [L. visibilitas: cf. F. visibilit'e.]

The quality or state of being visible.


© Webster 1913.

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