What is a Good Information System?:

A good information system is one that has the information you want when and where you want it, in a form you want it. It should cost as little as possible, and in no case more than the information is worth, and it should protect the information and itself.

The Information You Want:

The information you want is sufficient and correct information. If you are making an appointment, you will need to know all conflicting appointments. You might also need to know if they require travel, since possible arrival times may be significant. So merely knowing that you had an appointment at a given time may not be sufficient. If you are buying a product or service, you will want its current price. A price list you have from a week past may be outdated.

When and Where you Want it:

The idea of information "where" you want it is really a corollary of the idea of having information "when" you want it. At the moment you want it, you will want it wherever you are. There are technological, administrative and political factors that make certain solutions appropriate in given situations. It is convenient to look at problems first by identifying the area in which the need for information is likely to occur. The area can then be classed as a "zone of mobility". The zones of mobility can be classed as

1. within a building,
2. within a city, and
3. inter city and world wide

Levels of Portability:

Levels of portability tend to be more a matter of personal preference than practical requirement. While one can generalize that the smaller and lighter a device is, the better for carrying, one must balance this against such factors as cost, display technology and durability.

In general it is convenient to class devices as:

1. Moveable (aka luggable, suitcase size)
2. carryable (briefcase or shoulderbag)
3. wearable (holster, coat pocket, pants pocket, shirt or vest pocket)