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2.5 Availability
02. Data Quality and Integrity
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2.5.02 Data Quality and Integrity:
Every effort must be taken to maintain a high degree of data quality so the data can be relied upon.
A drop down list of predefined values has a consistent data quality, while a text field is only suitable where data quality is not critical.
Text fields can be assigned as integer or decimal numbers only to improve data quality.
Telephone numbers and email addresses have a style that can be enforced by real-time validation.
Name and address field words can be capitalized to provide a more consistent quality of data.

Data Integrity Policy:
To operate the very best application service in the world demands best practice standards and policies that others are not good enough to emulate.
Data integrity policy defines precise and exacting rules for the permitted values of each and every field.   Low data quality is a constant cause of business failues and so by imposing very high data quality we are eliminating a cause of many business failues.
As data is entered, it must be subject to strict rules that define its permitted values - free format text is unsuitable for automatic process and so it has very low value.
As data is created it is also subject to exact rules that define its reasonableness - operational warnings are signalled where data values are not as expected.

Symbols Policy:
Symbols must be eliminated where ever possible.
An apostrophe is permitted in a persons name, but it not required in any other business data.
The use of currency symbols may be printed differently and will have alternative meanings is other countries - GBP and USD are recommended.
Unpredictable behaviour may evolve where data includes symbols that have different meaning to different computers.

Alternatives:
Apostrophe is replaced with a top hat symbol.
Ambersand is replaced with a at symbol.

  
Problem Symbols:
The top left key with Not, back-apostrophe and broken bar symbols must not be used - unique to UK.
The double quotation mark must not be used - reserved for CSV download to a spreadsheet.
The percent symbol must not be used - reserved for wild searches.
The star symbol must not be used - reserved for wild searches.
The vertical bar symbol must not be used - reserved for wild searches.
The pair of angle brackets may not be used - reserved for HTML.
The apostrophe symbol must not be used - reserved for field terminations - alternative is the top hat symbol.
The ambersand symbol must not be used - it will terminate parameter strings - alternative is the at symbol.

Permitted Symbols:
The pound and dollar symbols do not cause technical problems, but may be show differently in other countries, may not be printed and do not exist on all keyboards.
The hash symbol does not cause technical problems, but may be show differently in other countries, may not be printed and do not exist on all keyboards.
The question mark and exclamation mark do not cause problems and may be permitted.
The top hat does not cause problems and may be permitted - it is used to substitute for an apostrophe in a persons name.
The pair of curved brackets does not cause problems and may be permitted.
The pair of curly brackets does not cause problems and may be permitted.
The pair of square brackets does not cause problems and may be permitted.
The minus and plus symbols do not cause problems and may be permitted.
The underline and equals symbols do not cause problems and may be permitted.
The comma and period symbols do not cause problems and may be permitted.
The colon and semi-colon symbols do not cause problems and may be permitted.
The back slash and forward slash symbols do not cause problems and may be permitted.
The question mark and forward slash symbols do not cause problems and may be permitted.
The at symbol and tylde symbol do not cause problems and may be permitted, but these may be used as reserved symbols for other symbols.