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To be effective, specs must be written clearly and consistently, using precise and succinct language.

To facilitate those goals, it is suggested that spec editors adhere to the style guidelines set forth in this document.


Use standard American English spelling, unless otherwise stated below.
Continue the history of the Web and use 'en-US' spelling for your specs and the technologies they document. Consult Wikipedia's Manual of Style for spelling for assistance.
Use "acknowledgements" instead of "acknowledgments".
Whenever 'dg' represents the "soft" /d͡ʒ/ sound, it should be followed by an 'e' or an 'i', to ensure it is not confused with the "hard" /dɡ/ sounds.
Use "cannot" when something is impossible or prohibited.
"Can not" implies a choice; "cannot" prevents one.


Use the Oxford comma.
When conjoining three or more items, place a comma between the second-to-last item and the conjunction.
Use double quotation marks for outer quotes and single quotation marks for inner quotes.
This is slowly becoming the worldwide standard anyway, but just in case you need to be reminded.
Where applicable, use double quotation marks for quoted terms or scare quotes and single quotation marks for literal sequences of characters.
You could use double quotation marks for the latter, but single ones are less bulky. Besides, it's better to use semantic markup and/or styling to get the message across anyway.
Only include between quotation marks what is actually being quoted.
It's OK to have punctuation on the outside of a quotation mark. It's even OK to have punctuation on both sides of a quotation mark, if that's how things turn out.
Avoid parenthesizing an entire sentence within another sentence.
It's OK to let a parenthetical sentence stand on its own.
Include trailing punctuation within parentheses.
You should be able to remove a parenthetical without breaking anything around it; if you have trailing punctuation outside parentheses, removing the parenthetical will leave the punctuation orphaned.


Bags of bits

Be careful with your use of the terms "file" and "resource".
Make sure your definitions refer only to bags of bits, and not also to stuff in the Real World™ (like baskets of apples).

Collections of values

For a keyless collection of values, use the provided term when … and …
uniqueness doesn't matter uniqueness matters
order doesn't matter "unordered list" "set"
order matters "list" "ordered set"
For a keyed collection of values, use the provided term when there can be … and …
only one key per value more than one key per value
only one value per key "bidirectional map" "map"
more than one value per key "inverse map" "multimap"
Use "object" for a map whose values can be functions.
This helps to distinguish cases where values might not be static data types.
Do not use "dictionary" for any collection of values.
There is potential for confusion between a map (which, as mentioned above, can have only one value per key) and a Real World™ dictionary (which can have more than one definition per headword).

Willful violations of other specs

When willfully and deliberately violating standards set out in other documents, use the term "willful violation" instead of simply "violation".
"Violation" makes you sound naughty; "willful violation" makes you sound knowledgeable.
When willfully and deliberately violating standards set out in other documents, carefully document the differences from the standards in question, as well as the rationale for each decision to differ.
If you don't explain your decision making, there will be no incentive to follow your standard over the existing one.


Use the form "X is Y" when defining a term.
A definition asserts that the relationship between X and Y exists and is one of absolute equality.
"A baz is a foo that bars."
X === Y
Use the form "X is Y" or "X is equal to Y" when comparing for equality.
A conditional questions whether the relationship between X and Y is one of equality.
"If baz is equal to foo, then bar."
X == Y
Use the form "set X to Y" when assigning a value.
Make all assignments explicit and unambiguous.
"Set foo to 'bar'."
X = Y