Is there a guideline on writing message that are shown to users of an app?

Question

Is there any guideline on writing message which are shown to the user of an app using toast?

For example, if an error occurred, should the app display

Failed writing to the file

or

Failed writing to the file.

Should sentences use full stop? I don't see full stops used in some language REPLs when there is only one sentence. Is there any standard way?

Answer 1

I recognize a general industry-wide problem. As long as I have been in interactive software development I have encountered cringing language. I can always tell it is bad, I can always make it better (and I usually do), but I have no cookbook to do this. It would be great to have a standard rule set that everyone (especially those who do not see the problem) can apply. This is an issue for UI messages and logging alike.

What I have seen:

• Incomplete sentences, lazy staccato style.
• Use of exclamation marks for no reason.
• Use of all capitals for no reason.
• Useless information on a level meaningless to the user.
• Active/personal form instead of passive form ("Cannot write to file" instead of "The file could not be written.").
• Frills like lots of dots at the end or dashes over and under.

To a user it often feels rude or indifferent. I have seen UI guidelines but little on language.

I recognize this has been more an elaboration of the question than an answer so far. Here's what I usually try to apply.

• Use full yet brief sentences.
• Be polite.
• Be considerate of the message level (info, warning, error).
• Use passive form (the system is not a person).
• Provide only meaningful information. If you want to show an exception message, introduce it, like "An exception occurred:".
• Do not present puzzles, make it clear what is expected if the user needs to do something (different).

Answer 2

Captions, titles, menu items and such should not end in a full-stop.

So if Failed writing to the file is a dialog title, that is okay.

For content, a message a full stop is often missing, if the text contains just one sentence. This is not correct. In one case even I fail (colon style):

Failed writing to the file: C:\Temp\interesting_news.pdf

I use this style a bit too often, as real comma like quotes are cumbersome.

My rule: more than one sentence, or a long sentence should end with a period.

The same flexibility holds for (bullet) lists

         Xyz:      Xyz:      Xyz.
∙ aaa    ∙ aaa;    ∙ aaa,    ∙ Aaa.
∙ bbb    ∙ bbb;    ∙ bbb,    ∙ Bbb.
∙ ccc    ∙ ccc.    ∙ ccc.    ∙ Ccc.

Without period for captions, like on slides.