# Where are special system words like MISSING listed (and what they do)?
**URL:** https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331
**Category:** Support
**Created:** [June 22, 2023, 5:11am UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331 "2023-06-22T05:11:14Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@dec](https://community.mp3tag.de/u/dec)
#### Post date: [June 22, 2023, 5:11am UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/1 "2023-06-22T05:11:14Z")
some time ago, i saw a very brief mention and use somewhere of a system word 'MISSING', and since then somewhere else i saw some mention of apparently other system words - NOT, MATCH, HAS, IS, AND (i didn't see any OR mentioned, although logically you would think it would be there)
so ARE these system words/functions?
if so, where would they be listed?
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### Author:  [@poster](https://community.mp3tag.de/u/poster)
#### Post date: [June 22, 2023, 5:14am UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/2 "2023-06-22T05:14:54Z")
> **[Filter and Search – Mp3tag Documentation](https://docs.mp3tag.de/filter/)**
>
> Documentation on Filter and Search and keywords to form complex filter expressions. Mp3tag is the universal Tag Editor.
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### Author:  [@dec](https://community.mp3tag.de/u/dec)
#### Post date: [June 22, 2023, 10:27am UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/3 "2023-06-22T10:27:25Z")
ok. i see this.
now if the Manual had a SEARCH, i could found this regardless of what strange place they put these.
i mean, under 'FILTERS'????
give me a break. 🙂
and these system functions/variables (reserved words) would have probably been quite useful to me previously ☹ when i was struggling to both come to grips with MP3Tag and with my untamed and messy data
thanks.
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### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [June 22, 2023, 10:37am UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/4 "2023-06-22T10:37:44Z")
> [@dec](#):
>
> i mean, under 'FILTERS'????
Yes, just as has been revealed to you in your own thread:
> [@Logical Operators ... Blank etc](https://community.mp3tag.de/t/logical-operators-blank-etc/60843):
>
> i can't find any operators for things like ifblank, ifchar, ifnumeric, and such so, for example, how do i test for a blank tag field? this is obviously a very useful/important test
And these keywords only work in filters not application-wide.
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### Author:  [@MotleyG](https://community.mp3tag.de/u/MotleyG)
#### Post date: [June 22, 2023, 11:23am UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/5 "2023-06-22T11:23:26Z")
> [@dec](#):
>
> i mean, under 'FILTERS'????
Operators _only_ work in the filter, so that is exactly where they should be.
> [@dec](#):
>
> and these system functions/variables (reserved words) would have probably been quite useful to me previously ☹ when i was struggling to both come to grips with MP3Tag and with my untamed and messy data
You are here for this reason. The existing data in your tags was poorly, or at least not consistently, maintained in the past. This is the same reason every other user has landed at mp3tag. It is free for Windows users, and a modest price for native Mac users. But the time saved using it is invaluable. Most seem to appreciate what mp3tag has to offer, a few can’t seem to grasp how it works and blame the universe.
Perhaps you are expecting far too much from the program, or the other users that have generously responded to your rampant requests to provide you guidance on correcting your own data. I have personally tried to reply where I could add support for you, but I can’t believe how ignorant most of your replies have been when you couldn’t get the desired results.
I’m sorry, but my time is valuable to me. I won’t be replying any further to your comments here.
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### Author:  [@dec](https://community.mp3tag.de/u/dec)
#### Post date: [June 22, 2023, 12:03pm UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/6 "2023-06-22T12:03:08Z")
"can't believe how ignorant most of your replies have been ..."
really??? really??
when i am struggling with a new complex program, and technolgy, and where the Manual does not have an essential Search function - that would have saved/save us ALL of a lot of time!
or virtually no examples that would have saved/save us all far more time.
and avoided the need for so many Support questions
yet it is somehow MY fault when i ask question while i am try to learn an understand????
AND, contrary to the ill-informed criticism i have got, when i am using MP34Tag, i usually have about EIGHT tabs open for different parts of Manual!
and btw, just HOW have ANY of my replies to you been anything but friendly and courteous???? pls name a single ONE.
talk about 'shoot the messenger'.
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### Author:  [@dec](https://community.mp3tag.de/u/dec)
#### Post date: [June 22, 2023, 12:21pm UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/7 "2023-06-22T12:21:56Z")
ahhh. do these only work as FILE foliters, because i have an Action that replaces (populates) a Field? something like %artist MISSING ....
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### Author:  [@ohrenkino](https://community.mp3tag.de/u/ohrenkino)
#### Post date: [June 22, 2023, 1:21pm UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/8 "2023-06-22T13:21:37Z")
> [@dec](#):
>
> do these only work as FILE foliters
Don't most manipulations in MP3tag effect files?
> [@dec](#):
>
> because i have an Action that replaces (populates) a Field?
Please show us the action. Or even better - as this seems to be a new probem: open a new thread.
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [June 23, 2023, 9:37am UTC](https://community.mp3tag.de/t/where-are-special-system-words-like-missing-listed-and-what-they-do/61331/9 "2023-06-23T09:37:33Z")