> For the complete documentation index, see [llms.txt](https://docs.wem.io/platform/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.wem.io/platform/wemreference/functions/validation/isknown.md).

# IsKnown

{% hint style="info" %}
The **`IsKnown()`** function checks whether the input parameter is known and recognizable as a value or element. 

It is only <mark style="color:orange;">slightly different</mark> from [`HasValue()`](/platform/wemreference/functions/validation/hasvalue.md) in the way that an empty text-value is a known element (it is a text),  but it does not have a value.&#x20;

This function is SQL compatible. For more information about SQL compatibility, see our [documentation](/platform/wemreference/sql-compatibility.md).
{% endhint %}

{% hint style="danger" %}
**We advise to use the** [**HasValue()**](/platform/wemreference/functions/validation/hasvalue.md) **and** [**IsEmpty()**](/platform/wemreference/functions/validation/isempty.md) **functions as they are more practical and logical in use.**
{% endhint %}

{% hint style="warning" %}
If the input parameter is a list or a collection (like a Concept-Set), then the `IsKnown()` function checks if the list has at least 1 row.

The[ `IsUnknown()` ](/platform/wemreference/functions/validation/isunknown.md)function checks the opposite of this function.
{% endhint %}

{% hint style="success" %}
Returns <mark style="color:green;">`true`</mark> if <mark style="color:blue;">`parameter`</mark> is not unknown.\
Returns <mark style="color:red;">`false`</mark> if <mark style="color:blue;">`parameter`</mark> is unknown.&#x20;
{% endhint %}

### Syntax

<details>

<summary><code>IsKnown(</code><mark style="color:blue;"><code>parameter</code></mark><code>)</code></summary>

`IsKnown( "1" )`\
*=> True*

`IsKnown(`*`unknownnumber`*`)`\
*=> False*

`IsKnown( "" )`\
*=> True >> <mark style="color:orange;">This is different from HasValue( "" ) : "" is a known element (an empty string) but it does not have a value according to the HasValue implementation</mark>.*

`IsKnown( "` `" )`\
*=> True*

`IsKnown( '' )`\
*=> True*

`IsKnown( {} )`\
*=> False*

`IsKnown( [List WithRows] )`\
*=> True*

`IsKnown( [List WithNoRows] )`\
*=> False*

`IsKnown(ToString(`*`unknownstring`*`))`\
*=> **TRUE** > <mark style="color:orange;">the ToString on UnknownString makes the element Known as a String Type but with an Empty Value >> better use the HasValue or IsEmpty functions for more practical and logical use</mark>*

</details>

### Parameters

<table><thead><tr><th width="150">Name</th><th width="150">Type</th><th width="150" align="center">Required</th><th width="284.6178790534619">Description</th><th data-hidden>Required?</th></tr></thead><tbody><tr><td><mark style="color:blue;">parameter</mark></td><td>any</td><td align="center"><span data-gb-custom-inline data-tag="emoji" data-code="2611">☑️</span></td><td>Field that is checked for a value </td><td>yes</td></tr></tbody></table>


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