BoxObject and CellObject (3) 

Create a BoxObject and CellObject:

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Both exist:

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Both can be deleted with NotebookDelete:

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ChannelObject (2) 

Using ChannelObject does not actually create a channel:

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Using CreateChannel makes the channel live:

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CloudObject (2) 

Using CloudObject does not actually create a cloud object:

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Using CloudPut or similar functions creates the object:

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Databin (1) 

Check if a Databin exists:

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DatabaseReference (1) 

A DatabaseReference exists if it is backed by a file that exists or if it is connected:

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ExternalSessionObject (3) 

External sessions exist while they are active:

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Use DeleteObject to end the session:

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Now, the session no longer exists:

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File (1) 

For a File, ObjectExistsQ is equivalent to FileExistsQ:

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LocalObject (2) 

For a LocalObject, ObjectExistsQ is equivalent to FileExistsQ:

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Use Put to create the local object:

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NotebookObject (2) 

A NotebookObject exists only if the window has not been closed:

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Closing the window destroys the NotebookObject:

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PermissionsGroup (3) 

Check if a PermissionsGroup exists:

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Create the group with CreatePermissionsGroup:

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Now it exists:

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PersistentObject (3) 

Using PersistentObject does not actually create a persistent object:

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Assign a value to create the object:

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Now it exists:

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ResourceFunction (2) 

Check if a ResourceFunction exists:

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Delete the resource:

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Functions published in the Wolfram Function Repository always exist:

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ResourceObject (1) 

Check if a ResourceObject exists:

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SearchIndexObject (2) 

Check if a SearchIndexObject exists:

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Delete the index:

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TaskObject (2) 

A task only exists until it is complete:

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Once completed, it no longer exists:

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URL (1) 

See if a URL exists:

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Streams (2) 

Test if an InputStream or OutputStream is open:

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Close the stream:

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Strings (1) 

Strings are either interpreted as URLs or files:

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