How can I allow parameter sets to be optional? :)

parameter-issue.ps1

function Install-File {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory=$true, Position=0)][string]$Path,
        [Parameter(ParameterSetName='SourcePath')][string]$SourcePath,
        [Parameter(ParameterSetName='Content')][string]$Content,
        [Parameter(ParameterSetName='DownloadUrl')][string]$DownloadUrl
    )

    # ...
}

# Valid inputs
Install-File -Path C:\myfile.txt  # QUESTION: How can I allow this scenario to be accepted?
Install-File -Path C:\myfile.txt -SourcePath C:\source.txt
Install-File -Path C:\myfile.txt -Content hello
Install-File -Path C:\myfile.txt -DownloadUrl http://myfile.txt

function Install-File {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory=$true, Position=0,ParameterSetName='Default')]
        [Parameter(Mandatory=$true, Position=0,ParameterSetName='SourcePath')]
        [Parameter(Mandatory=$true, Position=0,ParameterSetName='Content')]
        [Parameter(Mandatory=$true, Position=0,ParameterSetName='DownloadUrl')]
        [string]$Path,
        [Parameter(ParameterSetName='SourcePath')]
        [string]$SourcePath,
        [Parameter(ParameterSetName='Content')]
        [string]$Content,
        [Parameter(ParameterSetName='DownloadUrl')]
        [string]$DownloadUrl
    )

    # ...\
    if($sourcePath)
    {
        write-host 'SourcePath'
    }elseIf($content)
    {
        write-host 'Content'
    }elseIf($DownloadUrl)
    {
        write-host 'DownloadUrlCode'
    }else{
        write-host 'Use something else'
    }

}

# Valid inputs
Install-File -Path C:\myfile.txt  # QUESTION: How can I allow this scenario to be accepted?
Install-File -Path C:\myfile.txt -SourcePath C:\source.txt
Install-File -Path C:\myfile.txt -Content hello
Install-File -Path C:\myfile.txt -DownloadUrl http://myfile.txt