Hello all,
sorry for bother you with issue both I think that I misunderstand how the mod_negotiation and mod_rewrite work is working.
In my apache I have enabled Virtual Host called:
<VirtualHost _default_:443>
SSLEngine on
DocumentRoot "/opt/apache/htdocs/ssldocs"
AddType text/html .shtml
RewriteEngine on
RewriteRule .* - [F]
RewriteMap unity txt:/opt/apache/conf/unity.map
RewriteRule ^/(common|public)/(.*)  /opt/unity/htdocs/$1/$2 [L]
RewriteRule ^/([^/]+)$              ${unity:$1|/$1} [L]
RewriteRule ^/([^/]+)/(.*)  ${unity:$1|/opt/apache/htdocs/ssldocs/$1}/$2 [L]
RewriteLog "/var/log/apache2/rewrite_log"
RewriteLogLevel 3

<Directory />
    Options +Includes Indexes +MultiViews FollowSymLinks
    AllowOverride None
    Order deny,allow
    Deny from all
    MultiviewsMatch Any
    SetOutputFilter INCLUDES
In /opt/apache/conf/unity.map is mentioned:
APPL /opt/appl/htdocs
In the directory /opt/appl/htdocs is:
test:/var/log/apache2 # ll /opt/appl/htdocs/index.*
-rw-r----- 1 hg3550m unity 887 Mar 27 10:12 /opt/appl/htdocs/index.shtml.de
-rw-r----- 1 hg3550m unity 893 Mar 27 10:12 /opt/appl/htdocs/index.shtml.en_US
test:/var/log/apache2 #
Unfortunatelly when I go to the page https://localhost/APPL/index.shtml
then it show me in the /var/log/apache2/error_log "Negotiation: discovered file(s) matching request: /opt/appl/htdocs/index.shtml (None could be negotiated)".
Rewrite Rule is working properly but negotiation is not working well.
When I am inserting following lines to the configuration file:
<Directory "/opt/appl/htdocs">
    Options +Includes +Multiviews
    AuthType TestAuth
    require auth-validation
    Satisfy any
then the negotiation is working.
I thought that all directories under DocumentRoot including RewriteMap has the same setting as <Directory /> flag, right?
Could you please explain me why I am getting error from Negotiation module? Error code which is mentioned in apache is HTTP 404.
Does it mean the for each directory which is not under /opt/apache/htdocs/ssldocs has to be mentioned special directive Directory?
What did I set incorrectly?

Best regards