diff --git a/apache/metadata.yml b/apache/metadata.yml
index ece28a7..50131bf 100644
--- a/apache/metadata.yml
+++ b/apache/metadata.yml
@@ -18,3 +18,19 @@ config-resources:
 provides:
   web-proxy:
     tech-dep: "reversed"
+uses:
+  log-rotate:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: recommended
+    auto: pair
+    solves:
+      disk-leak: "/var/log/apache2"
+  cert-provider:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: optional
+    auto: pair
+    limit: n
+    solves:
+      feature: "SSL certificate generation"
diff --git a/cron/metadata.yml b/cron/metadata.yml
index 7fc2a6d..9e9abcb 100644
--- a/cron/metadata.yml
+++ b/cron/metadata.yml
@@ -13,3 +13,12 @@ host-resources:
 provides:
   schedule-command:
     tech-dep: False
+
+uses:   ## optional
+  log-rotate:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: optional
+    solves:
+      disk-leak: "/var/log/cron"
+    #default-options:
diff --git a/letsencrypt/metadata.yml b/letsencrypt/metadata.yml
index 6b225f6..70a8065 100644
--- a/letsencrypt/metadata.yml
+++ b/letsencrypt/metadata.yml
@@ -7,3 +7,21 @@ data-resources:
   - /etc/letsencrypt        ## yes certificates are stored here, this is data
   - /var/log/letsencrypt    ## logs
   - /var/lib/tldextract     ## latest data about TLDs, this is used by lexicon...
+provides:
+  cert-provider:
+uses:
+  log-rotate:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: optional
+    auto: pair
+    solves:
+      disk-leak: "/var/log/letsencrypt"
+    #default-options:
+  schedule-command:
+    constraint: recommended
+    auto: pair
+    solves:
+      missing-feature: "Automatic certificate renewal"
+    default-options:
+      schedule: "30 3 * * 7"  ## schedule log renewal every week
diff --git a/logrotate/hooks/schedule_command-relation-joined b/logrotate/hooks/schedule_command-relation-joined
index 2e61de2..f9950e7 100755
--- a/logrotate/hooks/schedule_command-relation-joined
+++ b/logrotate/hooks/schedule_command-relation-joined
@@ -13,8 +13,6 @@ label=launch-$SERVICE_NAME
 DST=$CONFIGSTORE/$TARGET_SERVICE_NAME/etc/cron/$label
 schedule=$(relation-get schedule) || true
 
-## It should really stay at midnight as most logs are dated
-schedule=${schedule:-0 0 * * *}
 if ! echo "$schedule" | egrep '^\s*(([0-9/,*-]+\s+){4,4}[0-9/,*-]+|@[a-z]+)\s*$' >/dev/null 2>&1; then
     err "Unrecognized schedule '$schedule'."
     exit 1
diff --git a/logrotate/metadata.yml b/logrotate/metadata.yml
index 1715fbc..bbcc9a2 100644
--- a/logrotate/metadata.yml
+++ b/logrotate/metadata.yml
@@ -2,12 +2,17 @@ description: Log Rotation Service
 type: run-once
 data-resources:
   - /var/lib/logrotate
-requires:
-  schedule-command:
-    interface: schedule-command
 ## YYY: probably not useful anymore
 # charm-resources:
 #   - /etc/cron.daily/logrotate
 provides:
   log-rotate:
     tech-dep: "reversed"
+
+uses:
+  schedule-command:
+    constraint: required
+    solves:
+      missing-feature: "scheduling of log rotation"
+    default-options:
+      schedule: "0 0 * * *"  ## It should really stay at midnight as most logs are dated
\ No newline at end of file
diff --git a/odoo-tecnativa/metadata.yml b/odoo-tecnativa/metadata.yml
index 85fa614..44765ac 100644
--- a/odoo-tecnativa/metadata.yml
+++ b/odoo-tecnativa/metadata.yml
@@ -18,6 +18,32 @@ docker-compose:
     INITIAL_LANG: fr_FR
   restart: unless-stopped
 
+uses:
+  postgres-database:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: required
+    auto: pair
+    solves:
+      database: "main storage"
+    #default-options:
+  log-rotate:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: recommended
+    auto: pair
+    solves:
+      disk-leak: "/var/log/odoo"
+    #default-options:
+  web-proxy:
+    #constraint: required | recommended | optional
+    #auto: pair | summon | none ## default: pair
+    constraint: recommended
+    auto: pair
+    solves:
+      proxy: "Public access"
+    #default-options:
+
 # network-isolation:
 #   whitelist:  ## required external services used by this service
 #     - www.google.com
diff --git a/postgres/metadata.yml b/postgres/metadata.yml
index 52a681e..e5eea48 100644
--- a/postgres/metadata.yml
+++ b/postgres/metadata.yml
@@ -2,3 +2,5 @@ summary: "Postgres server"
 maintainer: "Valentin Lab <valentin.lab@kalysto.org>"
 data-resources:
   - /var/lib/postgresql/data
+provides:
+  postgres-database:
\ No newline at end of file