diff --git a/README b/README
index 9d2b6a1..9f607ac 100644
--- a/README
+++ b/README
@@ -1,7 +1,14 @@
-YMS - Yacht Management System
-Prototype
+YMS - Open Source Yacht Management System
+Preview Version
 
-Many features are incomplete, buggy or missing.
+Free, self-hosted software for managing your boat's equipment,
+inventory, documents, maintenance and tasks.
+
+Your boat. Your data. Your software.
+
+
+This is work in progress:
+Many features can be incomplete, buggy or missing.
 Use at your own risk!
 
 If inserting a new user you have also to insert a setting value
@@ -9,8 +16,8 @@ to assign boat 0.
 
 To set your own passwords via console there is a helper script
   ymspass.py
-
 Use it to get an SQL-statement for changing passwords.
 
 For further information go to https://computerclub.hoogi.de/yms
 (currently german only)
+
diff --git a/db/mariadb.sql b/db/mariadb.sql
index 4bbcb22..1d171e1 100644
--- a/db/mariadb.sql
+++ b/db/mariadb.sql
@@ -5,8 +5,10 @@
 
 /* TODO
    - check all values if unsigned can be used or not
-   - implement foreign keys where possible
+   - implement foreign keys where missing and possible
+     - add referential actions where appropriate
    - rename provisions to provision(?)
+   - review defaults
    */
 
 /* User
@@ -125,9 +127,17 @@ CREATE TABLE storage (
     angle smallint(4) NOT NULL DEFAULT 0,
     color char(6) DEFAULT NULL,
     remarks varchar(150) DEFAULT NULL,
-    PRIMARY KEY (sid)
+    PRIMARY KEY (sid),
+    FOREIGN KEY fk_storage_vessel (vid)
+        REFERENCES vessel(vid)
 ) ENGINE=InnoDB;
 
+/* intentionally after storage creation */
+ALTER TABLE vessel
+    ADD CONSTRAINT fk_vessel_storage
+    FOREIGN KEY (sid_default)
+    REFERENCES storage(sid);
+
 CREATE TABLE tag (
     tagid smallint(6) UNSIGNED NOT NULL AUTO_INCREMENT,
     tagname varchar(20) NOT NULL,
@@ -141,7 +151,10 @@ CREATE TABLE tagref (
     tagid smallint(6) UNSIGNED NOT NULL,
     objid int(10) UNSIGNED NOT NULL,
     objtype enum('equip','inv','prov','doc', 'proj', 'task', 'maint') NOT NULL,
-    PRIMARY KEY (tagid, objid, objtype)
+    PRIMARY KEY (tagid, objid, objtype),
+    FOREIGN KEY fk_tagref_tag (tagid)
+        REFERENCES tag(tagid)
+        ON DELETE CASCADE
 ) ENGINE=InnoDB;
 
 /* TODO Boxes can be nested via parent
@@ -157,7 +170,9 @@ CREATE TABLE box (
     weight float(5,2) UNSIGNED DEFAULT NULL,
     remarks varchar(150) DEFAULT NULL,
     PRIMARY KEY (boxid),
-    INDEX ix_label (label)
+    INDEX ix_label (label),
+    FOREIGN KEY fk_box_storage (sid)
+        REFERENCES storage(sid)
 ) ENGINE=InnoDB;
 
 CREATE TABLE equipment (
@@ -165,7 +180,7 @@ CREATE TABLE equipment (
     vid smallint(6) NOT NULL DEFAULT 1,
     ename varchar(80) NOT NULL,
     shortname varchar(20) DEFAULT NULL,
-    model varchar(40),
+    model varchar(40) DEFAULT NULL,
     ecat tinyint(3) DEFAULT NULL,
     serial varchar(30) DEFAULT NULL,
     supplier smallint(6) DEFAULT NULL,
@@ -175,25 +190,21 @@ CREATE TABLE equipment (
     weight float(5,2) UNSIGNED DEFAULT NULL,
     remarks varchar(150) DEFAULT NULL,
     flags set('ordered','removed','deleted') DEFAULT NULL,
-    PRIMARY KEY(eid)
+    PRIMARY KEY(eid),
+    FOREIGN KEY fk_equipment_vessel (vid)
+        REFERENCES vessel(vid)
+        ON DELETE RESTRICT,
+    FOREIGN KEY fk_equipment_supplier (supplier)
+        REFERENCES company(compid)
+        ON DELETE RESTRICT
 ) ENGINE=InnoDB;
 
-/*
-convert to
-sid   SMALLINT UNSIGNED NULL,
-boxid SMALLINT UNSIGNED NULL,
-CHECK (
-    (sid IS NOT NULL AND boxid IS NULL)
-    OR
-    (sid IS NULL AND boxid IS NOT NULL)
-)
-*/
 CREATE TABLE inventory (
     invid int(10) UNSIGNED NOT NULL AUTO_INCREMENT,
     invname varchar(80) NOT NULL,
     conttype enum('storage','box') NOT NULL DEFAULT 'storage',
-    sid smallint(6) UNSIGNED NOT NULL DEFAULT 1,
-    boxid smallint(6) UNSIGNED NOT NULL DEFAULT 1,
+    sid smallint(6) UNSIGNED DEFAULT NULL,
+    boxid smallint(6) UNSIGNED DEFAULT NULL,
     eid smallint(6) UNSIGNED DEFAULT NULL,
     number smallint(6) UNSIGNED NOT NULL DEFAULT 1,
     weight float(5,2) UNSIGNED DEFAULT NULL,
@@ -203,7 +214,18 @@ CREATE TABLE inventory (
     remarks varchar(150) DEFAULT NULL,
     flags set('ordered','removed','deleted') DEFAULT NULL,
     PRIMARY KEY (invid),
-    INDEX ix_invname (invname)
+    INDEX ix_invname (invname),
+    FOREIGN KEY fk_inventory_storage (sid)
+        REFERENCES storage(sid),
+    FOREIGN KEY fk_inventory_box (boxid)
+        REFERENCES box(boxid),
+    FOREIGN KEY fk_inventory_equipment (eid)
+        REFERENCES equipment(eid)
+    CHECK (
+        (sid IS NOT NULL AND boxid IS NULL)
+        OR
+        (sid IS NULL AND boxid IS NOT NULL)
+    )
 ) ENGINE=InnoDB;
 
 CREATE TABLE cable (
@@ -222,7 +244,13 @@ CREATE TABLE cable (
     cablecond enum('unknown','new','excellent','good','fair','bad','repairable','defect') NOT NULL default 'unknown',
     remarks varchar(150) DEFAULT NULL,
     PRIMARY KEY (cableid),
-    INDEX ix_cablename (vid, cablename)
+    INDEX ix_cablename (vid, cablename),
+    FOREIGN KEY fk_cable_vessel (vid)
+        REFERENCES vessel(vid),
+    FOREIGN KEY fk_cable_supplier (supplier)
+        REFERENCES company(compid),
+    FOREIGN KEY fk_cable_manufacturer (manufacturer)
+        REFERENCES company(compid)
 ) ENGINE=InnoDB;
 
 CREATE table fuse (
@@ -237,7 +265,13 @@ CREATE table fuse (
     description varchar(60) DEFAULT NULL,
     remarks varchar(150) DEFAULT NULL,
     PRIMARY KEY (fuseid),
-    UNIQUE INDEX ix_fusenumber (vid, fnumber)
+    UNIQUE INDEX ix_fusenumber (vid, fnumber),
+    FOREIGN KEY fk_fuse_vessel (vid)
+        REFERENCES vessel(vid),
+    FOREIGN KEY fk_fuse_cable (cableid)
+        REFERENCES cable(cableid),
+    FOREIGN KEY fk_fuse_equipment (eid)
+        REFERENCES equipment(eid)
 ) ENGINE=InnoDB;
 
 -- change vals to decimal(12,4)?
@@ -245,6 +279,7 @@ CREATE TABLE measurement (
     mid smallint(6) NOT NULL AUTO_INCREMENT,
     mname varchar(80) NOT NULL,
     vid smallint(6) NOT NULL DEFAULT 1,
+    eid smallint(6) UNSIGNED DEFAULT NULL,
     nval tinyint(1) UNSIGNED NOT NULL DEFAULT 1,
     val1 int(10) NOT NULL,
     val2 int(10) DEFAULT NULL,
@@ -253,8 +288,11 @@ CREATE TABLE measurement (
     accuracy enum('unknown','precise','normal','rough','estimated') NOT NULL DEFAULT 'unknown',
     mdate date DEFAULT NULL,
     note varchar(80) DEFAULT NULL,
-    eid smallint(6) UNSIGNED DEFAULT NULL,
-    PRIMARY KEY (mid)
+    PRIMARY KEY (mid),
+    FOREIGN KEY fk_measurement_vessel (vid)
+        REFERENCES vessel(vid),
+    FOREIGN KEY fk_measurement_equipment (eid)
+        REFERENCES equipment(eid)
 ) ENGINE=InnoDB;
 
 CREATE TABLE provisions (
@@ -273,7 +311,11 @@ CREATE TABLE provisions (
     shelflife date DEFAULT NULL,
     price decimal(12,2) DEFAULT NULL,
     remarks varchar(150) DEFAULT NULL,
-    PRIMARY KEY (provid)
+    PRIMARY KEY (provid),
+    FOREIGN KEY fk_provisions_storage (sid)
+        REFERENCES storage(sid),
+    FOREIGN KEY fk_provisions_box (boxid)
+        REFERENCES box(boxid)
 ) ENGINE=InnoDB;
 
 /* TODO
@@ -322,9 +364,17 @@ CREATE TABLE maintenance (
     eid smallint(6) UNSIGNED DEFAULT NULL,
     series smallint(6) DEFAULT NULL,
     activities varchar(40) NOT NULL,
+    plan_date DATE DEFAULT NULL,
+    completion_date DATE DEFAULT NULL,
+    interval_hours smallint(6) DEFAULT NULL,
+    last_hours int(10) DEFAULT NULL,
     remarks varchar(150) DEFAULT NULL,
     maintstate enum('new','planned','ongoing','done') NOT NULL DEFAULT 'new',
-    PRIMARY KEY (maintid)
+    PRIMARY KEY (maintid),
+    FOREIGN KEY fk_maintenance_vessel (vid)
+        REFERENCES vessel(vid),
+    FOREIGN KEY fk_maintenance_equipment (eid)
+        REFERENCES equipment(eid)
 ) ENGINE=InnoDB;
 
 /* TODO? time recording */
@@ -340,9 +390,14 @@ CREATE TABLE project (
     costs_final decimal(12,2) DEFAULT NULL,
     remarks varchar(150) DEFAULT NULL,
     projstate enum('new','plan','ongoing','paused','finished') NOT NULL DEFAULT 'new',
-    PRIMARY KEY (projid)
+    PRIMARY KEY (projid),
+    FOREIGN KEY fk_project_vessel (vid)
+        REFERENCES vessel(vid),
+    FOREIGN KEY fk_project_user (responsible)
+        REFERENCES user(userid)
 ) ENGINE=InnoDB;
 
+/* TODO  executed_by : company or user? or both? */
 CREATE TABLE task (
     taskid int(10) NOT NULL AUTO_INCREMENT,
     vid smallint(6) DEFAULT NULL,
@@ -356,13 +411,16 @@ CREATE TABLE task (
     started datetime DEFAULT NULL,
     finished datetime DEFAULT NULL,
     responsible smallint(6) NOT NULL,
-    /* TODO  executed_by : company or user? or both? */
     PRIMARY KEY (taskid),
     FOREIGN KEY fk_task_user (responsible)
-        REFERENCES user(userid)
+        REFERENCES user(userid),
+    FOREIGN KEY fk_task_vessel (vid)
+        REFERENCES vessel(vid),
+    FOREIGN KEY fk_task_project (projid)
+        REFERENCES project(projid)
 ) ENGINE=InnoDB;
 
-/* Notes can be assigned to tasks,maintenances and equipment */
+/* Notes can be assigned to tasks, maintenances and equipment */
 CREATE TABLE note (
     noteid int(10) NOT NULL AUTO_INCREMENT,
     notetype enum('task','maint','equip') NOT NULL DEFAULT 'task',
@@ -376,28 +434,38 @@ CREATE TABLE checklist (
     title varchar(30) NOT NULL,
     parent smallint(6) DEFAULT NULL,
     clstate enum('new','open','closed') NOT NULL DEFAULT 'new',
-    PRIMARY KEY (clid)
+    PRIMARY KEY (clid),
+    FOREIGN KEY fk_checklist_parent (parent)
+       REFERENCES checklist(clid)
+) ENGINE=InnoDB;
+
+CREATE TABLE checkgroup (
+    groupid smallint(6) UNSIGNED NOT NULL,
+    title varchar(30) NOT NULL,
+    PRIMARY KEY (groupid)
 ) ENGINE=InnoDB;
 
 CREATE TABLE checkitem (
     checkid int(10) NOT NULL AUTO_INCREMENT,
     checkname varchar(60) NOT NULL,
-    groupid tinyint(3) DEFAULT NULL,
+    groupid smallint(6) UNSIGNED DEFAULT NULL,
     checkresult enum('unchecked','checked','unused') NOT NULL DEFAULT 'unused',
-    PRIMARY KEY (checkid)
+    PRIMARY KEY (checkid),
+    FOREIGN KEY fk_checkitem_group (groupid)
+        REFERENCES checkgroup(groupid)
 ) ENGINE=InnoDB;
 
 CREATE TABLE checkref (
     clid smallint(6) NOT NULL,
     checkid int(10) NOT NULL,
     sort smallint(6) DEFAULT NULL,
-    PRIMARY KEY (clid, checkid)
-) ENGINE=InnoDB;
-
-CREATE TABLE checkgroup (
-    groupid int(10) NOT NULL,
-    title varchar(30) NOT NULL,
-    PRIMARY KEY (groupid)
+    PRIMARY KEY (clid, checkid),
+    FOREIGN KEY fk_checkref_checklist (clid)
+        REFERENCES checklist(clid)
+        ON DELETE CASCADE,
+    FOREIGN KEY fk_checkref_checkitem (checkid)
+        REFERENCES checkitem(checkid)
+        ON DELETE CASCADE
 ) ENGINE=InnoDB;
 
 /* Expansion for future use: signalk mapping (just an idea) */
@@ -410,5 +478,7 @@ CREATE TABLE signalk (
     skpath varchar(255) NOT NULL,
     PRIMARY KEY (skid),
     UNIQUE KEY ix_signalk
-        (vid, objtype, objid, datatype)
+        (vid, objtype, objid, datatype),
+    FOREIGN KEY fk_signalk_vessel (vid)
+        REFERENCES vessel(vid)
 ) ENGINE=InnoDB;
diff --git a/install.sh b/install.sh
index 7f67c76..c838c94 100755
--- a/install.sh
+++ b/install.sh
@@ -7,6 +7,7 @@ BINDIR="${PREFIX}/bin"
 DESKTOPDIR="${PREFIX}/share/applications"
 ICONDIR="${PREFIX}/share/icons/hicolor"
 DOCDIR="${PREFIX}/share/doc/yms"
+MANDIR="${PREFIX}/usr/local/share/man/man1"
 LOCALEDIR="${PREFIX}/share/locale"
 
 SOURCEDIR=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
@@ -76,6 +77,9 @@ install -m 0644 \
 install -m 0644 \
     "${SOURCEDIR}/COPYING" \
     "${DOCDIR}/COPYING"
+install -m 0644 \
+    "${SOURCEDIR}/yms.1" \
+    "${MANDIR}/yms.1"
 
 echo "Installing translations..."
 make translation
diff --git a/webgui/globals.inc b/webgui/globals.inc
index 8a70c25..d7fe4e5 100644
--- a/webgui/globals.inc
+++ b/webgui/globals.inc
@@ -783,7 +783,7 @@ function db_get_options($ddid, $orderby = '', $short = False, $default = NULL) {
     $sth = $pdo->prepare($sql);
     $sth->execute([$ddid]);
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $rec) {
-        $list[$rec[0]] = $rec[1];
+        $list[$rec[0]] = h($rec[1]);
     }
     return $list;
 }
@@ -793,7 +793,7 @@ function db_get_opt_vessel() {
     $list = array();
     $sth = $pdo->query("SELECT vid, vesselname, model FROM vessel ORDER BY vid");
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $row) {
-         $list[$rec[0]] = $rec[1];
+         $list[$row[0]] = h($row[1]);
     }
     return $list;
 }
@@ -811,7 +811,7 @@ function db_get_opt_storage($vid) {
         $g_error->Add($e->getMessage());
     }
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $rec) {
-        $list[$rec[0]] = $rec[1];
+        $list[$rec[0]] = h($rec[1]);
     }
     return $list;
 }
@@ -832,7 +832,7 @@ function db_get_opt_box($vid, $exclude=[]) {
     }
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $rec) {
         if (! in_array($rec[0], $exclude)) {
-            $list[$rec[0]] = $rec[1] . ($rec[2] ? ' - '. $rec[2] : '');
+            $list[$rec[0]] = h($rec[1]) . ($rec[2] ? ' - '. h($rec[2]) : '');
         }
     }
     return $list;
@@ -855,7 +855,7 @@ function db_get_opt_equip($vid, $default=NULL, $exclude=[]) {
     }
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $rec) {
         if (! in_array($rec[0], $exclude)) {
-            $list[$rec[0]] = $rec[1];
+            $list[$rec[0]] = h($rec[1]);
         }
     }
     return $list;
@@ -871,7 +871,7 @@ function db_get_opt_manuf($default=NULL) {
     $sql = "SELECT compid, compname FROM company WHERE comptype=2 ORDER BY compname";
     $sth = $pdo->query($sql);
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $row) {
-        $list[$row[0]] = $row[1];
+        $list[$row[0]] = h($row[1]);
     }
     return $list;
 }
@@ -886,7 +886,7 @@ function db_get_opt_supp($default=NULL) {
     $sql = "SELECT compid, compname FROM company WHERE comptype=1 ORDER BY compname";
     $sth = $pdo->query($sql);
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $row) {
-        $list[$row[0]] = $row[1];
+        $list[$row[0]] = h($row[1]);
     }
     return $list;
 }
@@ -901,7 +901,7 @@ function db_get_opt_user($userid, $default=NULL) {
     $sql = "SELECT userid, displayname FROM user WHERE userid>0 ORDER BY displayname";
     $sth = $pdo->query($sql);
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $row) {
-        $list[$row[0]] = $row[1];
+        $list[$row[0]] = h($row[1]);
     }
     return $list;
 }
@@ -931,7 +931,7 @@ function db_get_opt_proj($vid, $exclude=[], $default=NULL) {
         $g_error->Add($e->getMessage());
     }
     foreach ($sth->fetchAll(PDO::FETCH_NUM) as $rec) {
-        $list[$rec[0]] = $rec[1];
+        $list[$rec[0]] = h($rec[1]);
     }
     return $list;
 }
@@ -1296,6 +1296,11 @@ function format_measurement($n, $unit, $v1, $v2, $v3) {
 
 // ========== COMMON FUNCTIONS ================================================
 
+function h($value) {
+    // escape value coming from db for safe html output
+    return htmlspecialchars($value, ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');
+}
+
 function header_location($location, $message=NULL) {
     if (is_array($message)) {
         $valid_keys = array('succ', 'info', 'warn', 'err');
diff --git a/webgui/inventory.php b/webgui/inventory.php
index 8888bc8..d4670e8 100644
--- a/webgui/inventory.php
+++ b/webgui/inventory.php
@@ -226,7 +226,7 @@ $opt_special = array(
   -2 => _('― all ―'),
 );
 foreach ($opt_special + $opt_invcond as $k => $v) {
-    echo '<option value="', $k,'"';
+    echo '<option value="', h($k), '"';
     if ($k == $flt->cond) {
         echo ' selected';
     }
@@ -237,7 +237,7 @@ foreach ($opt_special + $opt_invcond as $k => $v) {
         </div>
         <div class="d-flex flex-nowrap gap-2">
             <label for="flt_txt">Text</label>
-            <input type="text" class="form-control" name="flt_txt" size="15" maxlength="30" value="<?=$flt->txt ?>">
+            <input type="text" class="form-control" name="flt_txt" size="15" maxlength="30" value="<?=h($flt->txt)?>">
         </div>
     </div>
     <div class="card-footer">
diff --git a/yms.1 b/yms.1
new file mode 100644
index 0000000..703b1ad
--- /dev/null
+++ b/yms.1
@@ -0,0 +1,103 @@
+.TH YMS 1 "August 2026" "YMS 0.2" "User Commands"
+.SH NAME
+yms - Yacht Management Software
+.SH SYNOPSIS
+.B yms
+.SH DESCRIPTION
+.B YMS
+(Yacht Management Software) is free and open-source software for
+managing yachts, sailboats and their equipment.
+
+YMS is designed for managing yachts and sailboats, including
+equipment, inventory, storage locations, documents, maintenance,
+tasks, projects, provisions and technical data.
+
+The application uses MariaDB for structured application data.
+User-managed photos and documents are stored in the local filesystem.
+.SH FEATURES
+YMS provides the following functionality:
+.TP
+.B Equipment and inventory management
+Manage equipment and inventory belonging to the yacht.
+.TP
+.B Storage locations
+Organize equipment and inventory by physical storage location.
+.TP
+.B Documents and manuals
+Manage documents and manuals associated with the yacht and its
+equipment.
+.TP
+.B Maintenance and service history
+Record maintenance activities and service history.
+.TP
+.B Tasks and projects
+Manage tasks and projects related to the yacht.
+.TP
+.B Provisions and consumables
+Manage provisions, supplies and consumable items.
+.TP
+.B Technical data and measurements
+Store technical information, measurements and other data associated
+with the yacht.
+.SH DATABASE
+YMS uses MariaDB to store its structured application data.
+
+The MariaDB server must be available to the YMS application when
+the application is running.
+.SH FILES
+.TP
+.I ~/.config/ymsgui.conf
+Per-user configuration file for the YMS graphical user interface.
+
+.TP
+.I /var/local/yms/
+Persistent storage for files managed by YMS.
+
+The directory contains photos, documents and other media associated
+with the managed yacht. Supported file formats include JPEG, PNG,
+SVG and PDF.
+.SH BACKUP
+YMS stores application data in two separate locations.
+
+The directory
+.I /var/local/yms/
+contains user-managed photos and documents and should be included
+in regular backups.
+
+The structured application data is stored in MariaDB and must be
+backed up using an appropriate MariaDB backup procedure.
+
+.SH REQUIREMENTS
+YMS requires a graphical desktop environment with GTK3 support.
+
+The application requires Python and the GTK3 Python bindings.
+A MariaDB server is required for database access.
+
+.SH OPEN SOURCE
+YMS is free and open-source software.
+
+The source code is available from the YMS Git repository:
+.UR https://git.hoogi.de/thooge/YMS
+.UE
+.SH VERSION
+This manual describes YMS version 0.2.
+.SH PROJECT
+The YMS project homepage is available at:
+.UR https://yms.hoogi.de/
+.UE
+
+A live demonstration is available at:
+.UR https://www.hoogi.de/ymsdemo
+.UE
+
+German-language documentation is available at:
+.UR https://computerclub.hoogi.de/yms
+.UE
+.SH BUGS
+Please report bugs and contribute improvements through thread in Segeln-Forum or
+by submitting a mail
+.SH AUTHOR
+YMS is developed by Thomas Hooge / thomas@hoogi.de.
+.SH COPYRIGHT
+YMS is free and open-source software. See the project repository for
+license and copyright information.