Declarative support needs to be enabled in the HTML document by adding an attribute to the OpenUI5 bootstrap script tag.
Caution:
Deprecated as of UI5 version 1.120, replaced by XML View.
This is done as follows:
data-sap-ui-modules="sap.ui.core.plugin.DeclarativeSupport"
OpenUI5 then requires (loads) the plugin sap.ui.core.plugin.DeclarativeSupport. When started, the plugin parses and enhances special HTML tags in the HTML document. The complete bootstrap script tag for OpenUI5 (based on a CDN version) looks as follows:
<script id="sap-ui-bootstrap"
type="text/javascript"
src="resources/sap-ui-core.js"
data-sap-ui-theme="sap_horizon"
data-sap-ui-libs="sap.m"
data-sap-ui-modules="sap.ui.core.plugin.DeclarativeSupport"
>
</script>