Weceem is built with Grails which provides a technology called Groovy Server Pages. In essence, it allows you to embed special tags in the content to perform special functions or logic. Some content types in Weceem (Template, Widget and HTML) support the use of these tags to provide advanced features.
To users of JSP (Java Server Pages) this will be a familiar concept.
These custom tags or "GSP tags" as they are called, use the XML namespacing syntax:
Search: <wcm:search/>
The "wcm:" prefix is the Weceem tag namespace. This tells you it is a Weceem-specific tag you are using. Grails provides its own "g:" namespace for basic built-in functions like link creation, iteration over items in a list and so on.
Attributes can be passed to these tags as you would with HTML, with the addition of a Groovy-based "Expression Language" (EL) that lets you pass around variables that are available to the page or execute small pieces of code to perform calculations. These are put inside a dollar and brace syntax "${...}":
<g:each in="${node.lineage}">
${node.title.encodeAsHTML()}<br/>
</g:each>
The above would iterate over every item in the "lineage" property of the "node" object. The "node" object represents the current content node being rendered. See the reference section on page variables for more details of the available objects.
You will see here also that the EL can be used outside of tag attributes, to render information into the page output. As a side-note, the encodeAsHTML() method called in that example escapes the resulting title text so that it is safe for inclusion in HTML output (it escapes special characters to HTML entities). This encodeAs functionality is provided by Grails.
Using these features you can code your Template and Widget nodes to perform all kinds of powerful functions, from listing child nodes of the current page, to generating RSS feeds. See the Weceem tag reference for full details.
