It is a request identifier as a path parameter.
<?xml version="1.0" encoding="UTF-8" ?>
<Resource xmlns="http://xml.metamug.net/resource/1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xml.metamug.net/resource/1.0 http://xml.metamug.net/schema/resource.xsd"
v="1.1">
<Desc>Contains information about movies.</Desc>
<!-- Collection GET Request /movie -->
<Request method="GET">
<Desc>Get info of all movies with ratings greater than 3.</Desc>
<Sql id="wellRatedMovies">
SELECT name,rating FROM movie
where rating gt 3.0
</Sql>
</Request>
<!-- Item GET Request /movie/{id} -->
<Request method="GET" item="true">
<Desc>Get info of movie with given id.</Desc>
<Sql id="allMovies">
SELECT * FROM movie where id=$id
</Sql>
</Request>
</Resource>
The above request executes the second request part when it receives a path with resource/id in it.