program or an executable program) but to a logical part (e.g. a command or a qualifier part) that has to be passed separately to the first part of the path that identifies an executable module or program managed by a web server; this is often used to select dynamic content (a document, etc.) or to tailor it as requested (see also: CGI and PATH_INFO, etc.). Example: URI: where: is the first part of the path (an executable module or program) and is the second part of the path named pathinfo, which is passed to the executable module or program named to select the requested document. An http or https URI containing a pathinfo part without a query part may also be referred to as a 'clean URL' whose last part may be a 'slug'. An optional component preceded by a question mark (?), consisting of a query string of non-hierarchical data. Its syntax is not well defined, but by convention is most often a sequence of attribute–value pairs separated by a delimiter. An optional component preceded by a hash (#). The fragment contains a fragment identifier providing direction to a secondary resource, such as a section heading in an article identified by the remainder of the URI. When the primary resource is an HTML document, the fragment is often an id attribute of a specific element, and web browsers will scroll this element into view. The scheme- or implementation-specific reserved character + may be used in the scheme, userinfo, host, path, query, and fragment, and the scheme- or implementation-specific reserved characters !, $, &, ', (, ), *, ,, ;, and = may be used in the userinfo, host, path, query, and fragment. Additionally, the generic reserved character : may be used in the userinfo, path, query and fragment, the generic reserved characters @ and / may be used in the path, query and fragment, and the generic reserved character ? may be used in the query and fragment. Example URIs The following figure displays example URIs and their component parts. DOIs (digital object identifiers) fit within the Handle System and fit within the URI system, as facilitated by appropriate syntax. URI references A URI reference is either a URI or a relative reference when it does not begin with a scheme component followed by a colon (:). A path segment that contains a colon character (e.g., foo:bar) cannot be