hmc's primary purpose is to provide human-readable XML wrappers to a REST interface, to guide the user in how to interact with the interface. Similar to HTML, but stripped down for readability; generally on the commandline using a tool like HTTPie.

An XML element under the c: namespace is a hypermedia control provided by this package that tells the user what interactions on the given resource are possible.

There are five main elements that hmc provides. They generally try to mimic the existing standard of HTML:

• <c:Form>: analogous to HTML's <form>. It encloses a group of inputs, and generally describes which HTTP verb to use under the method attribute, e.g. POST or by default GET.
• <c:Input>: analogous to HTML's <input> type. It represents a single name-value pair. It may have validation attributes, similar to HTML: e.g. type, required, minlength. An <c:Input> (or a <c:Select>, or a <c:Map>) outside of a <c:Form> is not a valid input.
• <c:Select>: analogous to HTML's <select>. It represents an input with fixed options. The option list may be non-exaustive. It may take multiple options if the multiple attribute is set.
• <c:Link>: analogous to HTML's <a> hyperlink. It provides directions to other relevant resources.
• <c:Map>: Is the only element without an HTML analogue. A <c:Map> with name="foo" means that arbitrary name-value pairs may be provided under the namespace "foo" with bracket notation, e.g. foo[bar]=baz.

These elements can also be serialised to JSON for ease of querying, especially using jq.