But Wait Theres More Resources

So far, the design assumes that the write and delete actions are triggered in response to HTML form submissions. Where are those HTML forms going to come from? Because the forms need to be dynamically generated based on the name of the page they're modifying, they must be generated by the wiki program. This makes them a new type of resource. Contrary to what was stated earlier, BittyWiki actually serves two types of resources. Its primary job is to serve pages, but it must also serve HTML forms for manipulating those pages.

Unlike pages, forms can't be created, updated, or deleted by the user: they can only be read. (After they're read, however, they can be used to create, update or delete pages.) The forms should therefore be accessible through GET URLs.

Because the user will be requesting a form to write or delete a particular page, it makes sense to base the resource identifier for the form on that of the page. There are two ways of doing this. The first is to continue to append to the PATH_INFO of the identifier, so that the form to delete the page at /bittywiki.cgi/ MyPage is located at /wiki.cgi/MyPage/delete. The other way is to use the QUERY_STRING, so that that form is located at /wiki.cgi/MyPage?operation=delete.

There's no general right or wrong solution. However, because the "operation" keyword is already in use for the POST form submissions, and because the pages (not the forms) are the real point of a wiki, BittyWiki will implement the second strategy. The possible values will be the same as for the POST commands: write and delete.

To summarize: Each wiki page in BittyWiki boasts three associated resources. Each resource might behave differently in response to a GET and a POST, as shown in the following table.

Resource

What GET does

What POST does

/bittywiki.cgi/PageName

Displays the page if it exists; displays create form if not

Nothing

/bittywiki.cgi/PageName?operation=write

Displays edit form

Writes page, provides status

/bittywiki.cgi/PageName?operation=delete

Displays delete form

Deletes page, provides status

If no page name is specified (that is, someone GETs the bare resource /bittywiki.cgi/), the CGI will ask the core wiki code to retrieve the default page.

There are tradeoffs to consider when you're designing your resource identifiers and weighing PATH_INF0 againstQUERY_STRING. Both "/foo.cgi/clients/MegaCorp" and "/foo.cgi?client=MegaCorp" are legitimate REST identifiers for the same resource. The advantage of the first one is that it looks a lot nicer, more like a "real" resource. If you want to give the appearance of hierarchy in your data structure, nothing does it as well as a PATH_lNF0-based identifier scheme.

The problem is that you can't use that scheme in conjunction with an HTML form that lets you, for example, select MegaCorp from a list of clients. The destination of an HTML form needs to be defined at the time the form is printed, so the best you can do ahead of time would be /foo.cgi/, letting the web browser tack on "?client=MegaCorp" when the user submits the form. If your application has this problem, you might consider defining two resource identifiers for each of your resources: an identifier that uses PATH_INF0, and one that uses QUERY_STRING.

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