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uPath to Relative


Disclaimer

This essay does not describe an existing computer program, just one that should exist. This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have prepared to help you is right here.

This project outline is not like the artificial, tidy little problems you are spoon-fed in school, when all the facts you need are included, nothing extraneous is mentioned, the answer is fully specified, along with hints to nudge you toward a single expected canonical solution. This project is much more like the real world of messy problems where it is up to you to fully the define the end point, or a series of ever more difficult versions of this project and research the information yourself to solve them.

Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; or give you any additional materials. I have too many other projects of my own.

Though I am a programmer by profession, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project in any way you please and to keep all the profits from your endeavour.

Please do not email me about this project without reading the disclaimer above.

Composing relative URLs (Uniform Resource Locators) in a document is quite a bear e.g.

href="../../../../../x/y/z/a.html"

It requires excessive mental computation to compose and proofread. Relative URLs are also unstable if you move documents around in the tree.

It would be much more convenient to be able to specify:

href="/w/x/y/z/a.html"

I call these uPaths for url paths. They are relative to the root, both online and in a local mirror. They have a lead / to indicate they are not relative and not full URLs.

I pondered why browsers do not support this convenient notation already. On-line, they know where the root is so they can internally convert to relative or absolute URLs. Off-line, officially they do not. Yet
<link rel="home" href="../../../index.html">
so long as it is encoded with a relative link, gives the necessary information.

Perhaps there needs to be something more official to tell the browser where the root is when it is viewing an offline mirror. This notation could make proofreading links so much easier.

In the Meantime

Maybe a few centuries from now w3.org will change the URL (Uniform Resource Locator) spec. In the meantime, what could we do? We could code our trees of documents using uPaths, then just before we upload them, run a utility to convert the uPath references to relative. That is your job.

Use regexes or indexOf logic to find the unconverted uPath references. You can cannibalise the core uPath-to-relative logic from com.mindprod.htmlmacros.support.Tools. You can cannibalise the logic to span the tree of documents and process each one from com.mindprod.common18.CommandLine. You can use com.mindprod.hunkio.HunkIO to efficiently read and write each file. You can use com.mindprod.htmlmacros.support.Lazy to implement a scheme to avoid processing files that have already been processed.

The problem with that approach is the uPath notation is lost when you convert it to relative. If you rearrange your tree of files, the relative links will no longer work. You could handle it the way I do in HTML (Hypertext Markup Language) static macros. You use a comment of the form

<!-- macro Link /abc/def.htm/ "an interesting place" -->

to be re-expanded later.

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