Revive old "Design Decisions".
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docs/source/devel/originaldesigndecisions.rst
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docs/source/devel/originaldesigndecisions.rst
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.. _design-decisions-chapter:
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==================
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Design Decisions
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==================
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.. contents:: Sections
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:local:
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This chapter talks a bit about design decisions.
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Why GNU MediaGoblin?
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====================
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Chris and Will on "Why GNU MediaGoblin":
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Chris came up with the name MediaGoblin. The name is pretty fun.
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It merges the idea that this is a Media hosting project with
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Goblin which sort of sounds like gobbling. Here's a piece of
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software that gobbles up your media for all to see.
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`According to Wikipedia <http://en.wikipedia.org/wiki/Goblin>`_, a
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goblin is:
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a legendary evil or mischievous illiterate creature, described
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as grotesquely evil or evil-like phantom
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So are we evil? No. Are we mischievous or illiterate? Not
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really. So what kind of goblin are we thinking about? We're
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thinking about these goblins:
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.. figure:: goblin.png
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:alt: Cute goblin with a beret.
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*Figure 1: Cute goblin with a beret. llustrated by Chris
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Webber*
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.. figure:: snugglygoblin.png
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:scale: 50%
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:alt: Snuggly goblin with a beret.
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*Figure 2: Snuggly goblin. Illustrated by Karen Rustad*
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Those are pretty cute goblins. Those are the kinds of goblins
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we're thinking about.
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Chris started doing work on the project after thinking about it
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for a year. Then, after talking with Matt and Rob, it became an
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official GNU project. Thus we now call it GNU MediaGoblin.
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That's a lot of letters, though, so in the interest of brevity and
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facilitating easier casual conversation and balancing that with
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what's important to us, we have the following rules:
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1. "GNU MediaGoblin" is the name we're going to use in all official
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capacities: web site, documentation, press releases, ...
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2. In casual conversation, it's ok to use more casual names.
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3. If you're writing about the project, we ask that you call it GNU
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MediaGoblin.
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4. If you don't like the name, we kindly ask you to take a deep
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breath, think a happy thought about cute little goblins playing
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on a playground and taking cute pictures of themselves, and let
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it go. (Will added this one.)
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Why Python
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==========
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Chris Webber on "Why Python":
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Because I know Python, love Python, am capable of actually making
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this thing happen in Python (I've worked on a lot of large free
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software web applications before in Python, including `Miro
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Community`_, the `Miro Guide`_, a large portion of `Creative
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Commons`_, and a whole bunch of things while working at `Imaginary
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Landscape`_). Me starting a project like this makes sense if it's
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done in Python.
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You might say that PHP is way more deployable, that Rails has way
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more cool developers riding around on fixie bikes---and all of
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those things are true. But I know Python, like Python, and think
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that Python is pretty great. I do think that deployment in Python
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is not as good as with PHP, but I think the days of shared hosting
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are (thankfully) coming to an end, and will probably be replaced
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by cheap virtual machines spun up on the fly for people who want
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that sort of stuff, and Python will be a huge part of that future,
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maybe even more than PHP will. The deployment tools are getting
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better. Maybe we can use something like Silver Lining. Maybe we
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can just distribute as ``.debs`` or ``.rpms``. We'll figure it
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out when we get there.
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Regardless, if I'm starting this project, which I am, it's gonna
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be in Python.
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.. _Miro Community: http://mirocommunity.org/
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.. _Miro Guide: http://miroguide.org/
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.. _Creative Commons: http://creativecommons.org/
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.. _Imaginary Landscape: http://www.imagescape.com/
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Why WSGI Minimalism
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===================
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Chris Webber on "Why WSGI Minimalism":
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If you notice in the technology list I list a lot of components
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that are very "django-like", but not actually `Django`_
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components. What can I say, I really like a lot of the ideas in
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Django! Which leads to the question: why not just use Django?
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While I really like Django's ideas and a lot of its components, I
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also feel that most of the best ideas in Django I want have been
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implemented as good or even better outside of Django. I could
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just use Django and replace the templating system with Jinja2, and
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the form system with wtforms, and the database with MongoDB and
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MongoKit, but at that point, how much of Django is really left?
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I also am sometimes saddened and irritated by how coupled all of
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Django's components are. Loosely coupled yes, but still coupled.
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WSGI has done a good job of providing a base layer for running
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applications on and if you know how to do it yourself [1]_, it's
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not hard or many lines of code at all to bind them together
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without any framework at all (not even say `Pylons`_, `Pyramid`_
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or `Flask`_ which I think are still great projects, especially for
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people who want this sort of thing but have no idea how to get
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started). And even at this already really early stage of writing
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MediaGoblin, that glue work is mostly done.
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Not to say I don't think Django isn't great for a lot of things.
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For a lot of stuff, it's still the best, but not for MediaGoblin,
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I think.
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One thing that Django does super well though is documentation. It
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still has some faults, but even with those considered I can hardly
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think of any other project in Python that has as nice of
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documentation as Django. It may be worth learning some lessons on
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documentation from Django [2]_, on that note.
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I'd really like to have a good, thorough hacking-howto and
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deployment-howto, especially in the former making some notes on
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how to make it easier for Django hackers to get started.
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.. _Django: http://www.djangoproject.com/
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.. _Pylons: http://pylonshq.com/
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.. _Pyramid: http://docs.pylonsproject.org/projects/pyramid/dev/
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.. _Flask: http://flask.pocoo.org/
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.. [1] http://pythonpaste.org/webob/do-it-yourself.html
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.. [2] http://pycon.blip.tv/file/4881071/
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Why MongoDB
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===========
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Chris Webber on "Why MongoDB":
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In case you were wondering, I am not a NOSQL fanboy, I do not go
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around telling people that MongoDB is web scale. Actually my
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choice for MongoDB isn't scalability, though scaling up really
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nicely is a pretty good feature and sets us up well in case large
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volume sites eventually do use MediaGoblin. But there's another
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side of scalability, and that's scaling down, which is important
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for federation, maybe even more important than scaling up in an
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ideal universe where everyone ran servers out of their own
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housing. As a memory-mapped database, MongoDB is pretty hungry,
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so actually I spent a lot of time debating whether the inability
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to scale down as nicely as something like SQL has with sqlite
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meant that it was out.
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But I decided in the end that I really want MongoDB, not for
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scalability, but for flexibility. Schema evolution pains in SQL
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are almost enough reason for me to want MongoDB, but not quite.
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The real reason is because I want the ability to eventually handle
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multiple media types through MediaGoblin, and also allow for
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plugins, without the rigidity of tables making that difficult. In
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other words, something like::
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{"title": "Me talking until you are bored",
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"description": "blah blah blah",
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"media_type": "audio",
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"media_data": {
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"length": "2:30",
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"codec": "OGG Vorbis"},
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"plugin_data": {
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"licensing": {
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"license": "http://creativecommons.org/licenses/by-sa/3.0/"}}}
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Being able to just dump media-specific information in a media_data
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hashtable is pretty great, and even better is having a plugin
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system where you can just let plugins have their own entire
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key-value space cleanly inside the document that doesn't interfere
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with anyone else's stuff. If we were to let plugins to deposit
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their own information inside the database, either we'd let plugins
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create their own tables which makes SQL migrations even harder
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than they already are, or we'd probably end up creating a table
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with a column for key, a column for value, and a column for type
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in one huge table called "plugin_data" or something similar. (Yo
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dawg, I heard you liked plugins, so I put a database in your
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database so you can query while you query.) Gross.
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I also don't want things to be too loose so that we forget or lose
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the structure of things, and that's one reason why I want to use
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MongoKit, because we can cleanly define a much structure as we
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want and verify that documents match that structure generally
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without adding too much bloat or overhead (MongoKit is a pretty
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lightweight wrapper and doesn't inject extra MongoKit-specific
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stuff into the database, which is nice and nicer than many other
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ORMs in that way).
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Why Sphinx for documentation
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============================
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Will Kahn-Greene on "Why Sphinx":
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`Sphinx`_ is a fantastic tool for organizing documentation for a
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Python-based project that makes it pretty easy to write docs that
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are readable in source form and can be "compiled" into HTML, LaTeX
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and other formats.
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There are other doc systems out there, but given that GNU
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MediaGoblin is being written in Python and I've done a ton of
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documentation using Sphinx, it makes sense to use Sphinx for now.
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.. _Sphinx: http://sphinx.pocoo.org/
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Why AGPLv3 and CC0?
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===================
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Chris, Brett, Will, Rob, Matt, et al curated into a story where
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everyone is the hero by Will on "Why AGPLv3 and CC0":
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The `AGPL v3`_ preserves the freedoms guaranteed by the GPL v3 in
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the context of software as a service. Using this license ensures
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that users of the service have the ability to examine the source,
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deploy their own instance, and implement their own version. This
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is really important to us and a core mission component of this
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project. Thus we decided that the software parts should be under
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this license.
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However, the project is made up of more than just software:
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there's CSS, images, and other output-related things. We wanted
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the templates/images/css side of the project all permissive and
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permissive in the same absolutely permissive way. We're waiving
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our copyrights to non-software things under the CC0 waiver.
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That brings us to the templates where there's some code and some
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output. The template engine we're using is called Jinja2. It
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mixes HTML markup with Python code to render the output of the
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software. We decided the templates are part of the output of the
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software and not the software itself. We wanted the output of the
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software to be licensed in a hassle-free way so that when someone
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deploys their own GNU MediaGoblin instance with their own
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templates, they don't have to deal with the copyleft aspects of
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the AGPLv3 and we'd be fine with that because the changes they're
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making are identity-related. So at first we decided to waive our
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copyrights to the templates with a CC0 waiver and then add an
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exception to the AGPLv3 for the software such that the templates
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can make calls into the software and yet be a separately licensed
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work. However, Brett brought up the question of whether this
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allows some unscrupulous person to make changes to the software
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through the templates in such a way that they're not bound by the
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AGPLv3: i.e. a loophole. We thought about this loophole and
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between this and the extra legalese involved in the exception to
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the AGPLv3, we decided that it's just way simpler if the templates
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were also licensed under the AGPLv3.
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Then we have the licensing for the documentation. Given that the
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documentation is tied to the software content-wise, we don't feel
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like we have to worry about ensuring freedom of the documentation
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or worry about attribution concerns. Thus we're waiving our
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copyrights to the documentation under CC0 as well.
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Lastly, we have branding. This covers logos and other things that
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are distinctive to GNU MediaGoblin that we feel represents this
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project. Since we don't currently have any branding, this is an
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open issue, but we're thinking we'll go with a CC BY-SA license.
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By licensing in this way, we make sure that users of the software
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receive the freedoms that the AGPLv3 ensures regardless of what
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fate befalls this project.
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So to summarize:
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* software (Python, JavaScript, HTML templates): licensed
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under AGPLv3
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* non-software things (CSS, images, video): copyrights waived
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under CC0 because this is output of the software
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* documentation: copyrights waived under CC0 because it's not part
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of the software
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* branding assets: we're kicking this can down the road, but
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probably CC BY-SA
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This is all codified in the ``COPYING`` file.
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.. _AGPL v3: http://www.gnu.org/licenses/agpl.html
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.. _CC0 v1: http://creativecommons.org/publicdomain/zero/1.0/
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Why (non-mandatory) copyright assignment?
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=========================================
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Chris Webber on "Why copyright assignment?":
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GNU MediaGoblin is a GNU project with non-mandatory but heavily
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encouraged copyright assignment to the FSF. Most, if not all, of
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the core contributors to GNU MediaGoblin will have done a
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copyright assignment, but unlike some other GNU projects, it isn't
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required here. We think this is the best choice for GNU
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MediaGoblin: it ensures that the Free Software Foundation may
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protect the software by enforcing the AGPL if the FSF sees fit,
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but it also means that we can immediately merge in changes from a
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new contributor. It also means that some significant non-FSF
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contributors might also be able to enforce the AGPL if seen fit.
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Again, assignment is not mandatory, but it is heavily encouraged,
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even incentivized: significant contributors who do a copyright
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assignment to the FSF are eligible to have a unique goblin drawing
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produced for them by the project's main founder, Christopher Allan
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Webber. See :ref:`contributing-howto-chapter` for details.
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@ -84,6 +84,7 @@ This chapter contains various information for developers.
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:maxdepth: 1
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devel/codebase
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devel/originaldesigndecisions
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Indices and tables
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