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Algorithm for OpenStreetMap ODbL transition.

branch: master
README.md

Introduction

This is example (but working) code for the algorithm for the transition from CC-BY-SA to ODbL data. At this stage all the methods are mocked out, but future development will add the ability to run this against an apidb format database, or possibly a live API.

Requirements

To run this, you'll need Ruby (probably >=1.9.3) and some gems, which you can install with bundle install. Then you'll be able to run:

ruby test.rb

which will run the full range of unit tests. The test files can also be individually run to concentrate on some aspects of the suite.

Tools

A simple command-line tool, check_history.rb, is provided to query an API and return information about the actions that the bot would execute, if it were running for real. If you find any results from this which are not as expected, then they would make good unit tests. Run ruby check_history.rb --help for more information on running the tool, and on the available options.

Test-Driven Development

This code is intended to be read as a test-driven development. It's very hard to read most code when it implements a complex algorithm, especially when it is expected to be read by anyone not fluent in the language of choice (i.e: Ruby). In order to improve the understandability of the code, this project is intended to be test-driven, with well-commented tests to define the functionality. Hopefully these tests are quite easy to read, without being a ruby expert.

Tests can be found in the various files prefixed 'test_'. For example tests_node.rb contains a set of tests to run just involving nodes, and this is a good place to start. You'll find tests which describe nodes being created, moved, and having tags changed by various users (license change agreers and disagreers in various combinations). A test then the gives the expected resulting actions which a bot should be deciding upon, to put the node in a clean state, and to redact versions from the editing history.

Actions

The main algorithm in the code, in change_bot.rb takes the history of an element and turns this into a set of "actions", where each action is one of:

  1. Edit[new object]. This will be turned into an edit which is pushed to the API. Note that the version number should be equal to the object that this will be applied on top of. Also, the changeset ID should be -1.
  2. Delete[class, id]. This will be turned into a delete request and pushed to the API. Note that this and Edit are pretty much mutually exclusive.
  3. Redact[class, id, version, visibility]. This will be a call to the special API call which hides a version in the history, and means that it won't be distributed any more.

The redaction visibility has values :hidden and :visible and these may have different effects eventually. The intended meanings are:

  • Hidden: This version does not contribute to the final version of the object and must be completely hidden.
  • Visible: This version contains information that cannot be distributed, but may also contain information which contributes to the final version. In future implementations of the API, some of this information (authorship, metadata, etc...) may be made visible.
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