Cartography

A low-level library that handles situations, their causal relationships, and the histories of both.

This library is a dependency of Causemap, which extends Cartography and adds other features.

Dependencies

• Access to a CouchDB
• Node.js

Installation

From source:

npm install

Then install the CouchDB design documents:

var cartography = require('cartography');
cartography.config.set({
  couchdb: {
    host: "http://username:password@localhost:5984",
    database: "cartography"
  }
});

cartography.install(console.log);

Testing

npm test

Example

var cartography = require('cartography');

var Situation = cartography.models.Situation;
var Relationship = cartography.models.Relationship;

cartography.config.set({
  couchdb: {
    host: "localhost",
    database: "cartography"
  }
});



var global_warming = new Situation();

global_warming.create(function(creation_error, creation_result){
  return console.log(creation_result);
});
// > { ok: true,
//   id: '514d5202e601ef23aa661e605d00599c',
//   rev: '1-e9d4bfdd8fed85f5b0f76875e5c877b8' }

global_warming.title('Global Warming', function(change_error, change_result){
  return console.log(change_result);
});
// > { ok: true,
//   id: '514d5202e601ef23aa661e605d005c6d',
//   rev: '1-e2daea3e47f3a04641f1c2e1d2f8b82c' }



var greenhouse_gasses = new Situation();

greenhouse_gasses.create(function(creation_error, creation_result){
  return console.log(creation_result);
});
// > { ok: true,
//   id: '514d5202e601ef23aa661e605d006adb',
//   rev: '1-656653eecb0375b75dbba2c1afde00c3' }

greenhoust_gasses.title('Greenhouse Gasses in the Atmosphere', function(
  change_error,
  change_result
){
  return console.log(change_result);
});
// > { ok: true,
//   id: '514d5202e601ef23aa661e605d006bb0',
//   rev: '1-6fc199d68bf98f4a383b7d02f77b4d50' }


greenhouse_gasses.caused(global_warming, function(
  relationship_error, 
  relationship_result
){
  return console.log(relationship_result);
});
// > { ok: true,
//   id: '514d5202e601ef23aa661e605d007452',
//   rev: '1-e21fb71c491a14822f96d894384adaec' }



// The `id` from the last operation is the id of the newly created
// relationship.
var greenhouse_gasses_cause_global_warming = new Relationship(
  '514d5202e601ef23aa661e605d007452'
);



greenhouse_gasses_cause_global_warming.summarize(console.log);
// > null { _id: '514d5202e601ef23aa661e605d007452',
//   _rev: '1-e21fb71c491a14822f96d894384adaec',
//   cause:
//    { _id: '514d5202e601ef23aa661e605d006adb',
//      title: 'Greenhouse Gasses in the Atmosphere',
//      location: undefined,
//      period: undefined,
//      alias: undefined },
//   effect:
//    { _id: '514d5202e601ef23aa661e605d00599c',
//      title: 'Global Warming',
//      location: undefined,
//      period: undefined,
//      alias: undefined },
//   revisable: true,
//   creation_date: 1384291766745,
//   immutable: true,
//   type: 'relationship' }

Tutorial

Configure the CouchDB host and database name for cartography to use:

var cartography = require('cartography');

cartography.config.set('couchdb', {
  host: 'http://username:passphrase@localhost:5984', 
  database: 'cartography'
});

Cartography configurations can be accessed using cartography.config.get from anywhere:

console.log(cartography.config.get('couchdb'));
// { host: 'http://username:passphrase@localhost:5984',
//   database: 'cartography' }

If you don't provide a key, get will return all configurations:

console.log(cartography.config.get());
// { couchdb:
//   { host: 'http://jeff:sbrooden@localhost:5984',
//     database: 'derp' } }

Now create a new Situation:

var Situation = cartography.models.Situation

var bitten_by_a_dog = new Situation();
bitten_by_a_dog.create(console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d00de52',
//   rev: '1-94825a79a389af9811646e79b7fcd92f' }

The new situation, bitten_by_a_dog has been saved to the couchdb database. Let's read it to see what we've got:

bitten_by_a_dog.read(console.log);
// > null { _id: '514d5202e601ef23aa661e605d00de52',
//   _rev: '1-94825a79a389af9811646e79b7fcd92f',
//   revisable: true,
//   creation_date: 1384457963498,
//   immutable: true,
//   type: 'situation' }

By passing console.log as the callback to read, we have all of the variables passed to it printed to the screen. The first argument value printed is null, which means that there was no error in reading the situation. Had there been one, the first argument passed to console.log would have been the error.

The second value printed by the callback is the new situation's document body. This object is interesting for the following reasons:

• It has properties generated by the database:
  • _id: CouchDB will add an _id to any document that doesn't have one already. By default, the _id generated by CouchDB is a UUID, which means that a new _id will never collide with an existing one.
  • _rev: a CouchDB document's revision number. This is used for keeping track of document versions in a distributed environment. It isn't used in this module, but it is essential for horizontal scaling.
• It has properties generated by Cartography:
  • type: All Cartography models have this field. Its value is a string representing indicating its type.
  • creation_date: Its value is the result of (new Date()).getTime(), or, the number of miliseconds since EPOCH at the time the document was first committed to the database.
  • immutable: No direct changes to the CouchDB document may be made. Where present in a Cartography-generated document, its value should be true as an indication that this document should not be updated in CouchdB directly. The reason for this is explained later.
  • revisable: This Cartography document should be changed incrementally. Change documents that refer to this one should be made to alter its fields and values.

Cartography is designed to maintain the history of Situation and Relationshipobjects. It does this by creating Change documents for each individual change that's made to a Situation or Relationship. Let's change our situation's title:

bitten_by_a_dog.title('I Was Bitten By a Doge', console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d00f458',
//   rev: '1-40877d02f7709abdbb49d10fc9a2973c' }

The id and rev returned in the callback as the result are the _id and _rev of the newly created Change document for our new situation's title. Let's have a see at what the new Change looks like in the database:

var Change = cartography.models.Change;

var new_title = new Change('514d5202e601ef23aa661e605d00f458');
new_title.read(console.log);
// > null { _id: '514d5202e601ef23aa661e605d00f458',
//   _rev: '1-40877d02f7709abdbb49d10fc9a2973c',
//   changed:
//    { doc: { _id: '514d5202e601ef23aa661e605d00de52', type: 'situation' },
//      field: { name: 'title', to: 'I Was Bitten by a Doge' } },
//   creation_date: 1384490982792,
//   immutable: true,
//   type: 'change' }

The Change document contains many of the same fields we saw in the Situation document, though there are some differences:

• A Change document is immutable, but not revisable. This means that once the change is stored, it cannot be updated in CouchDB, and it cannot be revised by creating other Change documents.
• It has a field called changed which contains details about the revisable doc that was changed, what the field's name is, and what its value in that document was changed to.

Let's check the situation, now that we've set its title with this Change:

bitten_by_a_dog.read(console.log);
// > null { _id: '514d5202e601ef23aa661e605d00de52',
//   _rev: '1-94825a79a389af9811646e79b7fcd92f',
//   revisable: true,
//   creation_date: 1384457963498,
//   immutable: true,
//   type: 'situation',
//   title: 'I Was Bitten by a Doge' }

Great. We see the change we made with bitten_by_a_dog.title reflected in the Cartography document, but there appears to be a typo: "Doge" should be "Dog". Let's correct it:

bitten_by_a_dog.title("I Was Bitten by a Dog", console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d00f9a1',
//   rev: '1-0c1b87fd1d9892479222c671b7f9c6f5' }

bitten_by_a_dog.read(console.log);
// > null { _id: '514d5202e601ef23aa661e605d00de52',
//   _rev: '1-94825a79a389af9811646e79b7fcd92f',
//   revisable: true,
//   creation_date: 1384457963498,
//   immutable: true,
//   type: 'situation',
//   title: 'I Was Bitten by a Dog' }

The title is now typo-free. Cartography uses the power of CouchDB's views to get the latest changes to a revisable document, such as a Situation, then builds the composite that is returned by the read method. Wow.

Add some details and a description:

bitten_by_a_dog.period('Friday November 15th at 11am', console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d00fbd6',
//   rev: '1-ff3a2e8a90d90499a835d056084fb5a6' }

bitten_by_a_doc.location('Montreal, QC', console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d0107ec',
//   rev: '1-95604fdb1879edd9f787925ae388f17e' }

bitten_by_a_dog.description(
  "This stupid dog bit me.", 
  console.log
)
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d010a49',
//   rev: '1-b3cae7a25fcf99ab51fe1891c1fc42cf' }

bitten_by_a_dog.read(console.log)
// > null { _id: '514d5202e601ef23aa661e605d00de52',
//   _rev: '1-94825a79a389af9811646e79b7fcd92f',
//   revisable: true,
//   creation_date: 1384457963498,
//   immutable: true,
//   type: 'situation',
//   description: 'This stupid dog bit me.',
//   location: 'Montreal, QC',
//   period: 'Friday November 15th at 11am',
//   title: 'I Was Bitten by a Dog' }

But what caused this situation? The cause for the Situation bitten_by_a_dog is of course, another situation:

var ate_dogs_food = new Situation();

ate_dogs_food.create(console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d011860',
//   rev: '1-fa9983ebf1c6749133c00e9a1a264706' }

ate_dogs_food.title("I Ate Some Dog's Food", console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d011cb7',
//   rev: '1-450587c4b93e053b92bd5ac487ea07b5' }

Now that the Situation ate_dogs_food has been stored, it can be set as a cause for bitten_by_a_dog:

bitten_by_dog.because(ate_dogs_food, console.log);
// > null { ok: true,
//   id: '514d5202e601ef23aa661e605d011e0e',
//   rev: '1-ad947efac4b06b9ded8d8ac5f2aa38cc' }

The response from the because method contains the id and rev of the newly created Relationship document:

var Relationship = cartography.models.Relationship;

var bitten_by_dog_because_i_ate_its_food = new Relationship(
  '514d5202e601ef23aa661e605d011e0e'
)

bitten_by_dog_because_i_ate_its_food.read(console.log);
// > null { _id: '514d5202e601ef23aa661e605d011e0e',
//   _rev: '1-ad947efac4b06b9ded8d8ac5f2aa38cc',
//   cause: { _id: '514d5202e601ef23aa661e605d011860' },
//   effect: { _id: '514d5202e601ef23aa661e605d00de52' },
//   revisable: true,
//   creation_date: 1384546572729,
//   immutable: true,
//   type: 'relationship' }

This is the result of a read operation on a Relationship. Here is what's new:

• cause and effect fields contain an object with an _id corresponding to the Situation documents that are the cause and effect in the relationship.

This Relationship can be seen in the results of the bitten_by_a_dog.causes:

bitten_by_a_dog.causes(console.log);
// > null [ { _id: '514d5202e601ef23aa661e605d011e0e',
//     _rev: '1-ad947efac4b06b9ded8d8ac5f2aa38cc',
//     cause: { _id: '514d5202e601ef23aa661e605d011860' },
//     effect: { _id: '514d5202e601ef23aa661e605d00de52' },
//     revisable: true,
//     creation_date: 1384546572729,
//     immutable: true,
//     type: 'relationship' } ]

The same results can be seen with ate_dogs_food.effects.

Purpose

The purpose of this module is to provide a low-level interface for manipulating Causemap objects; Situations, Relationships and their changes.

Objectives

• Provide the ability to create, read, update and delete (CRUD) the following basic Causemap structures:
  • Situations
  • Relationships
• Keep history: keep a history of all changes to Situations and Relationships. This is so that changes can be reviewed and disputed if necessary. No data regarding Situations or Relationships should ever be truly lost unless either of them are explicitely deleted.

License

Copyright © 2013 Classy Applications

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.