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RENCI Geoanalytics - Dynamic model infrastructure

To facilitate a "push-to-publish" model of data publishing, RENCI's Geoanalytics introduces "dynamic models" to Django. Dynamic models allow you to build forms and views that will allow a user to upload data in a controlled fashion. This data will then populate a database table or series of tables in the ORM. Models will be generated and these models will be automagically exposed to the Admin interface and can be added dynamically to RESTful APIs as well through Tastypie.

In the near future, you will also be able to expose these models via WFS and WMS using Geoanalytics OWS services.

Requirements beyond basic Django

ga_dynamic_models requires a version of pymongo on your system and a writable MongoDB instance, as dynamic models are stored in MongoDB as documents.

Once you have this, add lines to your settings.py file like this:

MONGODB_CONNECTIONS = {
    'default' : pymongo.Connection()
}

MONGODB_ROUTES = {
    'default' : MONGODB_CONNECTIONS['default']['default_collection']  # CONNECTIONS['connection']['database']
    'ga_dynamic_models : MONGODB_CONNECTIONS['default']['ga_dynamic_models']
}

These are used by other apps as well, and effectively create a routing mechanism for connections that use the raw pymongo driver. The values in MONGODB_ROUTES can change depending on your particular database configuration. If ga_dynamic_models is listed as a route in the settings, then this app will use that route, otherwise it will use

the default route and create two new collections, ga_dynamic_models__models and ga_dynamic_models__apis.

Getting started

This app is still very early in its development stage. Although it is working, parts of the application regarding management are currently lacking. Currently there are no management views setup for this application. Furthermore there are no default forms setup for creating dynamic models. There will be soon, but for now this application seems useful and generic enough to make available.

Once you have fulfilled the main requirements, add ga_dynamic_models to your INSTALLED_APPS section in Django's settings, and add an entry for ga_dynamic_models.urls in your main urls.py. This will create an endpoint at ^/api/ga_dynamic_models that will build out as more dynamic models are added. See the django tastypie documentation for more details on how Tastypie RESTful APIs work. They are largely compatible with popular client-side libraries like jQuery, jQueryMobile, ExtJS4, and Sencha Touch.

Creating a model

The only way to create a model right now is in Python code. The module ga_dynamic_models.utils contains tools to help you do this. The simplest way is to use the declare_model function and the simple_(geo)model function like so:

from ga_dynamic_models.utils import *

Then declare a new geographic model:

declare_model(simple_geomodel('MyGeoModel',
    geom = simple_geofield('PointField'),
    some_name = simple_geofield('CharField', max_length=255, default='', null=True, db_index=True),
    some_integer = simple_geofield("IntegerField", default=10)
))

Or declare a new regular model:

declare_model(simple_model("MyRegularModel",
    some_name = simple_field('CharField', max_length=255, default='', null=True, db_index=True),
    some_integer = simple_field("IntegerField", default=10)
))

Then if you want to expose these as RESTful services via Tastypie, you can do this:

declare_resource(simple_model_resource(
    'ga_dynamic_models.models',
    'MyRegularModel',
    "my_regular_model"
))

declare_resource(simple_geo_resource(
    'ga_dynamic_models.models',
    'MyGeoModel',
    'my_geo_model'
))

The declare_model function adds a new model to the list. Note this does NOT create any tables in your main database. To do that, you MUST run the syncdb task yourself, or achieve this in code. It does however, expose the model to the Admin interface, if you have enabled the admin application.

The declare_resource function adds a model to the API. See the utils module for more details on how these functions work and the Django model Meta options and Tastypie Meta options pages on what extra meta options can be passed to these functions. More documentation will be forthcoming on this module, but for now you're kind of going to be stuck reading the code a bit. Check the tests.py file for examples of usage.

Support

Please post issues at github's repository for ga_dynamic_models for support.

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