ModelViewController.wiki - wiki - Git at Google

 #summary Model-View-Controller pattern
 #labels Phase-Design,Deprecated,Importance-Overview

 [MelangeIntro Melange] follows
 [http://en.wikipedia.org/wiki/Model-view-controller Model-View-Controller] patterns
 at multiple levels.  The [SoCOverview SoC framework] provides a set of
 common [ModelsOverview Model], [ViewsOverview Views], and
 [ControllersOverview generic Controllers] to be used by each Melange
 web application.  Each of those applications is then similarly arranged
 in a Model-View-Controller pattern.

 == Models ==

 Entities of each [ModelsOverview Model] are stored in the
 [http://code.google.com/appengine/docs/datastore/ Google App Engine Datastore].  All
 data for a given instance of a particular Program is stored in Model entities
 in the Datastore.  The SoC framework Models are designed so that they can be
 used in a variety of Program formats, including both [GSoC GSoC] and
 [GHOP GHOP].  Other Melange Models not in the SoC framework are specific to
 a particular Program.

 The Models are also designed so that, while entities are specific to a given
 year of a particular Program, entities can be _imported_ from one Program
 instance to another.  For example, a [PersonModel Person] need not re-enter
 all of their personal information to participate in another, future Program,
 even if their participation is going to be in a different role (an
 [OrganizationModel Organization] [ReviewerModel Reviewer], say, rather than
 a [ContributorModel Contributor]).

 == Views ==

 Model entities are displayed and modified via a variety of
 [ViewsOverview Views].  Some views simply display entities or lists of
 entities, while other views are forms for creating and altering entities.
 The Melange views are implemented using Django templates and forms.
 Many of these views are shared and re-used between different Programs and
 their Program-specific [ControllersOverview Controllers].

 === Import and Export Views ===

 In addition to the HTML page views, other special "Views" are used to provide
 read-write [GDataOverview GData APIs] and read-only [FeedsOverview Atom feeds]
 and CSV file exports.  These GData APIs, Atom feeds, and CSV files provide
 import and export capabilities for Program entities.

 The Melange GData APIs will also make it possible to implement alternative
 front-ends capable of viewing and manipulating, say, one Organization's data.
 Such a front-end could be implemented in any programming language that can be
 used to implement a GData client.  Such Organization-specific front-ends could,
 for example, be embedded in the Organization's web site.  These GData APIs
 could also be used to create widgets such as
 [http://code.google.com/apis/gadgets/ Google Gadgets] that monitor or alter small
 aspects of a Program.

 Atom feeds make it possible to monitor activity during the course of a
 Program *without* resorting to email, using a _pull_ approach instead of the
 existing email _push_ method.

 == Controllers ==

 Each separate program (e.g. [GSoC GSoC] and [GHOP GHOP]) implements its own
 [ControllersOverview Controller] containing the "business logic" of the
 program (though in the case of these two examples, much of the code in the
 two Controllers is expected to be shared).  It will be possible to support
 Program formats that have not yet been conceived by adding new Controller
 modules to the framework.  Since Melange is being released under an Open Source
 license, new Sponsor organizations could implement their own custom Program
 while reusing much of the SoC framework code.

 === Security and Roles ===

 The Controllers make use of [UserRoles user role] [RoleModels Model entities]
 to decide what other Program entities are viewable or modifiable by a
 particular
 [http://www.google.com/support/accounts/ Google Accounts-authenticated]
 [UserModel User].

 [ViewsOverview Views] will submit the Model entity and the
 [UserRoles specific role] to an "authorization" method in the Controller.
 This method will indicate what privileges (read-only, read-write,
 not-authorized, etc.) that specific User in that specific Role has for
 that specific Model entity.  These authorization methods in the Controller
 can also provide error indications and descriptive text that can be
 displayed to the User by the View.


 ----
 _Copyright 2008 Google Inc._
 _This work is licensed under a_
 [http://soc.googlecode.com/svn/wiki/html/licenses/cc-by-attribution-2_5.html Creative Commons Attribution 2.5 License].
 [http://creativecommons.org/licenses/by/2.5/ http://soc.googlecode.com/svn/wiki/html/licenses/cc-by-2_5-88x31.png]
	#summary Model-View-Controller pattern
	#labels Phase-Design,Deprecated,Importance-Overview

	[MelangeIntro Melange] follows
	[http://en.wikipedia.org/wiki/Model-view-controller Model-View-Controller] patterns
	at multiple levels. The [SoCOverview SoC framework] provides a set of
	common [ModelsOverview Model], [ViewsOverview Views], and
	[ControllersOverview generic Controllers] to be used by each Melange
	web application. Each of those applications is then similarly arranged
	in a Model-View-Controller pattern.

	== Models ==

	Entities of each [ModelsOverview Model] are stored in the
	[http://code.google.com/appengine/docs/datastore/ Google App Engine Datastore]. All
	data for a given instance of a particular Program is stored in Model entities
	in the Datastore. The SoC framework Models are designed so that they can be
	used in a variety of Program formats, including both [GSoC GSoC] and
	[GHOP GHOP]. Other Melange Models not in the SoC framework are specific to
	a particular Program.

	The Models are also designed so that, while entities are specific to a given
	year of a particular Program, entities can be _imported_ from one Program
	instance to another. For example, a [PersonModel Person] need not re-enter
	all of their personal information to participate in another, future Program,
	even if their participation is going to be in a different role (an
	[OrganizationModel Organization] [ReviewerModel Reviewer], say, rather than
	a [ContributorModel Contributor]).

	== Views ==

	Model entities are displayed and modified via a variety of
	[ViewsOverview Views]. Some views simply display entities or lists of
	entities, while other views are forms for creating and altering entities.
	The Melange views are implemented using Django templates and forms.
	Many of these views are shared and re-used between different Programs and
	their Program-specific [ControllersOverview Controllers].

	=== Import and Export Views ===

	In addition to the HTML page views, other special "Views" are used to provide
	read-write [GDataOverview GData APIs] and read-only [FeedsOverview Atom feeds]
	and CSV file exports. These GData APIs, Atom feeds, and CSV files provide
	import and export capabilities for Program entities.

	The Melange GData APIs will also make it possible to implement alternative
	front-ends capable of viewing and manipulating, say, one Organization's data.
	Such a front-end could be implemented in any programming language that can be
	used to implement a GData client. Such Organization-specific front-ends could,
	for example, be embedded in the Organization's web site. These GData APIs
	could also be used to create widgets such as
	[http://code.google.com/apis/gadgets/ Google Gadgets] that monitor or alter small
	aspects of a Program.

	Atom feeds make it possible to monitor activity during the course of a
	Program without resorting to email, using a _pull_ approach instead of the
	existing email _push_ method.

	== Controllers ==

	Each separate program (e.g. [GSoC GSoC] and [GHOP GHOP]) implements its own
	[ControllersOverview Controller] containing the "business logic" of the
	program (though in the case of these two examples, much of the code in the
	two Controllers is expected to be shared). It will be possible to support
	Program formats that have not yet been conceived by adding new Controller
	modules to the framework. Since Melange is being released under an Open Source
	license, new Sponsor organizations could implement their own custom Program
	while reusing much of the SoC framework code.

	=== Security and Roles ===

	The Controllers make use of [UserRoles user role] [RoleModels Model entities]
	to decide what other Program entities are viewable or modifiable by a
	particular
	[http://www.google.com/support/accounts/ Google Accounts-authenticated]
	[UserModel User].

	[ViewsOverview Views] will submit the Model entity and the
	[UserRoles specific role] to an "authorization" method in the Controller.
	This method will indicate what privileges (read-only, read-write,
	not-authorized, etc.) that specific User in that specific Role has for
	that specific Model entity. These authorization methods in the Controller
	can also provide error indications and descriptive text that can be
	displayed to the User by the View.


	----
	_Copyright 2008 Google Inc._
	_This work is licensed under a_
	[http://soc.googlecode.com/svn/wiki/html/licenses/cc-by-attribution-2_5.html Creative Commons Attribution 2.5 License].
	[http://creativecommons.org/licenses/by/2.5/ http://soc.googlecode.com/svn/wiki/html/licenses/cc-by-2_5-88x31.png]