diff -r fd8751c3f3ee -r a721966779be doc/book/en/A03a-concepts.en.txt --- a/doc/book/en/A03a-concepts.en.txt Tue Apr 28 11:22:43 2009 +0200 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,536 +0,0 @@ -.. -*- coding: utf-8 -*- - -Concepts --------- - -This section aims to provide you the keys of success with `CubicWeb` -by clarifying the terms specific to our framework. - -Global architecture -~~~~~~~~~~~~~~~~~~~ -.. image:: images/archi_globale.en.png - - -`CubicWeb` framework is a server/client application framework. Those two -parts communicate through RQL (`CubicWeb` query language implementation) -and ResultSet (which will be explained in :ref:`TermsVocabulary`). - -The server manages all interactions with sources. - - -.. note:: - Usually, the client and server sides are integrated in the same - process and interact directly, without the need for distant - calls using Pyro. But, it is important to note that those two - sides, client/server, are disjointed and it is possible to execute - a couple of calls in distinct processes to balance the load of - your web site on one or more machines. - -.. _TermsVocabulary: - -Terms and vocabulary -~~~~~~~~~~~~~~~~~~~~~ - -`CubicWeb` defines its own terminology. To make sure there is no confusion -while reading this book, we strongly recommand you take time to go through -the following definitions that are the basics to understand while -developing with `CubicWeb`. - -*schema* - The schema defines the data model of an application based on entities - and relations, modeled with a comprehensive language made of Python - classes based on `yams`_ library. This is the core piece - of an application. It is initially defined in the file system and is - stored in the database at the time an instance is created. `CubicWeb` - provides a certain number of system entities included automatically - (necessary for the core of `CubicWeb`) and a library of - cubes (which defined application entities) that can be explicitely - included if necessary. - -*entity type* - An entity type is a set of attributes; the essential attribute of - an entity is its key, named eid. - -*relation type* - Entities are linked to each others by relations. In `CubicWeb` - relations are binary: by convention we name the first item of - a relation the `subject` and the second the `object`. - -*final entity type* - Final types correspond to the basic types such as string of characters, - integers... Those types have a main property which is that they can - only be used as `object` of a relation. The attributes of an entity - (non final) are entities (finals). - -*final relation type* - A relation is said final if its `object` is a final type. This is equivalent - to an entity attribute. - -*relation definition* - A relation definition is a 3-uple (subject entity type, relation type, object - entity type), with an associated set of property such as cardinality, constraints... - -*repository* - This is the RQL server side of `CubicWeb`. Be carefull not to get - confused with a Mercurial repository or a debian repository. - -*source* - A data source is a container of data (SGBD, LDAP directory, `Google - App Engine`'s datastore ...) integrated in the - `CubicWeb` repository. This repository has at least one source, `system` which - contains the schema of the application, plain-text index and other - vital informations for the system. - -*configuration* - It is possible to create different configurations for an instance: - - - ``repository`` : repository only, accessible for clients using Pyro - - ``twisted`` : web interface only, access the repository using Pyro - - ``all-in-one`` : web interface and repository in a single process. - The repository could be or not accessible using Pyro. - -*cube* - A cube is a model grouping one or multiple data types and/or views - to provide a specific functionality or a complete `CubicWeb` application - potentially using other cubes. The available cubes are located in the file - system at `/path/to/forest/cubicweb/cubes` for a Mercurial forest installation. - For a debian packages installation they will be located in - `/usr/share/cubicweb/cubes`. - Larger applications can be built quite fast by importing cubes, - adding entities and relationships, overriding the - *views* that display the cubes or by editing informations not provided by - the cubes. - -*instance* - An instance is a specific installation of one or multiple cubes. All the required - configuration files necessary for the well being of your web application - are grouped in an instance. This will refer to the cube(s) your application - is based on. - For example logilab.org and our intranet are two instances of a single - cube "jpl", developped internally. - The instances are defined in the directory `/etc/cubicweb.d`. - -*application* - The term application is sometimes used to talk about an instance - and sometimes to talk of a cube depending on the context. - So we would like to avoid using this term and try to use *cube* and - *instance* instead. - -*result set* - This object contains the results of an RQL query sent to the source - and informations on the query. - -*Pyro* - `Python Remote Object`_, distributed objects system similar to Java's RMI - (Remote Method Invocation), which can be used for the dialog between the web - side of the framework and the RQL repository. - -*query language* - A full-blown query language named RQL is used to formulate requests - to the database or any sources such as LDAP or `Google App Engine`'s - datastore. - -*views* - A view is applied to a `result set` to present it as HTML, XML, - JSON, CSV, etc. Views are implemented as Python classes. There is no - templating language. - -*generated user interface* - A user interface is generated on-the-fly from the schema definition: - entities can be created, displayed, updated and deleted. As display - views are not very fancy, it is usually necessary to develop your - own. Any generated view can be overridden by defining a new one with - the same identifier. - -*rql* - Relation Query Language in order to emphasize the way of browsing relations. - This query language is inspired by SQL but is on a higher level; - its implementation generates SQL. - - -.. _`Python Remote Object`: http://pyro.sourceforge.net/ -.. _`yams`: http://www.logilab.org/project/yams/ - - -`CubicWeb` engine -~~~~~~~~~~~~~~~~~ - -The engine in `CubicWeb` is a set of classes managing a set of objects loaded -dynamically at the startup of `CubicWeb` (*appobjects*). Those dynamic objects, -based on the schema or the library, are building the final application. -The different dynamic components are for example: - -* client and server side - - - entities definition, containing the logic which enables application data manipulation - -* client side - - - *views*, or more specifically - - - boxes - - header and footer - - forms - - page templates - - - *actions* - - *controllers* - -* server side - - - notification hooks - - notification views - -The components of the engine are: - -* a frontal web (only twisted is available so far), transparent for dynamic objects -* an object that encapsulates the configuration -* a `registry` (`cubicweb.cwvreg`) containing the dynamic objects loaded automatically - -Every *appobject* may access to the instance configuration using its *config* attribute -and to the registry using its *vreg* attribute. - -API Python/RQL -~~~~~~~~~~~~~~ - -The Python API developped to interface with RQL is inspired from the standard db-api, -with a Connection object having the methods cursor, rollback and commit essentially. -The most important method is the `execute` method of a cursor : - -`execute(rqlstring, args=None, eid_key=None, build_descr=True)` - -:rqlstring: the RQL query to execute (unicode) -:args: if the query contains substitutions, a dictionary containing the values to use -:eid_key: - an implementation detail of the RQL cache implies that if a substitution - is used to introduce an eid *susceptible to raise the ambiguities in the query - type resolution*, then we have to specify the corresponding key in the dictionary - through this argument - - -The `Connection` object owns the methods `commit` and `rollback`. You *should -never need to use them* during the development of the web interface based on -the `CubicWeb` framework as it determines the end of the transaction depending -on the query execution success. - -.. note:: - While executing update queries (SET, INSERT, DELETE), if a query generates - an error related to security, a rollback is automatically done on the current - transaction. - - -The `Request` class (`cubicweb.web`) -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -A request instance is created when an HTTP request is sent to the web server. -It contains informations such as form parameters, user authenticated, etc. - -**Globally, a request represents a user query, either through HTTP or not -(we also talk about RQL queries on the server side for example).** - -An instance of `Request` has the following attributes: - -* `user`, instance of `cubicweb.common.utils.User` corresponding to the authenticated - user -* `form`, dictionary containing the values of a web form -* `encoding`, character encoding to use in the response - -But also: - -:Session data handling: - * `session_data()`, returns a dictionary containing all the session data - * `get_session_data(key, default=None)`, returns a value associated to the given - key or the value `default` if the key is not defined - * `set_session_data(key, value)`, assign a value to a key - * `del_session_data(key)`, suppress the value associated to a key - - -:Cookies handling: - * `get_cookie()`, returns a dictionary containing the value of the header - HTTP 'Cookie' - * `set_cookie(cookie, key, maxage=300)`, adds a header HTTP `Set-Cookie`, - with a minimal 5 minutes length of duration by default (`maxage` = None - returns a *session* cookie which will expire when the user closes the browser - window) - * `remove_cookie(cookie, key)`, forces a value to expire - -:URL handling: - * `url()`, returns the full URL of the HTTP request - * `base_url()`, returns the root URL of the web application - * `relative_path()`, returns the relative path of the request - -:And more...: - * `set_content_type(content_type, filename=None)`, adds the header HTTP - 'Content-Type' - * `get_header(header)`, returns the value associated to an arbitrary header - of the HTTP request - * `set_header(header, value)`, adds an arbitrary header in the response - * `cursor()` returns a RQL cursor on the session - * `execute(*args, **kwargs)`, shortcut to ``.cursor().execute()`` - * `property_value(key)`, properties management (`CWProperty`) - * dictionary `data` to store data to share informations between components - *while a request is executed* - -Please note that this class is abstract and that a concrete implementation -will be provided by the *frontend* web used (in particular *twisted* as of -today). For the views or others that are executed on the server side, -most of the interface of `Request` is defined in the session associated -to the client. - -The `AppObject` class -~~~~~~~~~~~~~~~~~~~~~ - -In general: - -* we do not inherit directly from this class but from a more specific - class such as `AnyEntity`, `EntityView`, `AnyRsetView`, - `Action`... - -* to be recordable, a subclass has to define its own register (attribute - `__registry__`) and its identifier (attribute `id`). Usually we do not have - to take care of the register, only the identifier `id`. - -We can find a certain number of attributes and methods defined in this class -and common to all the application objects. - -At the recording, the following attributes are dynamically added to -the *subclasses*: - -* `vreg`, the `vregistry` of the application -* `schema`, the application schema -* `config`, the application configuration - -We also find on instances, the following attributes: - -* `req`, `Request` instance -* `rset`, the *result set* associated to the object if necessary -* `cursor`, rql cursor on the session - - -:URL handling: - * `build_url(method=None, **kwargs)`, returns an absolute URL based on - the given arguments. The *controller* supposed to handle the response, - can be specified through the special parameter `method` (the connection - is theoretically done automatically :). - - * `datadir_url()`, returns the directory of the application data - (contains static files such as images, css, js...) - - * `base_url()`, shortcut to `req.base_url()` - - * `url_quote(value)`, version *unicode safe* of the function `urllib.quote` - -:Data manipulation: - - * `etype_rset(etype, size=1)`, shortcut to `vreg.etype_rset()` - - * `eid_rset(eid, rql=None, descr=True)`, returns a *result set* object for - the given eid - * `entity(row, col=0)`, returns the entity corresponding to the data position - in the *result set* associated to the object - - * `complete_entity(row, col=0, skip_bytes=True)`, is equivalent to `entity` but - also call the method `complete()` on the entity before returning it - -:Data formatting: - * `format_date(date, date_format=None, time=False)` returns a string for a - mx date time according to application's configuration - * `format_time(time)` returns a string for a mx date time according to - application's configuration - -:And more...: - - * `external_resource(rid, default=_MARKER)`, access to a value defined in the - configuration file `external_resource` - - * `tal_render(template, variables)`, renders a precompiled page template with - variables in the given dictionary as context - -.. note:: - When we inherit from `AppObject` (even not directly), you *always* have to use - **super()** to get the methods and attributes of the superclasses, and not - use the class identifier. - For example, instead of writting: :: - - class Truc(PrimaryView): - def f(self, arg1): - PrimaryView.f(self, arg1) - - You'd better write: :: - - class Truc(PrimaryView): - def f(self, arg1): - super(Truc, self).f(arg1) - -.. _cubesConcepts: - -Cubes -~~~~~ - -What is a cube ? -```````````````` - -A cube is a model grouping one or more entity types and/or views associated -in order to provide a specific feature or even a complete application using -other cubes. - -You can decide to write your own set of cubes if you wish to re-use the -entity types you develop. Lots of cubes are available from the `CubicWeb -Forge`_ under a free software license. - -.. _`CubicWeb Forge`: http://www.cubicweb.org/project/ - -.. _foundationsCube: - -Standard structure for a cube -````````````````````````````` - -A cube is structured as follows: - -:: - - mycube/ - | - |-- data/ - | |-- cubes.mycube.css - | |-- cubes.mycube.js - | `-- external_resources - | - |-- debian/ - | |-- changelog - | |-- compat - | |-- control - | |-- copyright - | |-- cubicweb-mycube.prerm - | `-- rules - | - |-- entities.py - | - |-- i18n/ - | |-- en.po - | `-- fr.po - | - |-- __init__.py - | - |-- MANIFEST.in - | - |-- migration/ - | |-- postcreate.py - | `-- precreate.py - | - |-- __pkginfo__.py - | - |-- schema.py - | - |-- setup.py - | - |-- site_cubicweb.py - | - |-- hooks.py - | - |-- test/ - | |-- data/ - | | `-- bootstrap_cubes - | |-- pytestconf.py - | |-- realdb_test_mycube.py - | `-- test_mycube.py - | - `-- views.py - - -We can use subpackages instead of python modules for ``views.py``, ``entities.py``, -``schema.py`` or ``hooks.py``. For example, we could have: - -:: - - mycube/ - | - |-- entities.py - |-- hooks.py - `-- views/ - |-- forms.py - |-- primary.py - `-- widgets.py - - -where : - -* ``schema`` contains the schema definition (server side only) -* ``entities`` contains the entities definition (server side and web interface) -* ``sobjects`` contains hooks and/or views notifications (server side only) -* ``views`` contains the web interface components (web interface only) -* ``test`` contains tests related to the application (not installed) -* ``i18n`` contains message catalogs for supported languages (server side and - web interface) -* ``data`` contains data files for static content (images, css, javascripts) - ...(web interface only) -* ``migration`` contains initialization file for new instances (``postcreate.py``) - and a file containing dependencies of the component depending on the version - (``depends.map``) -* ``debian`` contains all the files managing debian packaging (you will find - the usual files ``control``, ``rules``, ``changelog``... not installed) -* file ``__pkginfo__.py`` provides component meta-data, especially the distribution - and the current version (server side and web interface) or sub-cubes used by - the cube. - - -At least you should have: - -* the file ``__pkginfo__.py`` -* the schema definition - XXX false, we may want to have cubes which are only adding a service, - no persistent data (eg embedding for instance) - - -Standard library -```````````````` - -A library of standard cubes are available from `CubicWeb Forge`_ -Cubes provide entities and views. - -The available application entities are: - -* addressbook_: PhoneNumber and PostalAddress - -* basket_: Basket (like a shopping cart) - -* blog_: Blog (a *very* basic blog) - -* comment_: Comment (to attach comment threads to entities) - -* event_: Event (define events, display them in calendars) - -* file_: File (to allow users to upload and store binary or text files) - -* folder_: Folder (to organize things but grouping them in folders) - -* keyword_: Keyword (to define classification schemes) - -* link_: Link (to collect links to web resources) - -* mailinglist_: MailingList (to reference a mailing-list and the URLs - for its archives and its admin interface) - -* person_: Person (easily mixed with addressbook) - -* tag_: Tag (to tag anything) - -* task_: Task (something to be done between start and stop date) - -* zone_: Zone (to define places within larger places, for example a - city in a state in a country) - -.. _addressbook: http://www.cubicweb.org/project/cubicweb-addressbook -.. _basket: http://www.cubicweb.org/project/cubicweb-basket -.. _blog: http://www.cubicweb.org/project/cubicweb-blog -.. _comment: http://www.cubicweb.org/project/cubicweb-comment -.. _event: http://www.cubicweb.org/project/cubicweb-event -.. _file: http://www.cubicweb.org/project/cubicweb-file -.. _folder: http://www.cubicweb.org/project/cubicweb-folder -.. _keyword: http://www.cubicweb.org/project/cubicweb-keyword -.. _link: http://www.cubicweb.org/project/cubicweb-link -.. _mailinglist: http://www.cubicweb.org/project/cubicweb-mailinglist -.. _person: http://www.cubicweb.org/project/cubicweb-person -.. _tag: http://www.cubicweb.org/project/cubicweb-tag -.. _task: http://www.cubicweb.org/project/cubicweb-task -.. _zone: http://www.cubicweb.org/project/cubicweb-zone