Places:Design Overview: Difference between revisions

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= Design Overview =
= Design Overview =
Places is designed to be a robust back-end for Bookmarks, History and related components using the mozStorage wrapper for SQLite. It is intended to provide useful APIs for a more usable front-end, emphasizing simple search and categorization.
Generally, you'll want to look at the [https://developer.mozilla.org/En/Places documentation on MDC] instead of what is here.  The documentation here is only internal API documentation that isn't generally exposed to add-on authors.
Related Documents:
* [[Places:AutoComplete]]
* [[Places:Drag & Drop]]
* [[Places:Live Bookmarks]]


== Objectives ==
== Objectives ==


The primary objectives:
* Improve access to History and Bookmarks
* Make it easier for people to Bookmark pages
Secondary objectives:
* Consolidating user data formats
* Providing a platform for using interesting per-URL metadata
* Improving the capabilities of Live Bookmarks
* Providing a solid architecture for bookmark sync and remote storage
* Extensible Bookmark Providers for customization
* Extensible Bookmark Providers for customization
* Flexible Query System
* Flexible Query System
* Clean Architecture for ease of code reuse and maintainability
* Clean Architecture for ease of code reuse and maintainability


== Front End Architecture ==
The Front End Architecture utilizes a MVC (model-view-controller) design. This calls for clean separation between each of the three components. The benefits of this approach are improved maintainability, stability and extensibility.
Within the Places code, the Model can be considered to be the SQL tables
and the code that creates them, the query system to access them, and the
simple manipulation pathways provided through services like
nsINavHistoryService and nsINavBookmarksService.
The View is the piece that displays information from the Model in one
way or another. In code, these are menu.xml, toolbar.xml and tree.xml.


The Controller is the piece that interprets user actions on a selection
== Background ==
and carries them out - basically linking the Model and the View. In
code, this is controller.js.


The extent to which these services are kept independent can be seen in the following details:
Studies from the late 1990s show that while revisitations of pages previously seen counted for roughly 39% of all page navigations (see [http://scholar.google.com/ Google Scholar]), Bookmarks and History usage was low (1-3%), despite the fact that roughly 20% of those revisitations were to pages seen > 10 URLs ago (and thus outside the usefulness range of the Back button or menu).  
* The Model does not in general deal with presentation.
* The Controller knows of "selection" only as a concept abstract from the details of the selected View (e.g. a complex tree selection versus a selected toolbar button or menu item). As far as the Controller is concerned, the selection is a list of Result Nodes, there are no View-specific selection ranges, etc.
* The Views know nothing about the functions performed when the user interacts with their content, since that is instance specific. The Views implement a View Interface which handle translating their unique selection characteristics into an agnostic form the Controller can deal with.


The idea is that someone can instantiate a View, attach a Controller, and define the behavioral characteristics that suit their use, in very little code. Examples:
Autocomplete in the URL bar is a useful tool but fails to address some common desires when looking up visited pages. There is a gulf between the capabilities of that tool, the capabilities of the Bookmarks and History systems today, and the desired capabilities of those systems.


'''Bookmarks Menu'''
== Use Cases ==
* instantiate a Menu View, attached to the top level Browser Bookmarks Menu.
* attach the Controller
* attach a command event listener that handles user clicks in the menu
by loading the associated URL, if any, in a browser tab
* root the View on a Model query result, and tell it to populate itself


'''Folder Selector'''
* [[Places:History Use Cases]]
* instantiate a Menu View, attached to a menulist in the Places Search popup.
* [[Bookmarks Use Cases]] (not specific to places)
* attach the Controller
* attach a command event listener that handles user clicks in the menu by re-rooting a Tree View elsewhere in the UI
* root the View on a Model query result, and tell it to populate itself.


As you can see, this careful distinction between each allows us to rapidly build new user interface components by connecting the same Views and Controller with different application specific functionality.


<center>http://www.bengoodger.com/software/mb/places/MVC.png</center>


== Details ==
== Details ==
Line 55: Line 50:
http://people.mozilla.com/~dietrich/places-erd.png
http://people.mozilla.com/~dietrich/places-erd.png


Database schema complete with associations between the various tables within places.sqlite.
A detailed database schema complete with associations between the various tables within places.sqlite:
 
https://wiki.mozilla.org/images/d/d5/Places.sqlite.schema3.pdf
https://wiki.mozilla.org/images/d/d5/Places.sqlite.schema3.pdf
Schema for other sqlite files used by Firefox 3...
https://wiki.mozilla.org/images/4/43/Permissions.sqlite.schema.pdf<br>
https://wiki.mozilla.org/images/3/3d/Downloads.sqlite.schema.pdf<br>
https://wiki.mozilla.org/images/7/72/Content-prefs.sqlite.schema.pdf


Source code:  
Source code:  
Line 72: Line 60:
=== Views ===
=== Views ===


There are three primary types of view for Places:  
The [https://developer.mozilla.org/En/Displaying_Places_information_using_views MDC page] has the most up-to-date information on how to use views to display information from places.
 
* '''Tree/List view''' - Can show flat lists or hierarchical structures. e.g. the panes in the Places Organizer window.
* '''Toolbar view''' - Shows folders as buttons that have dropdown menus. e.g. the Bookmarks Toolbar in the browser window.
* '''Menu view''' - Shows folders as sub menus. e.g. the Bookmarks Menu in the browser window.
 
Each of these views implement a Places View interface which provides view-agnostic means for obtaining the current selection and other information. The Views themselves take on no controller-like responsibilities. They are not responsible for handling user clicks and opening links, etc - just presenting a list of places.  
 
XXXben - fill in details!


Source code: <code>mozilla/browser/components/places/content/tree|menu|toolbar.xml</code>
Source code: <code>mozilla/browser/components/places/content/tree|menu|toolbar.xml</code>
Line 92: Line 72:
== Querying History ==
== Querying History ==


<center>http://www.bengoodger.com/software/mb/places/LifeOfQuery.png</center>
See [https://developer.mozilla.org/En/Querying_Places the MDC page] for details on history querying.
 
To display results in a PlacesView, the following steps are performed:
 
=== Query Creation ===
 
Any list of items is the result of a query. e.g. the contents of a particular bookmark folder is a request for all URLs with the bookmark flag set that are contained by a named folder. Or all pages in a specific date range. And so on. Queries are represented as strings (which can be Bookmarked - "saved searches" or "virtual folders") containing all the parameters. -->brettw - fill in details!
 
=== Query Execution ===
 
The contents of the query string are deserialized and a series of Query objects are constructed. The query objects are executed.
 
=== Result Gathering ===
 
The results of the execution are gathered. --> brettw - fill in details! Not all queries produce results in the form of rows from the main URL table. Some produce results dynamically by consulting the contents of a directory on the user's file system (e.g. a new implementation of the old File System Datasource), for example. There are potentially other examples of remote data sources being used to feed data into the places view. Data sources like the Feed handler and the Bonjour listener would work slightly differently however. They would have their own timeout/notification based system by which they would detect new content, and then push URLs/rows into the main URL table whenever there was new data, so that when their containers were opened static content from the last dump is shown.
 
=== Result Organization ===
 
The results object is passed to a "Grouper" which organizes the results into a hierarchy based on a set of rules specified by the user interface. These rules form a kind of filter, for example: show all bookmarks organized into their appropriate folders; show history from last week, grouped by site; show all URLs matching the string "goats" in a flat, ungrouped list.
 
=== View Creation ===
 
The grouped results object is passed to the View implementation which supplies the necessary structure for the user interface.


== Other Components ==
== Other Components ==
Line 134: Line 92:
Migrating data from Netscape-bookmarks-file-1, [[Mork]], etc, to the storage format.  
Migrating data from Netscape-bookmarks-file-1, [[Mork]], etc, to the storage format.  


* [http://mxr.mozilla.org/seamonkey/source/browser/components/places/public/nsIPlacesImportExportService.idl HTML Import/Export API]
* [http://mxr.mozilla.org/mozilla-central/source/browser/components/places/public/nsIPlacesImportExportService.idl HTML Import/Export API]
* JSON Import/Export API (XXX {{bug|384370}})
* JSON Import/Export API (XXX {{bug|384370}})


Line 141: Line 99:
Observer APIs for extensions and other components that want to listen to backend activity:
Observer APIs for extensions and other components that want to listen to backend activity:


* [http://mxr.mozilla.org/seamonkey/source/toolkit/components/places/public/nsINavBookmarksService.idl#56 Bookmark Observer API]
* [https://developer.mozilla.org/En/NsINavBookmarkObserver Bookmark Observer API]
* [http://mxr.mozilla.org/seamonkey/source/toolkit/components/places/public/nsINavHistoryService.idl#703 History Observer API]
* [https://developer.mozilla.org/En/NsINavHistoryObserver History Observer API]
 
 
=== Historical Documents ===
 
This documents are kept around for historical purposes only.
 
* [[Places:User_Interface]]
* [[Browser History]]
* [[Places:Manager]]

Latest revision as of 22:27, 29 January 2009

Design Overview

Places is designed to be a robust back-end for Bookmarks, History and related components using the mozStorage wrapper for SQLite. It is intended to provide useful APIs for a more usable front-end, emphasizing simple search and categorization.

Generally, you'll want to look at the documentation on MDC instead of what is here. The documentation here is only internal API documentation that isn't generally exposed to add-on authors.

Related Documents:

Objectives

The primary objectives:

  • Improve access to History and Bookmarks
  • Make it easier for people to Bookmark pages

Secondary objectives:

  • Consolidating user data formats
  • Providing a platform for using interesting per-URL metadata
  • Improving the capabilities of Live Bookmarks
  • Providing a solid architecture for bookmark sync and remote storage
  • Extensible Bookmark Providers for customization
  • Flexible Query System
  • Clean Architecture for ease of code reuse and maintainability


Background

Studies from the late 1990s show that while revisitations of pages previously seen counted for roughly 39% of all page navigations (see Google Scholar), Bookmarks and History usage was low (1-3%), despite the fact that roughly 20% of those revisitations were to pages seen > 10 URLs ago (and thus outside the usefulness range of the Back button or menu).

Autocomplete in the URL bar is a useful tool but fails to address some common desires when looking up visited pages. There is a gulf between the capabilities of that tool, the capabilities of the Bookmarks and History systems today, and the desired capabilities of those systems.

Use Cases


Details

Models

Data storage is implemented via a collection of SQLite tables:

places-erd.png

A detailed database schema complete with associations between the various tables within places.sqlite: https://wiki.mozilla.org/images/d/d5/Places.sqlite.schema3.pdf

Source code:

  • Browser front-end: mozilla/browser/components/places
  • Toolkit Services: mozilla/toolkit/components/places

Views

The MDC page has the most up-to-date information on how to use views to display information from places.

Source code: mozilla/browser/components/places/content/tree|menu|toolbar.xml

Controller

The Controller connects the Views to the Model. It is responsible for telling the UI what commands are available, enabled and executing them on the back end services.

Source code: mozilla/browser/components/places/content/controller.js

Querying History

See the MDC page for details on history querying.

Other Components

Dynamic Containers

The following are some example dynamic containers:

  • Feed Container - ping and parse RSS/Atom feeds and fill containers with their posts
  • File System Container - show folders and files from the local hard disk
  • Bonjour Container - fill a container with available network resources discovered by Bonjour Zero-Configuration Networking.
  • Address Book URLs Container - fill a container with URLs mentioned in the system address book

Data Migration

Migrating data from Netscape-bookmarks-file-1, Mork, etc, to the storage format.

Observer API

Observer APIs for extensions and other components that want to listen to backend activity:


Historical Documents

This documents are kept around for historical purposes only.

Retrieved from "https://wiki.mozilla.org/index.php?title=Places:Design_Overview&oldid=126159"