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/*!

\page organizeradvanced.html

\title Qt Organizer API Advanced Usage
\section1 Introduction

This section provides some detailed information on more advanced topics
regarding the Qt Organizer API.

\section2 The Detail Model

While QOrganizerItem and its subclasses provide methods for data access and
manipulation which should be sufficient for most purposes, it is actually a
generic container that can hold arbitrary data in the form of \e details. In fact,
functions for manipulating items, such as QOrganizerItem::displayLabel() or
QOrganizerEvent::setRecurrenceRule() are merely convenience functions that
perform operations on the underlying details of an item. A QOrganizerItem
consists of nothing more than the details it contains, as well as an id and the
id of its collection.

A QOrganizerItemDetail is a single, cohesive unit of information that is stored
in an item. A detail may have specific meta-data associated with it, as well as
access constraints which may apply to the detail (e.g., read-only, irremovable,
etc).

A list of all standard details defined by this API are listed
\l{QOrganizerItemDetail Leaf Classes}{here}.

Some details are read-only (such as the modification timestamp of an item) or
irremovable (like the type of an item), but most are freely modifiable by
clients. The QOrganizerItem::details(), QOrganizerItem::detail(),
QOrganizerItem::saveDetail() and QOrganizerItem::removeDetail() functions can be
used to manipulate these details.

It is important to note that details are implicitly shared objects with
particular semantics surrounding saving, removal and modification.

\section2 Optimizing Item Retrieval

Clients can inform the manager that they do not require certain details from an
item, which can allow a manager to optimize item retrieval. In this way, the
client can inform the manager that they are not interested in any binary blob
data (e.g., images) in retrieved items. These restrictions can be specified by
providing a QOrganizerItemFetchHint as an argument to the retrieval operation.

Note that if the item already exists in the database, it will be completely
replaced. This means that clients should not save any item which was retrieved
with a non-empty fetchHint defined, or data loss may occur.

\section1 The Organizer Manager and Manager Engines
\section2 The Organizer Manager

Access to organizer items is provided by implementations of the Qt Organizer
\l{QOrganizerManager}{manager} API. Each manager may support different
capabilities (for example, the ability to store certain datatypes, the ability
to natively filter on different details or details of different definitions, the
provision of locking mechanisms, the provision of changelog information, etc)
which are reported by the manager on request. The manager therefore provides
access to detail definitions and collections of organizer items stored in
different datastores, in a platform and datastore independent manner.

The QOrganizerManager is in fact a client-facing interface through to a
platform-specific manager engine (which is implemented as a Qt plugin). While
clients never interact directly with the manager engine, they may need to be
aware of limitations of individual engines, or differences between engines. The
API offered through QOrganizerManager allows clients to retrieve this
information for the engine which provides the functionality exposed through a
particular QOrganizerManager.

\section2 Storage Considerations

A QOrganizerManagerEngine may provide an aggregated view of multiple physical
datastores, some of which may be remote datastores. Clients of the API are aware
only that the data is managed by a QOrganizerManagerEngine with a particular
URI. It is possible that multiple different engines will have overlap in the
datastores which they aggregate, and in that case the way in which those engines
were implemented will determine whether operations are thread-safe or not.

Since the data may physically be stored in a remote datastore, any operations
may be dominated by the return-trip-time of communications with the remote
datastore. As such, \b{it is recommended that clients use the asynchronous
client API to access organizer information from any QOrganizerManager.}

\section2 Provided Engines

The Qt Organizer module includes several backends already, some of which are
designed to interface with the default calendar on their particular platform.

\section3 In-Memory Example Engine

The in-memory engine identifies itself as the \c memory engine.

The in-memory engine supports the default schema, and provides almost all
functionality available through the Qt Organizer API; however, all data
is stored in-memory and is not persisted in any way.

\section1 Manager Settings and Configuration

Users of the items API can define which backend they wish to access if a manager
for that backend is available. The list of available managers can be queried
programmatically at run-time, and the capabilities of different managers can be
ascertained by inspecting a QOrganizerManager instance. Furthermore, some
managers can be constructed with parameters which affect the operation of the
backend.

\section2 Querying a Manager for Capabilities

Different managers will support different capabilities and details. Clients can
use the meta data reporting functions of QOrganizerManager to determine what the
capabilities of the manager they have instantiated might be.

\section2 Loading the Manager for a Specific Backend

The client can choose to load a manager for a specific backend. While the engine
could be found and retrieved using a more advanced plugin framework (such as the
Qt Service Framework), this code assumes that the client has prior knowledge of
the backend in question:

\code
     QOrganizerManager specificManager("memory");
\endcode

Clients may wish to use this feature of the API if they wish to store or
retrieve item information to a particular manager (for example, one that
interfaces with a particular online service).

\section2 Loading a Manager with Specific Parameters

The client can load a manager with specific parameters defined. The parameters
which are available are backend specific, and so the client has to know which
parameters are valid for a particular backend, and what argument it takes.

\section2 Meta Data API

The QOrganizerManager class provides a static function
QOrganizerManager::availableManagers() which allows clients of the API to
determine (at run time) which plugins (managers) are available for use.

Clients of the API also need to be able to determine (at run time) what the
capabilities of a given plugin (organizer item manager) are. The
QOrganizerManager class provides API to query the capabilities of a given
manager with the following synchronous functions:

\list
\li \l{QOrganizerManager::supportedFilters()}{supportedFilters()}
\li \l{QOrganizerManager::supportedItemDetails()}{supportedItemDetails()}
\li \l{QOrganizerManager::supportedItemTypes()}{supportedItemTypes()}
\endlist

A given manager is identified by its URI. The URI consists of the manager's
name, any relevant parameters which were used during instantiation of the
manager, and the version of the manager. While the name of the manager
identifies the plugin which provides the functionality, you cannot guarantee
that the data available through one manager will be available through another
with the same name (for example, if one parameter tells the plugin to store and
retrieve organizer information from a particular online service or local file).

The synchronous API offered to allow run-time querying of a manager's metadata
includes:

\list
\li \l{QOrganizerManager::managerName()}{managerName}
\li \l{QOrganizerManager::managerParameters()}{managerParameters}
\li \l{QOrganizerManager::managerUri()}{managerUri}
\li \l{QOrganizerManager::parseUri()}{parseUri}
\li \l{QOrganizerManager::buildUri()}{buildUri}
\endlist

The functionality that the above functions provide is only available through
synchronous API.

*/
