Skip to main content
summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
Diffstat (limited to 'plugins/org.eclipse.emf.cdo.doc/html/Overview.html')
-rw-r--r--plugins/org.eclipse.emf.cdo.doc/html/Overview.html348
1 files changed, 174 insertions, 174 deletions
diff --git a/plugins/org.eclipse.emf.cdo.doc/html/Overview.html b/plugins/org.eclipse.emf.cdo.doc/html/Overview.html
index 7b3efa9f6d..d53df26fbf 100644
--- a/plugins/org.eclipse.emf.cdo.doc/html/Overview.html
+++ b/plugins/org.eclipse.emf.cdo.doc/html/Overview.html
@@ -1,174 +1,174 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
-<HTML>
-
-<HEAD>
-<TITLE>Overview (CDO Model Repository Documentation)</TITLE>
-
-<LINK REL="STYLESHEET" HREF="book.css" CHARSET="ISO-8859-1" TYPE="text/css">
-
-<SCRIPT type="text/javascript">
-function windowTitle()
-{
- if (location.href.indexOf('is-external=true') == -1) {
- parent.document.title="Overview (CDO Model Repository Documentation)";
- }
-}
-</SCRIPT>
-<NOSCRIPT></NOSCRIPT>
-</HEAD>
-
-<BODY BGCOLOR="white" onload="windowTitle();">
-<!-- <div class="help_breadcrumbs"><a href="" title="CDO Model Repository Documentation">CDO Model Repository Documentation</a></div> -->
-
-<table border="0">
- <tr>
- <td width="100%"><h1>Overview</h1></td>
- <td align="right" valign="middle" nowrap>&nbsp;<a href="programmers/index.html" title="Forward to Programmer's Guide"><img src="../images/forward.png" border="0"></a></td>
- </tr>
-</table>
-<p class="author">Author: Eike Stepper</p>
-<p>
- CDO is a pure Java <i>model repository</i> for your EMF models and meta models. CDO can also serve as a
- <i>persistence and distribution framework</i> for your EMF based application systems. For the sake of this overview a
- model can be regarded as a graph of application or business objects and a meta model as a set of classifiers that
- describe the structure of and the possible relations between these objects.
- <p>
- CDO supports plentyfold deployments such as embedded repositories, offline clones or replicated clusters. The
- following diagram illustrates the most common scenario: <p align="center"><img src="cdo-overview.png"></p>
-
-
-<h2><a name="Functionality"></a>1&nbsp;&nbsp;Functionality</h2>
-<p>
- The main functionality of CDO can be summarized as follows:
- <dl>
- <dt><b>Persistence</b>
- <dd>Persistence of your models in all kinds of database backends like major relational databases or NoSQL
- databases. CDO keeps your application code free of vendor specific data access code and eases transitions between
- the supported backend types.
- <p>
- <dt><b>Multi User Access</b>
- <dd>Multi user access to your models is supported through the notion of repository sessions. The physical transport
- of sessions is pluggable and repositories can be configured to require secure authentication of users. Various
- authorization policies can be established programmatically.
- <p>
- <dt><b>Transactional Access</b>
- <dd>Transactional access to your models with ACID properties is provided by optimistic and/or pessimistic locking
- on a per object granule. Transactions support multiple savepoints that changes can be rolled back to. Pessimistic
- locks can be acquired separately for read access, write access and the option to reserve write access in the
- future. All kinds of locks can optionally be turned into long lasting locks that survive repository restarts.
- Transactional modification of models in multiple repositories is provided through the notion of XA transactions
- with a two phase commit protocol.
- <p>
- <dt><b>Transparent Temporality</b>
- <dd>Transparent temporality is available through audit views, a special kind of read only transactions that provide
- you with a consistent model object graph exactly in the state it has been at a point in the past. Depending on the
- chosen backend type the storage of the audit data can lead to considerable increase of database sizes in time.
- Therefore it can be configured per repository.
- <p>
- <dt><b>Parallel Evolution</b>
- <dd>Parallel evolution of the object graph stored in a repository through the concept of branches similar to source
- code management systems like Subversion or Git. Comparisons or merges between any two branch points are supported
- through sophisticated APIs, as well as the reconstruction of committed change sets or old states of single objects.
- <p>
- <dt><b>Scalability</b>
- <dd>Scalability, the ability to store and access models of arbitrary size, is transparently achieved by loading
- single objects on demand and caching them <i>softly</i> in your application. That implies that objects that are no
- longer referenced by the application are automatically garbage collected when memory runs low. Lazy loading is
- accompanied by various prefetching strategies, including the monitoring of the object graph's <i>usage</i> and the
- calculation of fetch rules that are optimal for the current usage patterns. The scalability of EMF applications can
- be further increased by leveraging CDO constructs such as remote cross referencing or optimized content adapters.
- <p>
- <dt><b>Thread Safety</b>
- <dd>Thread safety ensures that multiple threads of your application can access and modify the object graph without
- worrying about the synchronization details. This is possible and cheap because multiple transactions can be opened
- from within a single session and they all share the same object data until one of them modifies the graph. Possible
- commit conflicts can be handled in the same way as if they were conflicts between different sessions.
- <p>
- <dt><b>Collaboration</b>
- <dd>Collaboration on models with CDO is a snap because an application can opt in to be notified about remote
- changes to the object graph. By default your local object graph transparently changes when it has changed remotely.
- With configurable change subscription policies you can fine tune the characteristics of your <i>distributed shared
- model</i> so that all users enjoy the impression to collaborate on a single instance of an object graph. The level
- of collaboration can be further increased by plugging custom collaboration handlers into the asynchronous CDO
- protocol.
- <p>
- <dt><b>Data Integrity</b>
- <dd>Data integrity can be ensured by enabling optional commit checks in the repository server such as referential
- integrity checks and containment cycle checks, as well as custom checks implemented by write access handlers.
- <p>
- <dt><b>Fault Tolerance</b>
- <dd>Fault tolerance on multiple levels, namely the setup of fail-over clusters of replicating repositories under
- the control of a fail-over monitor, as well as the usage of a number of special session types such as fail-over or
- reconnecting sessions that allow applications to hold on their copy of the object graph even though the physical
- repository connection has broken down or changed to a different fail-over participant.
- <p>
- <dt><b>Offline Work</b>
- <dd>Offline work with your models is supported by two different mechanisms:
- <ul>
- <li>One way is to create a <b>clone</b> of a complete remote repository, including all history of all branches.
- Such a clone is continuously synchronized with its remote master and can either act as an embedded repository to
- make a single application tolerant against network outage or it can be set up to serve multiple clients, e.g., to
- compensate low latency master connections and speed up read access to the object graph.
- <p>
- <li>An entirely different and somewhat lighter approach to offline work is to check out a single version of the
- object graph from a particular branch point of the repository into a local CDO <b>workspace</b>. Such a workspace
- behaves similar to a local repository without branching or history capture, in particular it supports multiple
- concurrent transactions on the local checkout. In addition it supports most remote functionality that is known from
- source code management systems such as update, merge, compare, revert and check in.
- </ul>
- </dl>
-
-<h2><a name="Architecture"></a>2&nbsp;&nbsp;Architecture</h2>
-<p>
- The architecture of CDO comprises applications and repositories. Despite a number of embedding options applications
- are usually deployed to client nodes and repositories to server nodes. They communicate through an application
- level CDO protocol which can be driven through various kinds of physical transports, including fast intra JVM
- connections.
- <p>
- CDO has been designed to take full advantage of the OSGi platform, if available at runtime, but can perfectly be
- operated in standalone deployments or in various kinds of containers such as JEE web or application servers.
- <p>
- The following chapters give an overview about the architecures of applications and repositories, respectively.
-
-<h3><a name="Client"></a>2.1&nbsp;&nbsp;Client Architecture</h3>
-<p>
- <p>
- The architecture of a CDO application is characterized by its mandatory dependency on EMF, the Eclipse Modeling
- Framework. Most of the time an application interacts with the object graph of the model through standard EMF APIs
- because CDO model graph objects are <a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/ecore/EObject.html" title="Interface in org.eclipse.emf.ecore"><code>EObjects</code></a>. While CDO's basic functionality integrates nicely and
- transparently with EMF's extension mechansims some of the more advanced functions may require to add direct
- dependendcies on CDO to your application code.
- <p>
- The following diagram illustrates the major building blocks of a CDO application: <p align="center"><img src="programmers/client/application-architecture.png"></p>
-<p><b>See Also:</b></p>
-<ul>
- <li><a href="programmers/client/Architecture.html" title="Article in CDO Model Repository Documentation">Understanding the Architecture of a Client Application</a></li>
-</ul>
-
-
-<h3><a name="Repository"></a>2.2&nbsp;&nbsp;Repository Architecture</h3>
-<p>
- <p>
- The main building block of a CDO repository is split into two layers, the generic repository layer that client
- applications interact with and the database integration layer that providers can hook into to integrate their data
- storage solutions with CDO. A number of such integrations already ship with CDO, making it possible to connect a
- repository to all sorts of JDBC databases, Hibernate, Objectivity/DB, MongoDB or DB4O.
- <p>
- While technically a CDO repository depends on EMF this dependency is not of equal importance as it is in a CDO
- application. In particular the generated application models are not required to be deployed to the server because a
- CDO repository accesses models reflectively and the model objects are not implemented as <a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/ecore/EObject.html" title="Interface in org.eclipse.emf.ecore"><code>EObjects</code></a> on
- the server.
- <p>
- The following diagram illustrates the major building blocks of a CDO repository: <p align="center"><img src="programmers/server/repository-architecture.png"></p>
-<p><b>See Also:</b></p>
-<ul>
- <li><a href="programmers/server/Architecture.html" title="Article in CDO Model Repository Documentation">Understanding the Architecture of a Repository</a></li>
-</ul>
-
-
-<p align="right">
-&nbsp;<a href="programmers/index.html" title="Forward to Programmer's Guide"><img src="../images/forward.png" border="0"></a></p>
-<HR>
-<i>Copyright (c) 2004 - 2011 Eike Stepper (Berlin, Germany) and others.</i>
-</BODY>
-</HTML>
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
+<HTML>
+
+<HEAD>
+<TITLE>Overview (CDO Model Repository Documentation)</TITLE>
+
+<LINK REL="STYLESHEET" HREF="book.css" CHARSET="ISO-8859-1" TYPE="text/css">
+
+<SCRIPT type="text/javascript">
+function windowTitle()
+{
+ if (location.href.indexOf('is-external=true') == -1) {
+ parent.document.title="Overview (CDO Model Repository Documentation)";
+ }
+}
+</SCRIPT>
+<NOSCRIPT></NOSCRIPT>
+</HEAD>
+
+<BODY BGCOLOR="white" onload="windowTitle();">
+<!-- <div class="help_breadcrumbs"><a href="" title="CDO Model Repository Documentation">CDO Model Repository Documentation</a></div> -->
+
+<table border="0">
+ <tr>
+ <td width="100%"><h1>Overview</h1></td>
+ <td align="right" valign="middle" nowrap>&nbsp;<a href="programmers/index.html" title="Forward to Programmer's Guide"><img src="../images/forward.png" border="0"></a></td>
+ </tr>
+</table>
+<p class="author">Author: Eike Stepper</p>
+<p>
+ CDO is a pure Java <i>model repository</i> for your EMF models and meta models. CDO can also serve as a
+ <i>persistence and distribution framework</i> for your EMF based application systems. For the sake of this overview a
+ model can be regarded as a graph of application or business objects and a meta model as a set of classifiers that
+ describe the structure of and the possible relations between these objects.
+ <p>
+ CDO supports plentyfold deployments such as embedded repositories, offline clones or replicated clusters. The
+ following diagram illustrates the most common scenario: <p align="center"><img src="cdo-overview.png"></p>
+
+
+<h2><a name="Functionality"></a>1&nbsp;&nbsp;Functionality</h2>
+<p>
+ The main functionality of CDO can be summarized as follows:
+ <dl>
+ <dt><b>Persistence</b>
+ <dd>Persistence of your models in all kinds of database backends like major relational databases or NoSQL
+ databases. CDO keeps your application code free of vendor specific data access code and eases transitions between
+ the supported backend types.
+ <p>
+ <dt><b>Multi User Access</b>
+ <dd>Multi user access to your models is supported through the notion of repository sessions. The physical transport
+ of sessions is pluggable and repositories can be configured to require secure authentication of users. Various
+ authorization policies can be established programmatically.
+ <p>
+ <dt><b>Transactional Access</b>
+ <dd>Transactional access to your models with ACID properties is provided by optimistic and/or pessimistic locking
+ on a per object granule. Transactions support multiple savepoints that changes can be rolled back to. Pessimistic
+ locks can be acquired separately for read access, write access and the option to reserve write access in the
+ future. All kinds of locks can optionally be turned into long lasting locks that survive repository restarts.
+ Transactional modification of models in multiple repositories is provided through the notion of XA transactions
+ with a two phase commit protocol.
+ <p>
+ <dt><b>Transparent Temporality</b>
+ <dd>Transparent temporality is available through audit views, a special kind of read only transactions that provide
+ you with a consistent model object graph exactly in the state it has been at a point in the past. Depending on the
+ chosen backend type the storage of the audit data can lead to considerable increase of database sizes in time.
+ Therefore it can be configured per repository.
+ <p>
+ <dt><b>Parallel Evolution</b>
+ <dd>Parallel evolution of the object graph stored in a repository through the concept of branches similar to source
+ code management systems like Subversion or Git. Comparisons or merges between any two branch points are supported
+ through sophisticated APIs, as well as the reconstruction of committed change sets or old states of single objects.
+ <p>
+ <dt><b>Scalability</b>
+ <dd>Scalability, the ability to store and access models of arbitrary size, is transparently achieved by loading
+ single objects on demand and caching them <i>softly</i> in your application. That implies that objects that are no
+ longer referenced by the application are automatically garbage collected when memory runs low. Lazy loading is
+ accompanied by various prefetching strategies, including the monitoring of the object graph's <i>usage</i> and the
+ calculation of fetch rules that are optimal for the current usage patterns. The scalability of EMF applications can
+ be further increased by leveraging CDO constructs such as remote cross referencing or optimized content adapters.
+ <p>
+ <dt><b>Thread Safety</b>
+ <dd>Thread safety ensures that multiple threads of your application can access and modify the object graph without
+ worrying about the synchronization details. This is possible and cheap because multiple transactions can be opened
+ from within a single session and they all share the same object data until one of them modifies the graph. Possible
+ commit conflicts can be handled in the same way as if they were conflicts between different sessions.
+ <p>
+ <dt><b>Collaboration</b>
+ <dd>Collaboration on models with CDO is a snap because an application can opt in to be notified about remote
+ changes to the object graph. By default your local object graph transparently changes when it has changed remotely.
+ With configurable change subscription policies you can fine tune the characteristics of your <i>distributed shared
+ model</i> so that all users enjoy the impression to collaborate on a single instance of an object graph. The level
+ of collaboration can be further increased by plugging custom collaboration handlers into the asynchronous CDO
+ protocol.
+ <p>
+ <dt><b>Data Integrity</b>
+ <dd>Data integrity can be ensured by enabling optional commit checks in the repository server such as referential
+ integrity checks and containment cycle checks, as well as custom checks implemented by write access handlers.
+ <p>
+ <dt><b>Fault Tolerance</b>
+ <dd>Fault tolerance on multiple levels, namely the setup of fail-over clusters of replicating repositories under
+ the control of a fail-over monitor, as well as the usage of a number of special session types such as fail-over or
+ reconnecting sessions that allow applications to hold on their copy of the object graph even though the physical
+ repository connection has broken down or changed to a different fail-over participant.
+ <p>
+ <dt><b>Offline Work</b>
+ <dd>Offline work with your models is supported by two different mechanisms:
+ <ul>
+ <li>One way is to create a <b>clone</b> of a complete remote repository, including all history of all branches.
+ Such a clone is continuously synchronized with its remote master and can either act as an embedded repository to
+ make a single application tolerant against network outage or it can be set up to serve multiple clients, e.g., to
+ compensate low latency master connections and speed up read access to the object graph.
+ <p>
+ <li>An entirely different and somewhat lighter approach to offline work is to check out a single version of the
+ object graph from a particular branch point of the repository into a local CDO <b>workspace</b>. Such a workspace
+ behaves similar to a local repository without branching or history capture, in particular it supports multiple
+ concurrent transactions on the local checkout. In addition it supports most remote functionality that is known from
+ source code management systems such as update, merge, compare, revert and check in.
+ </ul>
+ </dl>
+
+<h2><a name="Architecture"></a>2&nbsp;&nbsp;Architecture</h2>
+<p>
+ The architecture of CDO comprises applications and repositories. Despite a number of embedding options applications
+ are usually deployed to client nodes and repositories to server nodes. They communicate through an application
+ level CDO protocol which can be driven through various kinds of physical transports, including fast intra JVM
+ connections.
+ <p>
+ CDO has been designed to take full advantage of the OSGi platform, if available at runtime, but can perfectly be
+ operated in standalone deployments or in various kinds of containers such as JEE web or application servers.
+ <p>
+ The following chapters give an overview about the architecures of applications and repositories, respectively.
+
+<h3><a name="Client"></a>2.1&nbsp;&nbsp;Client Architecture</h3>
+<p>
+ <p>
+ The architecture of a CDO application is characterized by its mandatory dependency on EMF, the Eclipse Modeling
+ Framework. Most of the time an application interacts with the object graph of the model through standard EMF APIs
+ because CDO model graph objects are <a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/ecore/EObject.html" title="Interface in org.eclipse.emf.ecore"><code>EObjects</code></a>. While CDO's basic functionality integrates nicely and
+ transparently with EMF's extension mechansims some of the more advanced functions may require to add direct
+ dependendcies on CDO to your application code.
+ <p>
+ The following diagram illustrates the major building blocks of a CDO application: <p align="center"><img src="programmers/client/application-architecture.png"></p>
+<p><b>See Also:</b></p>
+<ul>
+ <li><a href="programmers/client/Architecture.html" title="Article in CDO Model Repository Documentation">Understanding the Architecture of a Client Application</a></li>
+</ul>
+
+
+<h3><a name="Repository"></a>2.2&nbsp;&nbsp;Repository Architecture</h3>
+<p>
+ <p>
+ The main building block of a CDO repository is split into two layers, the generic repository layer that client
+ applications interact with and the database integration layer that providers can hook into to integrate their data
+ storage solutions with CDO. A number of such integrations already ship with CDO, making it possible to connect a
+ repository to all sorts of JDBC databases, Hibernate, Objectivity/DB, MongoDB or DB4O.
+ <p>
+ While technically a CDO repository depends on EMF this dependency is not of equal importance as it is in a CDO
+ application. In particular the generated application models are not required to be deployed to the server because a
+ CDO repository accesses models reflectively and the model objects are not implemented as <a href="http://download.eclipse.org/modeling/emf/emf/javadoc/2.7.0/org/eclipse/emf/ecore/EObject.html" title="Interface in org.eclipse.emf.ecore"><code>EObjects</code></a> on
+ the server.
+ <p>
+ The following diagram illustrates the major building blocks of a CDO repository: <p align="center"><img src="programmers/server/repository-architecture.png"></p>
+<p><b>See Also:</b></p>
+<ul>
+ <li><a href="programmers/server/Architecture.html" title="Article in CDO Model Repository Documentation">Understanding the Architecture of a Repository</a></li>
+</ul>
+
+
+<p align="right">
+&nbsp;<a href="programmers/index.html" title="Forward to Programmer's Guide"><img src="../images/forward.png" border="0"></a></p>
+<HR>
+<i>Copyright (c) 2004 - 2012 Eike Stepper (Berlin, Germany) and others.</i>
+</BODY>
+</HTML>

Back to the top