Chapter 4. Architecture

In this chapter, we will explore the following concepts:

• Documentum architecture layers

• Platform components

• Communication patterns

Documentum Platform

The term Documentum means different things to different people. Some people think of the repository, some think of Webtop, and the others think of a custom content application they are exposed to.

In order to grasp the full capabilities and organization of Documentum, it is best to think of it as a set of core product components, an additional set of optional product components (some of which are frequently used), and an unbounded set of custom applications.

EMC offers over 50 product components for the Documentum platform. In order to make this complexity manageable, from the standpoint both of comprehension and of software maintenance, the platform is also organized as a framework. The framework provides guidelines, standards, and tools for using and extending the platform.

The Documentum platform is organized in layers...

Documentum Platform

The term Documentum means different things to different people. Some people think of the repository, some think of Webtop, and the others think of a custom content application they are exposed to.

In order to grasp the full capabilities and organization of Documentum, it is best to think of it as a set of core product components, an additional set of optional product components (some of which are frequently used), and an unbounded set of custom applications.

EMC offers over 50 product components for the Documentum platform. In order to make this complexity manageable, from the standpoint both of comprehension and of software maintenance, the platform is also organized as a framework. The framework provides guidelines, standards, and tools for using and extending the platform.

The Documentum platform is organized in layers, just like the well-known n-tier architecture for enterprise applications. The similarity is more in terms of the benefits of using layers and less in...

Layered Architecture

Layered architectures are a norm in enterprise applications today. Layers can separate components by various criteria such as purpose or role, technology, and dependence on other components. There are various benefits of layered architectures including:

• Complexity becomes manageable from multiple perspectives — comprehension, design, implementation, testing, and deployment.

• Encapsulated implementation of a layer makes it possible to replace the layer with another implementation.

• Multiple higher-level layers can utilize the functionality of the lower-level layers, thus promoting reuse.

In this discussion, we will use the term tiers in the popular sense — presentation (view), logic, and persistence (data/content storage). We will describe the Documentum platform architecture in terms of layers.

The Documentum platform is organized in four layers — Repository Layer, Content Services Layer, Component and Development Layer, and Application Layer. Each layer serves a specific...

Repository Layer

The Repository Layer provides storage for the platform and consists of the content repository, which uses file stores and a relational database as its components. The file store is a logical storage area and can be a file system of the host operating system (OS) or a Content-Addressed Storage (CAS), such as EMC Centera. CAS uniquely identifies a content item using a digital fingerprint (also known as ID or logical address) of the content item rather than a file system path of the content item. Other alternatives such as streaming servers and even relational databases can be used as file stores.

Optionally, the repository can also maintain a full-text index of all text-based content assets stored within the repository. For example, such content may include documents, text files, HTML files, XML content, and close-captioned video content.

In a Documentum deployment, the Content Server, the file store, and the database can all be hosted on separate physical machines...

Content Services Layer

As discussed in a previous chapter, a repository is brought to life by the Content Server. The Content Server manages the repository and provides a low-level interface for interaction with the repository. The Content Services Layer (also referred to as Services Layer) provides application-level services for organizing, controlling, sequencing, and delivering content to and from the repository.

The Content Services Layer consists of the following core services:

• Library Services: These services consist of checkin/checkout, versioning, and basic rendering. These concepts are discussed in Working with Content (Chapter 2).

• Security Services: These services consist of authentication, authorization, and auditing. These concepts are discussed in the chapter related to security.

• Workflow Services: These services automate business activities and policies for repository content. Workflows are discussed in Chapter 11.

• Lifecycle Services: These services automate the lifecycle...

Component and Development Layer

The Component and Development Layer, also known as Interface Layer, provides access to the repository content and the content services. This layer consists of predefined components and their application programming interfaces for enabling customization, integration, and application development. This layer consists of Documentum Foundation Classes (DFC), a set of standards-based APIs, Business Object Framework, WDK, Portlets, and Desktop components.

Documentum Foundation Classes

Documentum Foundation Classes (DFC) expose the Documentum object model as an object-oriented library for applications to use in the form of Java and Component Object Model (COM) libraries. DFC provides higher-level capabilities such as virtual document management, XML content-management, and business objects. Virtual documents combine component documents into a larger document. Virtual document management is described in the chapter Virtual Documents (Chapter 14).

Standards-Based...

Application Layer

The Component and Development Layer builds the bridge to the content services layer for applications that are part of the Application Layer. It is the Application Layer that makes the platform available to human users. The application layer essentially opens up the platform for any type of use that can utilize content-management capabilities. The Applications in this Layer can be categorized into web-based applications, desktop applications, portal applications, and enterprise applications.

Some such existing applications are described in the next section, while more custom applications can be created using the capabilities made available by the Component and Development Layer.

Webtop is the essential web application for interacting with a repository. Webtop is a WDK application and is built on top of the WDK components. Documentum Administrator is very similar to Webtop but provides additional administrative capabilities for managing repositories.

Digital Asset Manager...

Integration Services

Documentum offers options in all layers for integration with other systems providing the flexibility and granularity needed to meet business and technical requirements. Integration Services span the four layers and do not constitute a separate layer. The layers are as follows:

1. 1. The Application Layer has access to the full range of capabilities offered by the Component and Development Layer. There are several dedicated Documentum integrations available for popular enterprise applications such as SAP and Siebel. Custom integrations can also be developed using WDK or DFC components.

   For example, a loan management financial application can utilize the document management capabilities of the Documentum platform. A custom integration can create an interface suitable for the financial application and utilize DFC to interact with the repository. Once this integration is in place, the financial application can create, update, retrieve, and delete documents with appropriate...

Communication Patterns

Operation of the Documentum platform involves basic communication patterns, which are repeated over and over. In order to understand these patterns, it is important to first identify the components that participate in such communication.

Key Components

The following figure shows the key components involved in communication with Content Server:

We are already familiar with the Content Server it manages the repository. Any content management communication ultimately needs to reach it.

Documentum Client Library (DMCL) is a low-level API that exposes full Content Server functionality. DMCL supports Remote Procedure Call (RPC) capability, enabling clients to connect to the Content Server without dealing with network details. Even though direct access to DMCL is available, it is not recommended for clients to directly interact with DMCL. Rather DFC wraps around DMCL and exposes a higher-level API for the clients to use.

DFC is implemented in Java and it also provides a Java...

Documentum Product Notes

The interaction of Content Server with a repository deserves some attention. One Content Server serves one repository but multiple Content Server instances can also serve the same repository. This is usually done for performance reasons (load balancing) where the expected number of concurrent requests to one instance may cause it to become overloaded.

Multiple Content Server instances may also be used for high availability (failover) where failure of one Content Server instance doesn't make the repository unavailable since the other instance(s) can serve the repository.

The Content Server is supported by Method Servers, which can execute methods. In this context, a method is a piece of code that can be scheduled to run as a job or can be invoked from a workflow activity or a lifecycle action. Let's see the following Method Servers:

• Dmbasic Method Server: This executes methods written in Docbasic. Docbasic is a programming language, somewhat similar to Visual Basic...

Checkpoint

At this point you should be able to answer the following key questions:

1. 1. What are the four layers of Documentum architecture? What are their roles? What are the key components of each layer?

2. 2. What is the fundamental communication pattern for interacting with the Content Server? How is it different from interaction with a WDK application?

Test Your Understanding

1. 1. The layers of Documentum architecture map one-to-one on the tiers of application architecture (True/False).

2. 2. The following layers are part of the Documentum platform layers:

   a. Application layer

   b. Connection layer

   c. Content Services layer

   d. Repository layer

3. 3. The following product provides the ability to search for words inside document contents:

   a. Java Method Server

   b. Content Server

   c. Index Server

   d. Content Intelligence Services

4. 4. BOF is a part of DMCL (True/False).

5. 5. DFC is written in Java but it can be accessed from the .NET platform using:

   a. Java-COM Bridge

   b. Primary Interop Assembly

   c. Connection Broker

   d. DMCL

6. 6. Which of the following is true:

   a. Content Server projects to connection broker

   b. Connection broker projects to repository

   c. Repository projects to Content Server

   d. Repository projects to connection broker

7. 7. A client finds out about available connection brokers using:

   a. server.ini

   b. client.ini

   c. dmcl.ini

   d. dmconnbroker.ini

8. 8. The...