Patterns: Implementing Self-Service in an SOA Environment

54 Patterns: Implementing Self-Service in an SOA Environment

4.1 An introduction to the node types

A Runtime pattern consists of several nodes representing specific functions.

Most Runtime patterns consist of a core set of common nodes, with the addition

of one or more nodes unique to that pattern. To understand the Runtime pattern,

you will need to review the node definitions described in the following sections.

򐂰 User node

The

user node is most frequently a personal computing device (PC)

supporting a commercial browser, for example, Netscape Navigator and

Internet Explorer. The browser is expected to support SSL and some level of

DHTML. Increasingly, designers need to also consider that this node might be

a pervasive computing device, such as a personal digital assistant (PDA).

򐂰 Domain Name System (DNS) node

The

DNS node assists in determining the physical network address

associated with the symbolic address (URL) of the requested information.

The Domain Name Server node provides the technology platform to provide

host-to-IP address mapping, allowing for the translation of names (URLs) into

IP addresses and vice versa.

򐂰 Public Key Infrastructure (PKI)

PKI is a system for verifying the authenticity of each party involved in an

Internet transaction, protecting against fraud or sabotage, and for

nonrepudiation purposes to help consumers and retailers protect themselves

against denial of transactions. Trusted third-party organizations called

certificate authorities issue digital certificates, which are attachments to

electronic messages that specify key components of the user's identity.

During an Internet transaction using signed, encrypted messages, the parties

can verify that the other’s certificate is signed by a trusted certificate authority

before proceeding with the transaction. PKI can be embedded in software

applications or offered as a service or a product. e-business leaders agree

that PKI is critical for transaction security and integrity, and the software

industry is moving to adopt open standards for their use.

򐂰 Web application server node

A

Web application server node is an application server that includes an HTTP

server (also known as a Web server) and is typically designed for access by

HTTP clients and to host both presentation and business logic.

The Web application server node is a functional extension of the informational

(publishing-based) Web server. It provides the technology platform and

contains the components to support access to both public and user-specific

information by users employing Web browser technology. For the latter, the

node provides robust services to allow users to communicate with shared

Chapter 4. Runtime patterns 55

applications and databases. In this way it acts as an interface to business

functions, such as banking, lending, and Human Resources (HR) systems.

The node can contain these data types:

– HTML text pages, images, multimedia content for the client browser

– Servlets, JavaServer™ Pages™

– Enterprise beans

– Application program libraries, such as Java applets for dynamic download

to client workstations

򐂰 Web server redirector node

In order to separate the Web server from the application server, a so-called

Web server redirector node (or redirector for short) is introduced. The Web

server redirector is used in conjunction with a Web server. The Web server

serves HTTP pages and the redirector forwards servlet and JSP™ requests

to the application servers. The advantage of using a redirector is that you can

move the application server behind the domain firewall into the secure

network, where it is more protected than within the DMZ.

򐂰 Application server node

The

application server node provides the infrastructure for application logic

and can be part of a Web application server. It is capable of running both

presentation and business logic but generally does not serve HTTP requests.

When used with a Web server redirector, the application server node can run

both presentation and business logic. In other situations, it can be used for

business logic only.

򐂰 Integration server node

The purpose of the

integration server node is to interface between any front

end access channel, such as the Web, a call center, or a client/server (

fat

client

) PC, and any needed back-end application system. This can include

applications from other companies. The integration server node performs the

following kinds of services:

– Convert protocols from the front end to match what the back-end systems

understand.

– Decompose a single message from the front end (such as a Web server)

into several back-end messages (or transactions), and then recompose

the replies.

– Navigate from the front end to any back-end system that needs to be

accessed.

– In more complex cases, control the process or unit of work for a number of

back-end interactions based on a request from the front end.