SOAP Data Model

This chapter describes what is SOAP data model.

SOAP Data Model is an extension of the SOAP framework specification that defines how data structures and values should be represented as a graph of nodes. SOAP Data Model is defined as an adjunct in SOAP 1.2 specification.

SOAP data model can be represented as a graph of nodes with the following 4 simple basic rules:

1. A data element with a simple value (a primitive data type value) is represented by a node with its value as the node label.

2. A data element with a compound value (an array or a structure of sub data elements) is represented by a node with directed edges pointing to nodes that represent it sub data elements. A directed edge originated from a node is called an outbound edge with respect to this node.

3. A reference to a data element is represented by a directed edge pointing to that data element. If a reference is named, the edged will be labeled with the reference name. Otherwise, a position number will be assigned to this edge, so the reference represented by this edge can be referred by this position number.

4. A data element with a compound value can only have either all outbound edges labeled, representing a data structure; or all outbound edges not labeled, representing a data array.

5. A reference to a data element is represented by a directed edge pointing to that data element. A directed edge pointing to a node is called an inbound edge with respect to this node.

Example 1 - Simple value with no reference: The following graph represents a simple value of 3.14:

   (3.14)

Example 2 - Simple value with a named reference: The following graph represents a simple value of 3.14 with a reference name of "pi":

   --- pi -->(3.14) 

Example 3 - Compound value with named sub data elements, a data structure: The following graph represents a compound value with a reference name of "currentCustomer". This compound value has 3 simple-value sub data elements referenced as "id", "name" and "isSmoking" respectively. In many programming language, this compound value is called a structure:

                         (2321)
                           ^
                           |
                          id
                           |
   --- currentCustomer -->( )-- name -->(Herong)
                           |
                       isSmoking
                           |
                           v
                        (false)

Example 4 - Compound value with positioned sub data elements, a data array: The following graph represents a compound value with a reference name of "colors". This compound value has 3 simple-value sub data elements referenced with no names, but with positions. In many programming languages, this compound value is called an array:

                (Red)
                  ^
                  |
                  0
                  |
   --- colors -->( )----1--->(Green)
                  |
                  2
                  |
                  v
                (Blue)

Example 5 - Multi references: The following graph represents two compound values sharing the same sub value.

   --- Bill -->( )--- mother --->               
                                ( )<-- Mary ---
   --- Mike -->( )--- sister --->               

Example 6 - Circular References: The following graph represents two compound values has each other as their sub values.

                 <--- son ------
   --- Bill -->( )             ( )<-- Mary ---
                 --- mother --->               

Conclusions: In my opinion, the SOAP data model is just a visual presentation of the object data model used in many object oriented programming languages. The only difference is that a data object in a programming language may also have methods.

The SOAP data model is really for another extension of the SOAP framework specification called SOAP encoding, which defines a set of rule to encoding data values into an XML format. See the next section for details.

Last update: 2007.

Table of Contents

 About This Book

 Introduction to Web Service

 Introduction to SOAP (Simple Object Access Protocol)

 SOAP Message Structure

 SOAP Message Transmission and Processing

SOAP Data Model

 SOAP Encoding

 SOAP RPC Presentation

 SOAP Properties Model

 SOAP Message Exchange Patterns

 SOAP HTTP Binding

 SOAP Perl Implementations

 SOAP PHP Implementations

 SOAP Java Implementations

 Perl SOAP::Lite - SOAP Server-Client Communication Module

 Perl Socket Test Program for HTTP and SOAP

 Perl SOAP::Lite for GetSpeech SOAP 1.1 Web Service

 Perl SOAP::Lite 0.710 for SOAP 1.2 Web Services

 Perl SOAP::Lite 0.710 for WSDL

 PHP SOAP Extension Client Programs

 PHP SOAP Extension Server Programs

 Java Socket and HttpURLConnection for SOAP

 SAAJ - SOAP with Attachments API for Java

 SoapUI - SOAP Web Service Testing Tool

 WS-Security - SOAP Message Security Extension

 WS-Security X.509 Certificate Token

 Web Services and SOAP Terminology

 References

 PDF Printing Version