Question

Fill in the blanks in each of the following statements: a) A SOAP RPC requires the name of the method being called, its parameters and __________. b) A SOAP __________ contains information that describes the content, recipient and processing requirements of a SOAP message. c) SOAP can pass through most firewalls because __________ is its transport mechanism. d) SOAP RPCs use the HTTP _________ model

Short answer

a) namespace, b) header, c) HTTP, d) request-response

Step-by-step solution

Understanding SOAP RPCs

A SOAP Remote Procedure Call (RPC) involves invoking a method on a remote server. For it to work, the request must include not only the method name and parameters but also an additional component that is crucial for the process.

Identifying the Additional Component in SOAP RPCs

SOAP RPCs require, apart from the method name and parameters, the 'namespace' to resolve method identity and potential conflicts accurately.

Describing a SOAP Header

SOAP messages are structured in a way that the header contains information essential for processing. This includes describing the content, identifying the recipients, and outlining the processing requirements or rules for the message.

Recognizing SOAP's Transport Mechanism

SOAP messages are typically transmitted over the Internet using an application protocol as a transport mechanism, which is HTTP (Hypertext Transfer Protocol). This allows SOAP to pass through many firewalls that are configured to allow HTTP traffic.

SOAP RPCs and HTTP Model

SOAP RPCs are built on the HTTP request and response model. This structure allows them to mimic typical web page interactions while invoking remote operations.

Key concepts

Remote Procedure Call (RPC)

The concept of a Remote Procedure Call, or RPC, in SOAP is central to how web services communicate over the internet. It acts like making a function call but over networks to a remote server. This process enables a software program to execute a protocol that initiates the execution of a method on a server located at a different address. This essentially means an application can request a service from a program located on another computer in a network.

• SOAP RPC requires the name of the method to be called.
• It needs the parameters that the method takes.
• A crucial additional component known as the 'namespace' is required. This helps ensure the correct method is executed, avoiding any conflicts by properly identifying each method.

This capability makes it easier for systems to communicate and perform tasks as if they were all part of the same environment.

HTTP Transport

HTTP Transport is an operational backbone of SOAP because it utilizes the HTTP protocol to transmit messages. HTTP, which stands for Hypertext Transfer Protocol, is a widely used protocol on the web known for its reliability and ability to traverse through firewalls. This characteristic is beneficial for SOAP as it permits SOAP messages to be sent and received over the internet without being hindered by most network security measures.

• HTTP ensures that SOAP messages can mimic the typical request-response cycle of the web.
• This process allows for effective communication between web services and clients.
• Its universal acceptance by network security systems aids in seamless integration and delivery of messages.

SOAP's usage of HTTP Transport makes it highly compatible with the web's existing infrastructure, facilitating widespread adoption.

SOAP Message Structure

Understanding the SOAP Message Structure is key to grasping how SOAP functions. At its core, a SOAP message is an XML-based packet of data that is transmitted over the network. The structure ensures that any additional requirements for message processing are included and observed during transmission.

A SOAP message contains:

• Envelope: The outermost element that defines what's in the message and how to process it.
• Header: This section contains optional information like authentication data and transaction specifics, which may define how intermediaries should process the message.
• Body: Includes the call and its parameters, or the response to a call.
• Fault: This is an optional part of a SOAP message that appears when there's an error during processing.

The header is especially important as it contains metadata that describes the content, identifies the recipient, and provides instructions on processing requirements.

Namespaces in SOAP

Namespaces are a pivotal feature in SOAP that help prevent name conflicts in XML documents, which is particularly helpful when different applications need to communicate. In the context of SOAP, namespaces are used to ensure that XML document elements are unique and correctly identified.

• Namespaces enable the separation of elements and attributes that might have identical names but different meanings.
• This is accomplished through using namespace URI (Uniform Resource Identifier) which distinctly categorizes elements.
• Within SOAP RPCs, namespaces are essential as they ensure the unique identification of callable methods, thus facilitating accurate method execution.

By defining distinct namespaces, SOAP makes it easier for developers to manage and integrate services without the fear of overlapping identifiers.