SOAP vs REST: Understanding the Architectural Differences in Web Services

When designing web services and APIs, two major architectural styles dominate the landscape—SOAP (Simple Object Access Protocol) and REST (Representational State Transfer). Both are widely used, each with unique characteristics and ideal use cases. In this post, we’ll explore the architectural foundations of SOAP and REST, highlight key communication differences, and look at where each approach shines in real-world applications.

SOAP Architecture: A Protocol-Based Approach

SOAP is a protocol-driven model designed with a strong emphasis on structure and formal standards. It uses XML for message formatting and supports complex features through the WS- specifications* (e.g., WS-Security, WS-ReliableMessaging, WS-Addressing).

This structured format makes SOAP highly suitable for enterprise-level systems that require robust security, reliability, and standardized interactions between services. SOAP messages are usually transmitted via HTTP POST, although they can also be transported using other protocols like SMTP.

REST Architecture: A Resource-Oriented Style

Unlike SOAP, REST follows a resource-based architecture. Rather than using a formal protocol, REST leverages standard HTTP methods such as GET, POST, PUT, and DELETE to perform operations on resources identified by URIs.

REST is stateless, meaning each request contains all the information needed to process it. This simplicity, combined with the option to use JSON (or XML) for data interchange, makes REST a lightweight and highly scalable choice—perfect for modern web and mobile applications, as well as microservices-based systems.

Communication Model: How SOAP and REST Differ

 

SOAP Communication

SOAP relies exclusively on XML for structured messaging. These messages are encapsulated within a standard envelope and typically sent using POST requests. SOAP also supports multiple protocols, not just HTTP.

One of SOAP's standout features is its support for advanced messaging patterns and extensions:

• WS-Security for secure messaging
• WS-ReliableMessaging for guaranteed delivery
• WS-Addressing for dynamic message routing

These capabilities make SOAP a strong candidate for applications that demand robust security, transactional reliability, and enterprise compliance.

REST Communication

RESTful APIs communicate directly over HTTP, using well-known methods:

• GET for fetching resources
• POST for creating
• PUT for updating
• DELETE for removing resources

REST emphasizes the use of URIs to identify resources and typically uses JSON for data exchange. Its stateless nature contributes to better scalability and easier caching. REST is ideal for distributed environments and applications where simplicity and performance are key.

When to Use SOAP vs REST

 

Common Use Cases for SOAP

• Enterprise Application Integration: Ideal for connecting legacy systems and handling transactions.
• Service-Oriented Architecture (SOA): Frequently used in SOA-based platforms.
• Asynchronous Operations: Good for long-running processes requiring acknowledgment.
• Security-Sensitive Applications: Built-in support for encryption, authentication, and message integrity.

Common Use Cases for REST

• Web APIs: REST is the go-to choice for public and private web services.
• Mobile App Backends: Lightweight communication is perfect for mobile environments.
• CMS and Web Portals: Easily fetch and update content through RESTful endpoints.
• IoT and Smart Devices: REST APIs are ideal for managing connected devices over the internet.

Conclusion: Choosing the Right Architecture

Both SOAP and REST have their strengths and are suited to different project needs. If you're building a secure, enterprise-level application that requires formal contracts, SOAP is often the better choice. On the other hand, if you prioritize simplicity, speed, and scalability, REST is typically more suitable—especially in today’s API-driven, microservice-based ecosystems.

By understanding the architectural and communication differences between SOAP and REST, you can make informed decisions when designing or selecting web services for your application landscape.

405 - HTTP verb used to access this page is not allowed

We get the above error when we use PUT verb when we access RESTFUL web services.

For this to work, The web site had to continue to enable WebDAV, but the web application needed to turn it off in order to support PUT and DELETE in its REST API.

Below are the approaches I followed to solve my problem.

Procedure 1:

1. In the IIS Manager, select the application that needs to support PUT.  
2. In the Features View, find WebDAV Authoring Rules.  Double-click it, or select Open Feature from the context menu (right-click).
3. In the Actions pane, find and click on WebDAV Settings....
4. In the WebDAV Settings, find Request Filtering Behavior, and under that, find Allow Verb Filtering.  Set Allow Verb Filtering to False.
5. In the Actions pane, click Apply.

Procedure 2:

1. Go to IIS Manager.
2. Click on your app.
3. Go to "Handler Mappings".
4. In the feature list, double click on "WebDAV".

5. Click on "Request Restrictions".
6. In the tab "Verbs" select "All verbs" .

7. Press OK.

Hope this helps!

Understanding SOAP and REST

Which is better SOAP or REST? One of the most common discussions. Both REST and SOAP are different approaches in writing the service oriented applications. REST is an architectural style for building client-server applications. SOAP is a protocol for exchanging data between two endpoints.

It is more appropriate if you compare REST with RPC(remote procedure call). RPC is a style of building client-server applications. Compared to RPC there won’t be generated proxy for client which is less coupled to the service.

REST relies on HTTP, requests for data[Get requests] can be cached. RPC systems not having such infrastructure even when using SOAP over HTTP.

Both REST and SOAP can used to implement similar functionality but SOAP should be used when a particular feature of SOAP is needed.

Security

Is SOAP is more secured than REST? answer is no. It is easy to make REST based service secure as it is to make SOAP service.The security in REST  is in the form of HTTP-based authentication and Secure Sockets Layer(SSL).  Because of WS-* specifications SOAP supports the end-to-end message security.

Transactions

This is another feature that SOAP and WS-*  supports where REST has none.

WS-Atomic transactions supports distributed, two-phase commit transactional semantics over SOAP-based services. REST has no support for distributed transactions. To create something like transactions in REST you create a  resource called Transaction. When client wants to do some transaction and then he creates a resource that specifies all the correct resources.

Interoperability

SOAP services are less interoperable than REST Services. In terms of platforms, For REST all you need is HTTP stack. REST has widest interoperability like mobile devices,household devices, POS devices etc. The problem in SOAP and WS-* is the large number of standards to choose from.

Metadata

There is no direct way in REST to generating client from server-side-generated metadata. In SOAP with WSDL we can generate the client proxies. In REST we can achieve the same using WADL (Web Application Description Language). WSDL makes easier in generating the proxy than writing some code fro generating for REST service.

Protocol Support

Though REST is currently tied with HTTP but you still can implement the REST features on other protocols until vendors add support for this.

IS REST is for Internet-facing apps and SOAP for enterprise apps?

Answer is no. This question comes due to lack of distributed transaction support in REST vs explicit WS-atomic transactions in SOAP.

ASP.NET doesn’t have support for distributed transactions, but does that mean ASP.NET isn’t useful for enterprises?

Enterprise applications need scalability and speed. SOAP services are much harder to scale than RESTful services. Most of the scaling features can not be used with SOAP because SOAP uses POST only over HTTP.

Conclusion

“Which is better, REST or SOAP?” is “It depends”. Both REST and SOAP has advantages and disadvantages when it comes to building the services. When you need the features that are easy to implement using REST or SOAP choose it..