Question: Is there any clear definition of RPC and Web Service? A quick wikipedia search shows:

> 
> RPC: Remote procedure call (RPC) is an
>  Inter-process communication technology
>  that allows a computer program to
>  cause a subroutine or procedure to
>  execute in another address space
>  (commonly on another computer on a
>  shared network) without the programmer
>  explicitly coding the details for this
>  remote interaction. 
> 
> 
> Web Service: Web services are
>  typically application programming
>  interfaces (API) or web APIs that are
>  accessed via Hypertext Transfer
>  Protocol and executed on a remote
>  system hosting the requested services.
>  Web services tend to fall into one of
>  two camps: Big Web Services[1] and
>  RESTful Web Services.
> 
> 
> 

I am not quite clear what the real difference between the two things. It seems that one thing could belong to RPC and is kind of web service at the same time.

Is Web Service a higher level representation of RPC?

Answer: 
Remote Procedure Call (RPC) and WebService, in the sake of Functionality both go parallely. But there is a subtle difference in their way of invoking. 
An Web Service can be invoked by any application, using XML format over HTTP protocol for proceedings and its interoperable in nature, whereas in case of RPC the function can be Invoked by multi applications so it follow the path of Serialization to store the object data. It supports Binary Format over TCP protocol.
In a better approach we can brief RPC workflow, like we are executing a function through proper Socket and proper format of message, but don't know the actual existence of the particular function in client server.Even the provided socket might not be in the same server in which the function resides. But every time it give a feel like the function is located in the local. In Remote Service, the Function resides in remote machine and it can be invoked by proper format and Protocol and it allows Scalability.
• Data is formatted for transfer using XML, improving or eliminating marshalling, unmarshalling, and various other translation-related requirements normally coded by a developer. 
• Data is passed using standardized protocols such as HTTP or SMTP, which have published well-defined standards. 
• The underlying exposed service is well-defined using a known accepted mechanism, WSDL. 
• Services are found using a well-defined standard, UDDI, and the more advanced ebXML. 

Specifically WSDL provides a number of key pieces of information:

• A definition of the format of the messages that are passed between two endpoints using its and elements and appropriate schema definitions. 
• The semantics of the service: how it might be called to make a synchronous request/reply, synchronous reply-only or asynchronously communicate. 
• The end point and transport of the service via the element: that is, who provides the service. 
• An encoding via the element, that is how the service is accessed.