Introduction

As mentioned in the System overview, the OME system has been designed to follow a standard client-server architecture. Image pixel data resides on one or more image servers, while image metadata resides in a relational database on a single data server. The remote framework is the protocol specification and API for communicating with an OME data server and for retrieving image metadata from it.

Note that if your application communicates with another OME system by transferring OME-XML documents, you will not use the Remote Framework. The framework is only needed for talking to an OME data server directly.

On of the main design goals of the remote framework is simplicity. It is meant to provide a means of reliably retrieving the image metadata from an OME data server with a minimum of fuss.

The Remote Framework consists of three major parts:

• A logical model in which remote function calls can be made. This model specifies the logical primitive and compound data types that remote framework methods can operate on.

• An extensible set of methods which provide the access to the underlying metadata on the data server.

• A network transfer protocol. This specifies how values in the logical type model are turned into binary strings sent across the network wire. It also specifies how function requests and results are transferred across the network, and how connections to the data server are made.

The logical model and remote methods are defined in such a way that they are completely independent of the network transfer protocol. We currently use XML-RPC as the transfer protocol, but this is not an explicit requirement of the remote framework. The existing server and client components have both been written in such a way that a different transfer protocol could be used as a drop-in replacement. Any transfer protocol is acceptable, as long as it can represent all values defined by the logical type model.