Service oriented architecture, SOA as it is often referred to, is today "the use of web services to integrate the data flow between systems".  The term SOA has been around much longer than web services.  When I first heard the term, it referred to a component approach to software development.  The benefit of adopting a SOA software architecture was to allow teams to work on modules with out having to be constantly concerned about the interaction between modules.  Each software module acts as a service component to the application.  The interaction between modules is defined through APIs that rarely change.
Business Process Management systems orchestrate and choreograph the flow of tasks between systems and performers.  The orchestration of task data movement between systems relies on APIs to exchange system data.  The APIs may be web service APIs or the more modern REST API.  In this form of deployment the BPM system can be an effective systems integration framework. 
The CHALEX BizFlo system with its REST APIs to the BPM workflow and DAM asset management service is a uniquely agile framework for systems integration.  The workflow model defines the routes between performers and systems acting to complete tasks for their assigned roles.  People and systems act in support of the workflow, and the workflow engine records all activities and manages all assignments to service providers, be they man or machine. 
The benefit of this approach to systems integration is the agile way in which changes can be made and new applications created.  The BizFlo framework is also a multi-tenant SaaS  platform where affiliated groups can function independently from one another on a single system.   Any number of system integrations through the BizFlo REST APIs can be created and managed as a SaaS service.  CHALEX has integrated the Cozimo file annotation service, the MarkLogic Server, and is currently adding the OpenBravo ERP system. 
The future of systems integration may well be managed through a drag and drop workflow modeling tool that quite literally automates systems integration.