The ES Repository is used in various SAP NetWeaver IT scenarios:
- Enabling Enterprise Services
- Enabling Application-to-Application Processes
- Enabling Business-to-Business Processes
ESR is the governance of SOA .This governance will provide new services as well as old one across the organization. Hence the reusability will be increase. You can make your own governance with the help of ES Repository i.e. scenario, interfaces, global data type, interface mapping and BPEL. . In other hand the registry is having the end to end information about the services i.e. technical details.
You have to create model driven development. For creating the modeling environment you have ESB (Enterprises Service Builder).For better running of any governance you need to have some model in order to support your governance directly. Here you will have models (i.e. PCM -Process component model, ISM-Integration scenario Model) to describe the operation and services used by process and others like BPEL, global data types and other. ESB will offer all models related to the ES Repository objects or you can say it will offer the modeling environment for SOA governance.
For better understanding you can take the library example where you can have all different different books in ES Repository but the services related to the books i.e. history when purchased , when issued , to whom and all other services will be hold in ES Registry. For any new book you have to maintain services, you can use old ones if you have else you can create new ones, as well. For modeling/managing/developing all these as in software visibility you can have ESB in ESR.
Like I need service for check any particular book status then first I have to search for the particular book then I have to select the book and then I will check the status of book.