EME

The basic situation when you work with the EME is that you have files in two kinds of location:

• A personal work area which you specify, located in some file system

Essentially this is a formalized directory structure that usually only you have access to. This is where you work on files.

• A system storage area

This is the EME system area where every version that you save of the files you work on is permanently preserved, organized in projects. You (and other users) have indirect access to this area through the GDE and the command line. This area's generic name is EME datastore.

EME Datastore

An EME datastore is a specific instance of the EME: the term denotes the specific EME storage that you are currently connected to through the GDE. For example, an EME datastore instance called tutorial is created, used, and removed (twice) in the course of the EME tutorial in Guide to Managing Technical Metadata. During the tutorial, a project called lesson is set up in the datastore; the user work area (sandbox) associated with it also happens to be called lesson.

Obviously, many such datastore instances can reside in an environment in which the EME has been installed. But you can only be connected to one datastore at a time: this is determined by your GDE's current EME datastore settings, reached through Project > EME Datastore Settings in the GDE main menu (on the command line the connection is specified by the value of AB_AIR_ROOT, or by specifying the -root argument to individual commands). You can change this setting and use a different datastore, but you can use only one datastore at a time in the GDE.




Projects and Sandboxes

Project Files Reside in the Datastore 

In the EME datastore, graphs and files are grouped in projects. The datastore at its highest level contains a /Projects directory. Each of its immediate contents represents a separate project, or a subdirectory containing projects.

As a practical matter, a project consists of whatever files you put in it. Formally defined, a project is a collection of Ab Initio graphs and files that have some close working association with each other: taken together, they make up a single application (graph or group of graphs) or a coherent, discrete piece of an application. They share record formats and transforms and perhaps other data as well.

Sandboxes Permit Access to the Datastore 

Projects are held in the EME datastore, and you cannot directly manipulate them. To work on a project, you must set up a working area for it on your machine called a sandbox. A sandbox is just a standard directory structure that the EME knows about and that mirrors a project area in the datastore. It is the physically accessible representation of a project. You can check out files to a sandbox or check in files from it. When you check in files, the EME updates its current versions in the datastore from the sandbox.