Hi Jason,

The OpenERP API can definitely do what you want, and the reason is very simple: the UI indeed uses that very same API to talk with the backend. So what the UI can do, you can do it programmatically too.

However the OpenERP API is designed in a completely generic way: it is structured around models (i.e. business classes backed by database tables), which by default only offer a very simple set of methods: the CRUD basics, named create(), read(), write() and unlink()) + some utilities like import_data(), export_data(), etc. Have a look at the technical documentation for the details. The technical memento may also be a good reference. So in this sense the API is not business-centric, but the advantage is that you only need to learn one set of methods to access everything in the backend. As long as you know a given model exists, you can interact with it using the basic API, introspect it, follow relationships, etc. And that's what the UI does: to create an invoice it will call the create() method of the relevant model, passing the data that has been input by the user.

Accounting being implemented by OpenERP models like anything else, it is easily accessible using the API, for example:

• You can access invoices and refunds using the API of the account.invoice model
• You can access journal entries and journal items (the double-entry bookkeeping) using the API of the account.move and account.move.line models
• You can access payment vouchers using the API of account.voucher, and bank statements via account.bank.statement), etc.

Now, in addition to the pure CRUD part, most business models will define extra bits of API:

• Business workflows are defined on the main models (invoices, sales orders, etc.), and are driven by signals sent to the workflow when users click on certains types of buttons
• Extra API and helper methods may be defined and called indirectly by CRUD methods or bound to certain buttons on the screens

Discovering and mastering those is required if you plan to do complex things on the backend without using the UI. But they're obviously specific to each model and not well documented. The best way to learn is to read the source code of the the relevant business models you're interested in. If you're not sure where to start, one helpful thing to do is to watch the API in action by looking at the RPC calls sent by the UI when you go through the relevant business flows. To do so you can either use the network debugger of your browser and watch the XHR calls, or start the OpenERP server with the --log-level=debug_rpc_answer option and read the extra log.

To answer the last part of your question, yes there are many users who are using the OpenERP API to manage their business data remotely from other applications (including invoices, accounting, and everything else). Unfortunately I do not have any code pointer to share, as most of them are doing that for specific use cases dealing with other proprietary products, or simply do not consider their use case generic enough to publish the source code. Perhaps other people could elaborate on this by providing links?

I hope that helps a bit...