This is the plan.

I’m going to develop a browser based book-keeping and financial accounting system from scratch and document the development here.
I’ll make to work in progress and the completed system freely available.
My hope is to learn more about web/application application development, open-source and the development community online.
The working title for my app is Depecuniae (Late night, coffee, Babelfish, don’t ask).
Ok let’s go.
Book keeping
I’m not an accountant; I’m a developer with a lot of experience in financial systems in Ireland and the United Kingdom. I hope to fill in any gaps in my knowledge with the help of professionals.

In theory, financial accounting systems are quite simple. Record transaction data, process it, store it, and generate report information. It has rules and built in checking already decided over centuries. The user experience is the greatest challenge, and takes the lion’s share of the development time.
It’s important to bear this in mind. The data processing will be quite rigid and the interface will be a moving target.
Here’s a quick wanted list in two parts to get us started. It will be amended, extended, reduced and possibly replaced entirely over time.
The processing part of the system:
• must support accounting standards.
• must accept transaction input.
• must maintain balances.
• must generating reports.
• must produce periodic analysis including financial accounting reports.
• must be coherent. It must have traceability.
• must be secure.
• should be highly configurable.
• should support multiple companies, branches and locations.
• should support multiple currencies and exchange rates.

The interface part of the system:
• must be pleasing and easy to use.
• should be multi user and employ agile user control.
• should be accessible to users with special needs.
• should support multiple languages.
• should accept electronic as well as manual input.
• should generate electronic output.

Like any list it is incomplete and lacking in detail. Also, many of the list requirements overlap with others.