Rogerio Atem de Carvalho and Rafael Monnerat
Enterprise resource planning systems are generally known as large, proprietary, and highly expensive products. In 2001, work on an open source ERP system known as ERP5 (http://www.erp5.com) began in two French companies, Nexedi (its main developer) and Coramy (its first user). ERP5 is named after the five main concepts that compose its core. It is based on the Zope project and the Python scripting language, both of which are also open source.
We have found that ERP5 is exceptionally easy to enhance, and easy for both developers and users to build on. One reason is that we adopted an innovative document-centric approach, instead of a process- or data-centric paradigm. The core idea of a document-centric paradigm is that every business process relies on a series of documents to make it happen. The document's fields correspond to the structure of the process—that is, the fields reflect the data and the relationships among this data. Thus, if you watch how the business experts who use the ERP5 system navigate through the documents, you will discover the process workflow.
Zope's Content Management Framework ( CMF) tools and concepts supply the technology behind this approach. Each instance of the CMF, called a portal, contains objects to which it offers services such as viewing, printing, workflow, and storage. A document structure is implemented as a Python portal class, and its behavior is implemented as a portal workflow. Therefore, users interact with web documents that are in fact views of system objects controlled by proper workflows.
This chapter will show how this document-centric paradigm and a unified set of core concepts make ERP5 a highly flexible ERP. We will illustrate these ideas by explaining how we used rapid development techniques to create ERP5's project management module, Project.
ERP is software that aims to integrate all the data and processes of an organization into a unique system. Since this is a real challenge, the ERP industry offers different versions of the same ERP software for different economic segments, such as oil and gas, mechanical, pharmaceutical, automobile, and government.
ERP software generally consists of a series of modules that automate the operations of the organization. The most common modules include finance, inventory control, payroll, production planning and control, sales, and accounting. Those modules are designed for customization and adaptation at the user's site, because even though the organizations of a given economic segment share certain common practices, every organization wants to adapt the ERP system to its specific needs. ERP software also evolves quickly to accompany the evolution of the businesses it serves, and more and more modules are added to it over time.