A third layer in the architecture contains the discovery of trading partner requirements needed to do businesses electronically. A business process team in ebXML defined a meta-model that describes patterns of processes used to achieve business goals. These processes contain the message sequences, called choreographies, and detail the data actually exchanged among parties. Another critical feature, and one that also separates ebXML from most other vocabularies, is core components , the reusable data items found in business messages, designed by another ebXML team. While ebXML defines these components as semantically neutral objects, their actual meaning in business messages depends on their context, provided by the business domain and industry in which they are found.
Core components can be single elements or aggregates , defined as natural collections of elements.
A telephone number, for example, can contain a country code, city or area code, and number, which when strung together constitutes an aggregate. To illustrate the use of core components, consider how different businesses and industries use different terminology to represent the same idea, and in some cases even the same person. Airlines call the person with an airplane ticket a passenger, while that same person can buy a gift at a store within minutes of landing and be called a buyer. He or she can send the gift home with a package delivery service who will call the party a shipper, from a hotel who calls the individual a guest. Thus, the same person engages in several different transactions with several different businesses, and with much the same kind of data, but is called by a different name each time.