Canonical Model is a design pattern used to communicate between different data formats. A form of Enterprise Application Integration, it is intended to reduce costs and standardize on agreed data definitions associated with integrating business systems. A Canonical Model is any model that is canonical in nature, i.e. a model which is in the simplest form possible based on a standard, common view within a given context. Often the term Canonical Model is used interchangeably with Canonical Data Model, an enterprise design pattern which provides common data naming, definition and values within a generalized data framework.
Adoption of a comprehensive enterprise integration strategy often entails a move to a message-based integration methodology. A typical migration from point-to-point interfacing to message-based integration begins with a decision on the middleware to be used to transport messages between endpoints. Often this decision results in the adoption of an Enterprise Service Bus (ESB) or Enterprise Application Integration (EAI) solution. Most organizations also adopt a set of standards for message structure and content (message payload). The desire for consistent message payload results in the construction of an enterprise or business domain Canonical Model or adoption of an XML message standard used as the basis for message objects[1].
The goal of the Canonical Model is to provide a dictionary of reusable common objects and definitions at an enterprise or business-domain level to enhance system interoperability. "A Canonical Data Model allows developers and business users to discuss the integration solution in terms of the company's business domain, not a specific package implementation. For example, packaged applications may represent the common concept of a customer in many different internal formats, such as 'account', 'payer', and 'contact'. Defining a Canonical Data Model is often the first step to resolving cases of semantic dissonance between applications." [2] Enterprise integration models provide a foundation for a decoupled, consistent, reusable integration methodology which can be implemented using messaging supported by middleware products. Message payloads (business data content) in the form of XML schema are built from the common model objects thus providing the desired consistency and re-usability while ensuring data integrity.