4. BizTalk Concepts

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4.1 Terminology

This document uses a set of BizTalk-specific terms, as defined below:

• BizTalk Framework Compliant (BFC) Server A BFC Server is represented by the set of services providing the message-processing functionality defined in the BizTalk Framework specifications.
• Application An Application is the line-of-business system where the business data or logic are stored and executed. An application also includes any additional adapters that may be required to emit or consume Business Documents (see below) and communicate with a BFC server.
• Business Document A Business Document is a well-formed XML document containing business-transaction data. This transaction data may represent a purchase order, invoice, sales forecast, or any other business information. One or more Business Documents form the body of a BizTalk Document (see below).

The BizTalk Framework does not prescribe the content or structure (schema) of individual Business Documents. The details of the Business Document content and structure, or Schema, are defined and agreed upon by the solution implementers.

• Schema A Schema is the metadata used to describe the content and structure of a class of XML documents, in particular for a class of Business Documents. This formal description is used by application developers to create systems that process corresponding Business Documents, or by parsers that validate a Business Document's conformance to the Schema at run time.

Organizations may publish their Schemas in the BizTalk Schemas Library, or through other means.

NOTE

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Schemas for Business Documents do not contain any BizTags, as described in this specification. A schema contains only those tags required to support the business transaction, as agreed to by the cooperating business entities. General requirements and guidelines for Schema implementations are defined in the BizTalk Schema Guidelines.

• BizTalk Document A BizTalk Document is a SOAP 1.1 message in which the body of the message contains the Business Documents, and the header contains BizTalk-specific header entries for enhanced message-handling semantics.
• BizTag BizTags are the set of XML tags (both mandatory and optional) that are used to specify Business Document handling. More precisely, BizTags are elements and attributes defined in this specification and used to construct BizTalk-specific SOAP header entries in the BizTalk Document. They are processed by the BFC Server, or by other applications facilitating the document interchange.
• BizTalk Message A BizTalk Message is the unit of wire-level interchange between BFC Servers. BizTalk Messages are used to send BizTalk Documents, and any related files, between BFC Servers. A BizTalk Message must always contain a primary BizTalk Document that defines the semantics of the Message within the BizTalk Framework. It may in addition contain one or more attachments (see below), including well-formed XML documents, some of which may themselves be BizTalk Documents. BizTalk Documents carried as attachments are treated just like any other XML documents and have no special significance for the semantics of the BizTalk Message. The structure of a BizTalk Message is dependent on the transport being used to carry the message and often includes transport-specific headers.
• Transport The actual interchange of BizTalk Messages between BFC servers presupposes a communication mechanism that is used to carry Messages physically from the source to the destination business entity. We use the term transport to refer to this mechanism. Transports used in this context will vary widely in their characteristics, ranging from simple datagram and file transfer protocols to transfer protocols such as HTTP and SMTP, and sophisticated, message-oriented middleware. This specification does not differentiate between transports based on their capabilities. Transport characteristics affect only the transport bindings specified in section 10.
• Attachment Attachments are generally non-XML files or other related information that is not transmitted as a Business Document within the body of the BizTalk Document. These may be related images, large compressed files, or any other information format or content that is not an appropriate Business Document.

4.2 Logical Layering

The logical application model for the BizTalk Framework is implemented in layers. The layering described here is for illustrative and explanatory purposes. As the BizTalk Framework specification definitively specifies only the wire format for BizTalk Messages and the protocol for reliable messaging, alternative logical layering may be used, provided it supports equivalent functionality, without affecting compliance with this specification. These logical layers include the application (and appropriate adapters), the BFC Server, and transport. The application communicates with other applications by sending Business Documents back and forth through BFC Servers. Multiple BFC Servers communicate with one another over a variety of transport protocols, such as HTTP, SMTP, and Microsoft Message Queue (MSMQ). The BizTalk Framework does not prescribe what these transport protocols are, and is independent of the implementation details of each.

The application is responsible for generating the Business Documents and any attachments to be transmitted to its peer(s) and submitting them to the BFC Server. The responsibility for wrapping the Business Documents in a BizTalk Document may rest with either the application or the BFC server, depending on the implementation of the BFC server. The server processes the document and any attachments and constructs a BizTalk Message as appropriate for the transport protocol. The BFC Server uses information contained in the BizTags to determine the correct transport-specific destination address. The server then hands the message to the transport layer for transmission to the destination BFC Server. The interfaces between the business application, the BFC Server, and the transport layer are implementation specific.