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XLANG is a language used for specifying message exchange patterns (MEPs) in distributed systems, particularly in the context of web services and service-oriented architecture (SOA). XLANG was developed by Microsoft as part of the BizTalk Server product, which is a business process management (BPM) and enterprise application integration (EAI) platform. The XLANG language is based on XML (eXtensible Markup Language). It provides a way to define and compose complex, long-running business processes by specifying the interactions between different services.

Overview of XLANG

The main purpose of XLANG is to provide a means for describing and orchestrating the interactions between different services within a distributed system. These interactions are typically represented as message exchanges between the services, and XLANG is used to specify the sequence and conditions under which these messages occur.

XLANG provides several key features and constructs for defining and composing business processes, including:

  • Messages: XLANG uses the concept of messages to represent the data exchanged between services. Messages are defined using XML schemas and can contain various data types, such as strings, numbers, and complex structures.
  • Ports: Ports are the communication endpoints through which services interact with each other. XLANG defines the structure of ports, including the types of messages they can send and receive, as well as the protocols and transports used for communication.
  • Orchestration: XLANG allows developers to define the logic and control flow of a business process by orchestrating the interactions between services. This is achieved using constructs such as parallelism, loops, conditional branching, and exception handling.
  • Transactions: XLANG supports long-running transactions, allowing developers to define the boundaries of a transaction, as well as the actions to be taken in case of success or failure.
  • Correlation: Correlation is used in XLANG to associate related messages within a business process, enabling the tracking and managing of message exchanges across multiple services.

Relationship to Other Technologies

XLANG has been influential in developing other technologies and standards related to web services and service-oriented architecture. In particular, XLANG was one of the inspirations for developing the Web Services Choreography Description Language (WS-CDL) and the Business Process Execution Language (BPEL).

While XLANG is specific to Microsoft BizTalk Server, BPEL has emerged as the more widely adopted standard for defining business processes in web services and SOA environments. BPEL is supported by various vendors and platforms, making it a more portable and interoperable option for organizations implementing service-oriented architectures.


XLANG is a language developed by Microsoft for specifying message exchange patterns and orchestrating business processes in distributed systems, particularly in the context of web services and service-oriented architecture. Although XLANG has been influential in developing other standards, such as BPEL, it remains primarily associated with Microsoft BizTalk Server. Organizations implementing service-oriented architectures should carefully consider the available options for specifying and orchestrating business processes, considering factors such as vendor support, interoperability, and portability when choosing between XLANG and alternative technologies like BPEL.

See Also