Microsoft BizTalk Framework Adds Messaging to XML:
Proposed Framework for XML Schemas and Exchange of Data

Netting It Out

XML's flexibility allows it to be used to solve many vexing problems. But its flexibility also creates other problems when trying to define common formats for exchanging data among applications, business partners, or with customers. There needs to be agreement on how XML data is formatted, and how it is routed among applications.

Although many groups are defining XML schemas, Microsoft has stepped up and offered a solution for defining a standard way to create schemas. [Microsoft®] BizTalk™ Framework is a specification and a framework for implementing XML schemas. It also provides a set of XML tags to be used within messages sent between applications. In fact, XML message formats may be the most significant and longest lasting legacy of BizTalk Framework.

Microsoft hopes to elicit broad industry support for BizTalk Framework. Boeing, Merrill Lynch, and the American Petroleum Institute are early BizTalk Framework supporters, as are most ERP vendors.

Microsoft will support BizTalk Framework in relevant products, including its future BizTalk Server. Herein lies one of Microsoft's key motives behind BizTalk Framework. Without the BizTalk Framework, it would have been hard for Microsoft to convince customers of the value of a "Microsoft proprietary" XML application processor. By having an open specification, customers and other ISVs can support the specification while Microsoft delivers important functionality to customers.

One of XML's greatest strengths is that it is extremely flexible and easy to extend in a standard way. Unfortunately, those are also XML's greatest weaknesses. XML is raw material, able to be molded into an endless variety of shapes and put to an almost unlimited set of uses. In art and industrial design, those are useful characteristics. In information technology, those characteristics can be problematic when multiple organizations need to exchange information and systems need to interoperate in standard ways.

Using XML syntax to create vocabularies or schemas that are solely for use within a single organization is fairly straightforward. It is when a schema is being developed for data that are going to be exchanged with business partners or customers that XML's complexity creeps into the picture. XML allows us to express the same things in an almost unlimited variety of ways. This makes it harder for applications to interoperate and for organizations to exchange data easily if the structure and format of data cannot easily be discerned.

Standard messaging formats are another key requirement for achieving XML's promise of application integration and data exchange. Although message-queuing middleware such as IBM MQSeries and Microsoft Message Queue Server are well-suited to integrating applications through asynchronous exchange of XML data, there needs to be a standard, extensible message wire format for data in order for this to occur. That is one of BizTalk Framework's most important contributions.

Microsoft is betting heavily on XML. XML is Microsoft's strategic answer to portability and interoperability. The company is defining a framework, called BizTalk Framework, that it hopes will provide standardization for how XML schemas are defined in order to facilitate the exchange of information. BizTalk Framework provides a design framework for implementing XML schemas and a set of XML tags to be used in messages exchanged between applications.

BizTalk Framework calls for the use of a subset of the schema specification (XML-Data), which Microsoft proposed to W3C in 1988. XML-Data is a vocabulary that describes the elements that may be used in a document, the attributes that may appear, and what combinations of elements and attributes are valid. (Remember that XML-Data, as well as other schema proposals, go beyond DTDs in several important areas, including specification of data types (integer, float, date, etc.), support for the XML Namespace specification, and support for open content models; moreover, all are written in XML and therefore are extensible.)

Recently, the W3C convened an activity to propose a new schema specification, which may or may not follow Microsoft's 1988 proposal. When the anticipated new schema specification is completed and ratified by W3C, BizTalk Framework will recommend that where practical, schemas written to the XML-Data subset specification be republished in the W3C recommended format.

BizTalk Framework is intended to provide a universal approach to expressing business process interchanges in a consistent and extensible framework. It would enable ISVs and corporate developers to more easily map one business process to another and exchange data than is otherwise possible today.

The specification that Microsoft has posted to its http://www.biztalk.org Web site is an early draft (version 0.8) intended to elicit comment from the industry, particularly in the area of message formats. There are other areas of the specification that Microsoft and other BizTalk Framework participants are working on that will be included in the final version of the specification. These include sequencing, security, and fully defined conversational tag support. Additional privacy features will also be covered in Version 1.0 of the specification when it is completed.

The BizTalk Framework draft specification is published on the biztalk.org site. The site will also host a repository for companies and organizations to publish vertical industry and application-specific XML schema. The site will allow both public and private posting based on the desire of the publishing organization. The repository will automatically validate schema being published and maintain schema versioning. Microsoft has stated its intention to ensure that the repository will be maintained as a reliable namespace repository for application developers.

The biztalk.org site will also host discussion groups and have XML tools and utilities posted. Microsoft is encouraging developers and schema providers to write XSL maps to map related schema to one another, in order to resolve differences and to facilitate data exchange.

Microsoft has organized a steering committee for BizTalk Framework comprised of ISVs and enterprise customers. The company's goal is to have approximately a 50/50 split between customers and ISVs. Currently, Boeing, Merrill Lynch, and the American Petroleum Institute are the most visible customer participants. Most of the major ERP vendors and supply chain vendors are also on the steering committee, and the Data Interchange Standards organization, which maintains X.12 standards, is participating as well. The latter will help gain acceptance for BizTalk Framework among the EDI community.

The BizTalk Framework can be used in any application that automates business processes, especially those that cross application or organizational boundaries. By using XML as the wire format for data interchange, any application that can parse XML can take in an XML message. Common APIs, RPCs, object models, binary data representations, and other wire formats that have to be marshalled and unmarshalled become a thing of the past.

So, what does a BizTalk Framework document look like? The Illustration below shows a simple example of a generic BizTalk Framework data document. Since BizTalk Framework leaves domain-specific content to industry groups and other domain experts, most of the tags in the Illustration relate to message exchange.

<?XML version="1.0"?>

<BizTalk xmlns:="urn:schemas-biztalk.org:BizTalk/biztalk-0.8xml">

<Body xmlns:= "urn:your-namespace-goes-here">

<Route>

<From Location ID="value" LocationType="value" Process="value"
 Path="value" Handle="value">

<To Location ID="value" LocationType="value" Address="value"
 Path="value" Handle="value">

</Route>

<MessageType>

Your XML document data goes here

</MessageType>

</Body>

</BizTalk>

Routing Tags Carry Protocol Information

In general, message-passing systems define protocol information that facilitates message exchange and processing. In BizTalk Framework, this protocol information is defined in the BizTalk Framework Tags. These tags are mandatory in every BizTalk Framework document in which routing is to be used.

Routing tags allow a program to create a response to a message it receives that can then be sent back to the calling application, no matter what that application is. The recipient application or process doesn't have to know anything about the calling program. A program that receives a BizTalk Framework message can create and route a response back to the sending application by adding a value to the "To" element with the information contained in the "From" element from an earlier message. Delivery is thereby decoupled from the application. Any delivery mechanism can be used that can parse the information in the routing block of a BizTalk Framework message.

Transferring XML data from one application to another requires that the XML document be routed from a sender to a destination. Simple URLs are insufficient, because they only represent location and do not convey rich enough information to allow data to be delivered to an application. What is critical for XML's best use as a vehicle for data exchange is for routing to be application independent. This means that routing information is not hard-wired or embedded in an application, but is filled in at the point that a request is made. This is very different from other programming models, which may have to be written to call an Object Request Broker to find the target or look up the location of the other application in a registry. With BizTalk Framework, the specific location that is to receive the data can be provided at run-time, making applications location-independent and enabling applications to look up the destination of a message at run-time.

BizTalk Framework's routing tags are defined as attributes of <To> and <From> elements. They include:

• LocationID. This attribute contains abstracted information that refers to a place where the delivery service or agent that will manage BizTalk Framework message flows can be found.
  
  
• LocationType. This is a secondary qualifier used with the LocationID attribute, which is used in cases where a delivery agent supports different types of locations.
  
  
• Process. This tag describes the name of the process that needs to be either notified or invoked when a message is delivered. This could either be a business process or a software process.
  
  
• Path. The Path attribute is used to provide a place where the delivery agent can annotate a message as it passes through a route. This allows the path back to the original sender to be traced in order to send replies.
  
  
• Handle. The Handle attribute is an abstract identifier used by the receiving application. It is used to ensure that messages are delivered to the proper instance of an application. It is used when a sequence of messages are going to be exchanged, and they have a logical relationship to one another.
  
  

The BizTalk Framework specification also contains guidelines for style to make XML documents easier to read and process and to ensure future extensibility. These style guidelines currently include:

• Specifications for names and cases. For example, names are supposed to use a style called "CamelCase." Elements that are objects, classes, or table names use UpperCamelCase and properties and references use LowerCamelCase.
  
  
• Names should represent functions
  
  
• Use of meaningful names
  
  
• Avoiding the use of private encodings, using distinct elements to separate parts of data. This lets an XML parser separate out the components.
  
  
• Some of these style guidelines represent best practices and will likely be complemented in subsequent versions of the BizTalk Framework with additional recommendations.

There are several other requirements in BizTalk Framework. For example, records are to be expressed as an element containing sub-elements for each field. When a field is a foreign key, the element containing that field becomes a container for the sub-elements representing the foreign record.

BizTalk Framework also calls for objects to be represented as elements containing a nested element for each property of the object. When a property references another object, the nesting extends to include the properties of the object that has been referenced.

BizTalk Framework recommends, for simplicity, but does not require, that all simple data be expressed as elements and sub-elements, not attributes.

BizTalk Framework is designed to work with a variety of data structures, ranging from forms to relational tables.

BizTalk Framework is significant primarily because Microsoft is putting energy and resources behind it. Microsoft will be moving very aggressively into the Business-to-Business segment of the E-Commerce market space with the next versions of its E-Commerce products, and BizTalk Framework is a critical piece of that strategy. Microsoft's plans for its next generation of E-Commerce products, including the BizTalk Server, SQL Server™, and Site Server, to be delivered around the end of 1999, hinge on its ability to allow customers to exchange data with business partners.

There will no doubt be competing proposals for XML message formats, but this is an area where it is to the benefit of customers that the industry put more effort into resolving differences than creating them. Microsoft should receive credit for taking the initiative in this area.

There are many different vertical industry efforts underway to define common vocabularies. Unfortunately, each of these efforts is taking different approach to defining schema. BizTalk Framework can provide an industry-neutral way to define schemas, allowing software developers to provide tools and applications that work across industries, rather than having to adapt to each industry's schema.

Contact
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052-6399
James Utzschneider
Program Manager
Phone: (425) 936-0229
Fax: (425) 883-8101
E-Mail: [email protected]
Internet: http://www.microsoft.com

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