perfectxml.com is pleased to bring this new section to you! In this section, we'll publish technical reports and analysis memos on latest
and future technologies based on XML. We thank The Stencil Group for supporting
us and willing to publish their reports on perfectxml.com.
About The Stencil Group:
The Stencil Group is an innovative business consulting and advisory services firm.
We work with software companies and their customers to achieve market leadership and strategic success. By focusing on pragmatic business rationale for technology solutions, we help our clients go to market more effectively, quickly, and with less risk. Our service offerings include:
The Stencil Group is based in San Francisco and was founded in 1999.
- Customer Needs Analysis
- Market Entry and Competitive Strategy
- Partnership Strategy and Channel Development Programs
- Product Roadmap and Positioning Evaluation
To learn more about The Stencil Group, visit www.stencilgroup.com .
Defining Web Services
Copyright © 2001 The Stencil Group
The label "web services" is incredibly generic. Like
any promising and loosely defined technology trend, the concepts
it describes will be subject to a great deal of speculation and
bandwagoneering in the months to come. With the aim of providing
a reference benchmarkand of separating posturing from
realitywe provide a technology and business definition. By
Brent Sleeper and Bill Robins.
The technology marketing industry has mastered the hype
lifecycle, but rarely have we seen a concept emerge from
obscurity to new new thing as quickly as "web services." While
we fundamentally believe that the concept, promise, and
implementation of web services are sound, these virtues run the
risk of getting lost in a rush of marketing showmanship.
Part of the problem is that the web services label is incredibly
generic; while perhaps more accessible than techno-jargon like
UDDI, WSDL, and all the other acronyms that collectively define
the concept, such a generic term easily can be misapplied in
ways that dilute its meaning. Indeed, we frankly expect that
many companies will co-opt the web services label in ways that
benefit their short-term positioning, but which ultimately sow
confusion in the marketplace.
To counter that confusion and to provide an introduction to
basic web services concepts, this memo documents three facets of
The Stencil Group's definition of this technology:
Author's note: The Stencil Group's recent article, "How Web Services Will Beat
the 'New New Thing' Rap," explores the issues of web
services hype and reality.
What Are Web Services?
The label "web services," as broadly applied, has two levels of meaningone specific and one conceptual:
- Specifically, web services are a stack of emerging
standards that describe a service-oriented, component-based
- Conceptually, web services represent a model in which
discrete tasks within e-business processes are distributed
widely throughout a value net.
With these meanings in mind, The Stencil Group defines web
Loosely coupled, reusable software components that
semantically encapsulate discrete functionality and are
distributed and programmatically accessible over standard
Let's examine this definition and deconstruct its meaning.
- First, web services are reusable software components.
Web services continue the long ascension of object-oriented
design in software development. Rather than requiring
programmers to write one start-to-finish set of instructions
after another, the component-based model allows developers
to reuse the building blocks of code created by others to
assemble and extend them in new ways.
- Second, these software components are loosely coupled.
Traditional application design depends upon a tight
interconnection of all subsidiary elements. The complexity
of these connections requires that developers thoroughly
understand and have control over both ends of the
connection; moreover, once established, it is exceedingly
difficult to extract one element and replace it with
another. Loosely coupled systems, on the other hand, require
a much simpler level of coordination and allow for more
- Third, web services semantically encapsulate discrete
functionality. A web service is a self-contained "applet"
that performs a single task. The component describes its own
inputs and outputs in a way that other software can
determine what it does, how to invoke its functionality, and
what result to expect in return.
- Fourth, web services can be accessed programmatically.
Unlike web sites and desktop applications, web services are
not designed for direct human interaction, and they do not
have a graphical user interface. Rather, web services
operate at the code level; they are called by and exchange
data with other software. Web services certainly will be
incorporated into software designed for human interaction,
- Finally, web services are distributed over the Internet.
Web services make use of existing, ubiquitous transport
protocols like HTTP. By piggybacking on the same,
well-understood transport as web content, web services
leverage existing infrastructure and can comply with current
corporate firewall policies.
The Web Services Technology Stack
By intent, web services are not implemented in a monolithic way,
but rather represent a collection of several related
technologies. At a bare minimum, any web service entails a
connection between two applicationsin programmers' parlance, a
remote procedure call (RPC)in which queries and responses are
exchanged in XML over HTTP. The more generally accepted
definition, however, implies implementation of a stack of
specific, complementary standards (see Figure 1, below).
Figure 1: The Web Services Technology Stack
Today, the core layers that define basic web services
communication have been widely accepted and likely will be
implemented quite uniformly. Higher-level layers that define
strategic aspects of business processes remain an open question,
however, and it is possible that divergent approaches will
The development of generally open and accepted standards is a
key strength of the coalitions that have been building web
services infrastructure. At the same time, these efforts have
resulted in a dizzying array of jargon and acronyms. We have
provided high-level descriptions of the most important ones
Core Layers of the Web Services Stack
- Common Internet Protocols. Although not
specifically tied to any transport protocol, web services
build on ubiquitous Internet connectivity and infrastructure
to ensure nearly universal reach and support. In particular,
web services will take advantage of HTTP, the same
connection protocol used by web servers and browsers.
- Extensible Markup Language (XML). XML is a widely
accepted format for exchanging data and its corresponding
semantics. It is a fundamental building block for nearly
every other layer in the web services stack.
- Simple Object Access Protocol (SOAP). SOAP is a protocol
for messaging and RPC-style communication between
applications. It is based on XML and uses common Internet
transport protocols like HTTP to carry its data. SOAP has
been submitted to the World Wide Web Consortium (W3C)
standards body and will emerge later this year as "XML
Higher-Level Layers of the Web Services Stack
- Web Services Description Language (WSDL). WSDL is an
XML-based description of how to connect to a particular web
service. A WSDL description abstracts a particular service's
various connection and messaging protocols into a high-level
bundle and forms a key element of the UDDI directory's
"green pages." IBM recently submitted WSDL to the W3C, and
it will likely be adopted in some form.
- Universal Description, Discovery, and Integration
(UDDI). UDDI represents a set of protocols and a public
directory for the registration and real-time lookup of web
services and other business processes. UDDI's sponsors,
chiefly IBM and Microsoft, officially released the first
public version of UDDI in May 2001. A few more revisions to
the specification are planned before UDDI is turned over to
a standards organization some time during the next 12
months. (For more information on UDDI, please see The
Stencil Group's recent report, "Why UDDI Will Succeed,
- Web Services Flow Language (WSFL). WSFL is the least
developed of the current web services layers. Sponsored by
IBM, the WSFL team hopes to define a framework that
implementers of web services can use to describe the
business logic required to assemble various services into an
end-to-end business process.
- Other Business Rules. Additional elements that support
complex business rules must still be implemented before web
services can automate truly critical business processes.
Indeed, we expect that mechanisms for security and
authentication, contract management, quality of service, and
more will soon followsome as standards, others as
value-added solutions from independent software vendors.
Other Related Technologies
- XML-RPC. XML-RPC represents the simplest form
of web service style connections. As the name indicates
(XML-RPC means "XML Remote Procedure Call"), the protocol
was a loosely-defined spin-off from the efforts that
ultimately led to the SOAP specification. Although not part
of the "classic" web services stack we define earlier in
this document, XML-RPC can be used in to achieve similar
benefits for less structured connections.
- ebXML. Efforts to define a standard XML format
for exchanging e-business related information predate the
recent rise of web services. Although sometimes presented as
an alternative to a web service model, ebXML is focused more
specifically on EDI-style information exchange. OASIS, the
group developing ebXML, recently adopted SOAP as a key
element of its specification, and we expect many businesses
will incorporate ebXML into their overall web services
strategies. ebXML was adopted by UN/CEFACT standards body in
Web Services FAQ
In the course of The Stencil Group's web services research, we
have heard a number of common questions raised in conversations,
at informational seminars, and in the press. We have addressed
some of these frequently asked questions below.
- What are web services?
- Web services are a group of closely related, emerging technologies that describe a service-oriented, component-based application architecture that is based on an open, Internet-centric infrastructure. Web services represent a model in which discrete tasks within e-business processes are distributed widely throughout a value net. Web services components can be recombined by other companies to meet the needs of their own software applications or business processes.
- What is an example of a web service?
- One simple example of a web service may be an auction engine like eBay's. The eBay web site offers a highly successful auction service. Today, however, if Widgets-R-Us, a business that sells surplus widgets, wants to add auction functionality to its own business model, it needs to develop its own auction software from scratch or redirect customers to a site like eBay. With web services, eBay could syndicate its auction functionality and make it available to other web sites or applications (presumably for a fee). Companies like Widgets-R-Us would simply subscribe to eBay's web service, add a few lines of code to their own applications to incorporate the web service, and they instantly have private-labeled auction functionality available on their own sites. Other customer-facing examples include stock quotes, content syndication, mapping services, and so on. Some more enterprise-centric services may include payroll management, shipping and logistics, business intelligence, credit scoring, etc.
- What are the technologies that make up web services?
- Web services are not a specific technology, but rather a group of established and emerging communication protocols that include HTTP, XML, Simple Object Application Protocol (SOAP), Universal Description Discovery and Integration (UDDI), and Web Services Description Language (WSDL). A web service can be developed on any computer platform and in any development environment, as long as it can communicate with other web services using these common protocols.
- How are web services different from earlier models of distributed computing?
- Web services draw extensively from previous models of component-based computing, including CORBA and others. The key differences are that web services are (1) loosely specified and coupled and (2) built on top of existing, ubiquitous infrastructure like HTTP and XML. Web services seem poised for success, because the technology's backers have, so far, focused on incremental technology changes and the mantra of "keep it simple."
- How is this different than EAI?
- Some applications of web services are related to the broad category of enterprise application integration (EAI) solutions. The differences are three-fold. First, EAI solutions link existing, monolithic applications into a common infrastructure, while web services are designed to allow for smaller, modular functionality that can be assembled and reassembled into dynamic processes. Second, most EAI technologies are designed to form discrete, pre-specified connections, while web services enable open-ended, one-to-many connections. Finally, EAI solutions' "all or nothing" models require a significant commitment of strategy and resources, while web services can be deployed with incremental cost and effort.
- Are web services a variation of the application service provider (ASP) model?
- Although ASPs and web services both implement the concept of "software as a service," the similarities end there. ASPs deliver entire applications from a central hosting location, while web services are distributed components. ASPs form a closed "black box," while web services are inherently extensible. ASPs are as much business model as technology solution; web services may enable new forms of business models, but are fundamentally a technology solution.
- Are web services a business model?
- Web services are not a business model. Although they will enable a shift in the way software companies deliver software and price software, web services are a model for technology development that is not limited to any particular business model
- Who developed the standards for web services?
- Web services represent a number of complementary (and sometimes coordinated) efforts by individual companies and coalitions of software vendors. Some of the web services protocols have been formally standardized by independent organizations like W3C. HTTP and XML are the existing foundation upon which DevelopMentor, UserLand Software, and Microsoft developed SOAP. After the initial SOAP specification, IBM and Ariba joined Microsoft to develop UDDI. IBM has since put its muscle behind a number of additional web services specifications, including WSDL, WSFL, and others.
- What companies are the major forces in web services?
- This is an open question. IBM and Microsoft have taken the early leadership mantle in establishing the web services stack. Hewlett-Packard, an early proponent of a proprietary services model, now is reorienting towards web services. Oracle, Sun, and a host of smaller companies (e.g. BEA, Bowstreet, and others) have also put hats into the ring.
- What are the relationships between web services and HP's NetAction, Microsoft's .NET, Sun ONE, etc.?
- Each of these labels represents the individual vendor's strategy and marketing efforts to establish a role for their products in the web services world. Some of these strategies clearly are articulated and developed, while others are little more than unspecified vision and "slideware" today.
IBM, "Web Services Architecture Overview"
Microsoft, "Web Services Essentials"
The Stencil Group, "How Web Services Will Beat 'The New New Thing' Rap"
The Stencil Group, "Why UDDI Will Succeed, Quietly"
XML.com, "A Web Services Primer"
For More Information
Exploring Web Services
web services research plan
web services article index
subscribe to the web services newsletter
participate in the web services survey
To learn more about The Stencil Group's web services focus, or
if you would like to participate in future memos, please explore
our research plan .
We are available to discuss this memo in more detail; please
contact us directly at (415) 615-0636 or
Copyright © 2001 The Stencil Group