Conclusion and Outlook - Enabling Semantic Web Services: The Web Service Modeling Ontology - page 167

12.4 Alternatives to Classical Web Services
Even if we have all appropriate semantic annotations in place and assume
that these are widely provided and used, there still remains an open question:
Are current Web service technologies the right means to achieve “Semantic
Web services”? Or, in other words how much “Web” is there in Web services?
Current technologies designed around WSDL and SOAP are not necessarily
the only starting point towards semantically enabled Web services [79].
A core paradigm of the Web is information exchange via persistent pub-
lication, i.e. one party publishes a piece of information on the Web, and any
other party who knows the location of the resource can retrieve and process the
information at any later point in time, without the need for synchronization
with the original publisher. This functionality has significantly contributed to
the scalability of the Web, since it reduced the amount of interaction between
the sender and the recipient.
Current Web service technologies ignore this particularity to a large extent,
the “Web” components used are mainly the communication layer (HTTP)
and the message format (XML), and otherwise, Web service technology per
se is a tightly coupled message exchange. This is similar to the situation in
the pre-Web age, where one had to send an email message to a scientific
colleague, asking for a specific paper or piece of information. In the current
Web, used as an infrastructure for humans, this pattern of communication has
been widely replaced by persistent publication and asynchronous retrieval.
The shift from information dissemination based on message exchange has not
only made the Web scale tremendously, it has also sped up the dissemination
process. When we compare Web services with this important principle of the
Web, it becomes evident that Web services per se do not follow this core idea.
The idea of publishing data and accessing it asynchronously is lacking. Instead
of publishing the information on the basis of a global, persistent URI, Web
services establish (1) stateful conversations based on (2) the hidden content
of messages.
The negative effect of such distributed applications that communicate via
message exchange is that they require a strong coupling in terms of reference
and time. This means that traditional Web services require that the sender
and receiver of data (1) maintain a connection at the same time, (2) agree
on the data format, and (3) know each other and share a common repre-
sentation. Therefore, the communication has to be directed to a particular
service and is synchronous as long as neither party implements asynchronous
communication.
The above line of argument is in alignment with the worries expressed by
the REST 4 community [42, 136]. The two major criticisms of Web services
are about the improper usage of URIs and the violation of the stateless ar-
4 REST stands for Representational State Transfer, a term coined by Roy Fielding
in his Ph.D. dissertation [42].