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Fig. 1 Blackbox overview of Weda
endpoints and binding while keeping their HTTP server endpoints to legacy clients
alongside Weda endpoints (Fig.
1
).
New possibilities grew with the arrival of Websockets. Websockets is a tech-
nology that provides bi-directional, full duplex communication over a single TCP
socket. It is designed to be implemented in web browsers and web servers and
traverses
firewalls, proxies, and routers seamlessly and leverages Cross-Origin
Resource Sharing (CORS). The communication channel can be protected against
eaves-dropping with TLS, much like HTTPS. The default ports are 80 or 443, so
enterprises are not required to open additional ports in their
firewalls.
2.1 Comparison of Web Services Architectural Styles
We can identify three classes of Web services (Table
1
):
REST-compliant Web services, in which the primary purpose of the service is to
manipulate XML representations of Web resources using a uniform set of
“
stateless
”
operations.
RPC-compliant Web services, in which the service may expose an arbitrary set
of operations.
WEDA-compliant Web services, in which the service can use asynchronous
message passing which can provide us eventing behaviour as well as call and
return.
We developed an informal (IANA or RPC based) [
8
] as well as a formal (timed
automata) speci
cation [
9
], whose purpose is to ensure the interoperability between
Weda implementers. The list of topics covered is: Weda gateway, Weda endpoints
(also for non-public client endpoints), Addressing, Weda transport binding, Con-
tracts, Weda subprotocol, Weda service description, model checking and veri
ca-
tion. All of the components were implemented into the beta version of Weda API.
The aim of future development is to provide an easily pluggable library in more
programming languages, which has a simple interface but robust and self-contained
implementation.
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