BS ISO 24097-1:2009 Intelligent transport systems. Using web services (machine-machine delivery) for ITS service delivery. Realization of interoperable web services
This part of ISO 24097 establishes a Service-Oriented Architecture (SOA) for the realization of interoperable Intelligent Transport Systems (ITS) web services (WS). Web service behaviour is described at the metadata level (i.e. a higher level of abstraction) to enable auto-generation of both a “Service requestor” program, as well as a “Service provider” program.
The principal entities involved in a web service scenario are “Service provider“, “Service requestor” and “Registry”. The registry includes business information and technical information such as interface and policy. A service provider interacts with the registry to enable it to “publish” the service he/she is able to provide. The service is characterized by a web service interface describer in the form of a standardized web service description language (WSDL) and policy (WS-Policy). A service requestor interacts with the registry to “discover” a provider for the service he/she is seeking. That interaction takes place through Universal Description Discovery and Integration (UDDI) dialogue and endpoint reference (EPR). Once the service requestor identifies a service provider, he “binds” to the service provider via an SOA protocol.
This part of ISO 24097 is applicable to inter-ITS sector WS, as well as ITS WS for non-ITS users.
Intelligent Transport Systems (ITS) services have been evolving from single functional and limited area specific services, to a broad range of services in which many systems cooperate to provide effective and efficient service provision across a wide area. In today’s world, ITS services are required to communicate not just with other parts of the same ITS service provision, but between different ITS services and even with non-ITS services or a user’s system directly. Some examples of these systems are communications between traffic management, route guidance systems, homeland security systems, environment protection systems and private freight management systems.
These systems (even those limited to ITS services) are usually deployed in a heterogeneous circumstance, use different hardware, different operating system (OS), middleware, or development languages. This therefore creates a challenge in order to realize system coordination across the organizations in a way that is flexible, quick and at reasonable cost. Web services (WS) are a recent methodology that overcomes these difficulties. Using web service technology for ITS services can significantly simplify and reduce the cost of Internet-based service provision, which can affect the level and speed of take up of use of ITS services.
The World Wide Web Consortium (W3C) defines WS as follows: “A web service is a software system designed to support interoperable machine-machine interaction over a network. It has an interface described in a machine-processable format [specifically WSDL (Web Services Description Language)]. Other systems interact with the web service in a manner prescribed by its description using SOAP-messages, typically conveyed using HTTP with an XML serialization in conjunction with other web-related standards.”
WS require quite a lot of functionalities and as a result, an architecture is indispensable. Web service standardization organizations construct standards by Service-Oriented Architecture (SOA). SOA is an evolutional form of distributed computing and object orientation.
By applying SOA-based standards to ITS services, the following effects are expected:
From a business viewpoint
- Increased service value
- Internationalization
- Expansion towards business automation.
From a system development perspective:
- Easy and quick development of ITS service coordination and service area expansion
- WS enable system developers to focus on the “what” not the “how.” “HOW” is covered by standard base tools. This enables quick and easy system software development
- Composable structure of web service standards promote reusability of software
- Easy connection to a legacy system.
In the ITS sector, message standardization of many applications has already been completed, are well advanced, or are determined regionally. Message standardization is intended to improve system coordination, interoperability and re-use and so the conditions for WS are considered already mature. In addition, the use of WS will increase the flexibility of ITS services to interoperate and communicate beyond the ITS sector and in areas where the delineation between ITS services and general commercial services converge.
From the perspective of the evolution of standards in WS, 2007 was an epoch-making year. WSDL 2.0 became the W3C recommendation. Correspondingly, relevant web service specifications were standardized by open standardization bodies (W3C and OASIS). These standards cover all functional layers. In using these standards, the ITS sector has a rigid base for interoperable WS.
ITS service collaboration with other sectors is expected to increase mutual effectiveness. Economic globalization also requires communication across the country, often across the world. All of these collaborations rely on interoperability of services. Interoperability is only achieved based on open international standards.
WS were developed to use distributed network resources in an interoperable way. However, to realize interoperable WS, various functionalities are required. ISO 24097 (all parts) has been developed based on these circumstances.
Contents of BS ISO 24097-1 include:- Scope
- Conformance
- Normative references
- Terms, definitions and abbreviated terms
- Notation
- Prefixes and namespace URI used in core specification
- Web service syntax notation : BNF pseudo-schemas
- XPath 1.0 notation
- Notation of service provider, service consumer combination
- SOA stack name notation
- Set notation
- Tentative IRI expression
- Rnnnn (nnnn: digits integer)
- Requirements
- Basic concept of web services standardization
- Web service metadata
- Service description layer
- Quality of service layer
- Messaging layer — Requirements and recommendations for XML messaging
- Service publication/discovery layer
- Service publication/discovery layer — requirements and recommendations for universal description, discovery and integration
- Principles and evolution of WSDL from Version 1.1 to
- WDSL syntax
- Bibliography
