; While the primary concern for Roadrunner RF is compliance with traffic standards, such as the National Transportation Communications for ITS Projects (NTCIP) and thereby its parent organizations– AASHTO, ITE, and NEMA–other standards are driving the “Internet of Things,” which this class of device belongs to.
The precursor ‘technology’ for communication with industrial devices was SNMP, or Simple Network Management Protocols. The program would “walk the tree” to collect data. This required accessing the device through a specific port, sending complex octet strings and retrieving the same.
Roadrunner instead uses what are termed RESTful services. More information on what REST is all about is contained in the expandable section below.
var myLatestSpeed = myRoadrunnerSensor.latestSpeedl;
will return, for example, “45”.
The World Wide Web operates as a networked information system that imposes several constraints: Agents identify objects in the system, called resources, with Uniform Resource Identifiers (URIs). Agents represent, describe, and communicate resource state via representations of the resource in a variety of widely-understood data formats (e.g. XML, HTML, CSS, JPEG, PNG). Agents exchange representations via protocols that use URIs to identify and directly or indirectly address the agents and resources. [Web Arch]
An even more constrained architectural style for reliable Web applications known as Representation State Transfer(REST) has been proposed by Roy Fielding and has inspired both the W3C Technical Architecture Group’s architecture document [Web Arch] and many who see it as a model for how to build Web services [Fielding]. The REST Web is the subset of the WWW (based on HTTP) in which agents provide uniform interface semantics — essentially create, retrieve, update and delete — rather than arbitrary or application-specific interfaces, and manipulate resources only by the exchange of representations. Furthermore, the REST interactions are “stateless” in the sense that the meaning of a message does not depend on the state of the conversation.
We can identify two major classes of Web services:
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; and
arbitrary Web services, in which the service may expose an arbitrary set of operations.
Both classes of Web services use URIs to identify resources and use Web protocols (such as HTTP and SOAP 1.2) and XML data formats for messaging. (It should be noted that SOAP 1.2 can be used in a manner consistent with REST. However, SOAP 1.2 can also be used in a manner that is not consistent with REST.)
Rest services are easy to implement. No special toolkits are required to access the data. They are easy to integrate, too, as data is quickly and seamlessly available for use. No “dialing in” to the device to retrieve data. No parsing of strings, as the data are evaluated into dot-syntax objects. No complex insert or delete statements and database drivers required.
REST works with any system. No DCOM, no drivers, It is agnostic as to which ATMS system it informs. In fact, since most ATMS systems use C# all that is required is a data adapter and a dataset to convert the data into a fully formed, NTCIP compliant set of data tables.
4. NTCIP & TMDD
The following demonstrates the NTCIP and TMDD data structures: