The term web service is either a service offered by an electronic device to another electronic device, communicating with each other via the World Wide Web, or a web service implemented in the particular technology or brand, e.g W3C Web Services. In a web service, the Web technology such as HTTP—originally designed for human-to-machine communication—is utilized for machine-to-machine communication, more for transferring machine-readable file formats such as XML and JSON. In practice, a web service provides an object-oriented web-based interface to a database server, utilized for example by another web server, or by a mobile app, that provides a user interface to the end user. Many organizations that provide data in formatted HTML pages will provide that data on their server as XML or JSON through a web service to allow syndication, for example Wikipedia's Export. Another application offered to the end user may be a mashup, where a web server consumes several web services at different machines, compiles the content into one user interface.
Restful APIs do not require XML-based web service protocols to support their interfaces. In relation to W3C Web Services, the W3C defined a web service as: A web service is a software system designed to support interoperable machine-to-machine interaction over a network, it has an interface described in a machine-processable format. Other systems interact with the web service in a manner prescribed by its description using SOAP-messages conveyed using HTTP with an XML serialization in conjunction with other web-related standards. W3C Web Services may use SOAP over HTTP protocol, allowing less costly interactions over the Internet than via proprietary solutions like EDI/B2B. Besides SOAP over HTTP, web services can be implemented on other reliable transport mechanisms like FTP. In a 2002 document, the Web Services Architecture Working Group defined a web services architecture, requiring a standardized implementation of a "web service." The term "web service" describes a standardized way of integrating web-based applications using the XML, SOAP, WSDL and UDDI open standards over an Internet Protocol backbone.
XML is the data format used to contain the data and provide metadata around it, SOAP is used to transfer the data, WSDL is used for describing the services available and UDDI lists what services are available. A web service is a method of communication between two electronic devices over a network, it is a software function provided at a network address over the web with the service always on as in the concept of utility computing. Many organizations use multiple software systems for management. Different software systems need to exchange data with each other, a web service is a method of communication that allows two software systems to exchange this data over the internet; the software system that requests data is called a service requester, whereas the software system that would process the request and provide the data is called a service provider. Different software may use different programming languages, hence there is a need for a method of data exchange that doesn't depend upon a particular programming language.
Most types of software can, interpret XML tags. Thus, web services can use XML files for data exchange. Rules for communication between different systems need to be defined, such as: How one system can request data from another system. Which specific parameters are needed in the data request. What would be the structure of the data produced. What error messages to display when a certain rule for communication is not observed, to make troubleshooting easier. All of these rules for communication are defined in a file called WSDL. A directory called. So when one software system needs one particular report/data, it would go to the UDDI and find out which other system it can contact for receiving that data. Once the software system finds out which other system it should contact, it w
A Controller Area Network is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a host computer. It is a message-based protocol, designed for multiplex electrical wiring within automobiles to save on copper, but is used in many other contexts. Development of the CAN bus started in 1983 at Robert Bosch GmbH; the protocol was released in 1986 at the Society of Automotive Engineers conference in Detroit, Michigan. The first CAN controller chips, produced by Intel and Philips, came on the market in 1987. Released in 1991 the Mercedes-Benz W140 was the first production vehicle to feature a CAN-based multiplex wiring system. Bosch published several versions of the CAN specification and the latest is CAN 2.0 published in 1991. This specification has two parts. A CAN device that uses 11-bit identifiers is called CAN 2.0A and a CAN device that uses 29-bit identifiers is called CAN 2.0B. These standards are available from Bosch along with other specifications and white papers.
In 1993, the International Organization for Standardization released the CAN standard ISO 11898, restructured into two parts. ISO 11898-3 was released and covers the CAN physical layer for low-speed, fault-tolerant CAN; the physical layer standards ISO 11898-2 and ISO 11898-3 are not part of the Bosch CAN 2.0 specification. These standards may be purchased from the ISO. Bosch is still active in extending the CAN standards. In 2012, Bosch released CAN with Flexible Data-Rate; this specification uses a different frame format that allows a different data length as well as optionally switching to a faster bit rate after the arbitration is decided. CAN FD is compatible with existing CAN 2.0 networks so new CAN FD devices can coexist on the same network with existing CAN devices. CAN bus is one of five protocols used in the on-board diagnostics -II vehicle diagnostics standard; the OBD-II standard has been mandatory for all cars and light trucks sold in the United States since 1996. The EOBD standard has been mandatory for all petrol vehicles sold in the European Union since 2001 and all diesel vehicles since 2004.
Passenger vehicles, buses Electronic equipment for aviation and navigation Industrial automation and mechanical control Elevators, escalators Building automation Medical instruments and equipment The modern automobile may have as many as 70 electronic control units for various subsystems. The biggest processor is the engine control unit. Others are used for transmission, antilock braking/ABS, cruise control, electric power steering, audio systems, power windows, mirror adjustment and recharging systems for hybrid/electric cars, etc; some of these form independent subsystems. A subsystem may need to receive feedback from sensors; the CAN standard was devised to fill this need. One key advantage is that interconnection between different vehicle systems can allow a wide range of safety and convenience features to be implemented using software alone - functionality which would add cost and complexity if such features were "hard wired" using traditional automotive electrics. Examples include: Auto start/stop: Various sensor inputs from around the vehicle are collated via the CAN bus to determine whether the engine can be shut down when stationary for improved fuel economy and emissions.
Electric park brakes: The "hill hold" functionality takes input from the vehicle's tilt sensor and the road speed sensors via the CAN bus to determine if the vehicle is stopped on an incline. Inputs from seat belt sensors are fed from the CAN bus to determine if the seat belts are fastened, so that the parking brake will automatically release upon moving off. Parking assist systems: when the driver engages reverse gear, the transmission control unit can send a signal via the CAN bus to activate both the parking sensor system and the door control module for the passenger side door mirror to tilt downward to show the position of the curb; the CAN bus takes inputs from the rain sensor to trigger the rear windscreen wiper when reversing. Auto lane assist/collision avoidance systems: The inputs from the parking sensors are used by the CAN bus to feed outside proximity data to driver assist systems such as Lane Departure warning, more these signals travel through the CAN bus to actuate brake by wire in active collision avoidance systems.
Auto brake wiping: Input is taken from the rain sensor via the CAN bus to the ABS module to initiate an imperceptible application of the brakes whilst driving to clear moisture from the brake rotors. Some high performance Audi and BMW models incorporate this feature. Sensors can be placed at the most suitable place, its data used by several ECU. For example, outdoor temperature sensors can be placed in the outside mirrors, avoiding heating by the engine, data used by both the engine, the climate control and the driver display. In recent years, the LIN bus standard has been introduced to complement CAN for non-critical subsystems such as air-conditioning and infotainment, where data transmis
Hypertext Transfer Protocol
The Hypertext Transfer Protocol is an application protocol for distributed, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, where hypertext documents include hyperlinks to other resources that the user can access, for example by a mouse click or by tapping the screen in a web browser. HTTP was developed to facilitate the World Wide Web. Development of HTTP was initiated by Tim Berners-Lee at CERN in 1989. Development of HTTP standards was coordinated by the Internet Engineering Task Force and the World Wide Web Consortium, culminating in the publication of a series of Requests for Comments; the first definition of HTTP/1.1, the version of HTTP in common use, occurred in RFC 2068 in 1997, although this was made obsolete by RFC 2616 in 1999 and again by the RFC 7230 family of RFCs in 2014. A version, the successor HTTP/2, was standardized in 2015, is now supported by major web servers and browsers over Transport Layer Security using Application-Layer Protocol Negotiation extension where TLS 1.2 or newer is required.
HTTP functions as a request–response protocol in the client–server computing model. A web browser, for example, may be the client and an application running on a computer hosting a website may be the server; the client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content, or performs other functions on behalf of the client, returns a response message to the client; the response contains completion status information about the request and may contain requested content in its message body. A web browser is an example of a user agent. Other types of user agent include the indexing software used by search providers, voice browsers, mobile apps, other software that accesses, consumes, or displays web content. HTTP is designed to permit intermediate network elements to improve or enable communications between clients and servers. High-traffic websites benefit from web cache servers that deliver content on behalf of upstream servers to improve response time.
Web browsers cache accessed web resources and reuse them, when possible, to reduce network traffic. HTTP proxy servers at private network boundaries can facilitate communication for clients without a globally routable address, by relaying messages with external servers. HTTP is an application layer protocol designed within the framework of the Internet protocol suite, its definition presumes an underlying and reliable transport layer protocol, Transmission Control Protocol is used. However, HTTP can be adapted to use unreliable protocols such as the User Datagram Protocol, for example in HTTPU and Simple Service Discovery Protocol. HTTP resources are identified and located on the network by Uniform Resource Locators, using the Uniform Resource Identifiers schemes http and https. URIs and hyperlinks in HTML documents form interlinked hypertext documents. HTTP/1.1 is a revision of the original HTTP. In HTTP/1.0 a separate connection to the same server is made for every resource request. HTTP/1.1 can reuse a connection multiple times to download images, stylesheets, etc after the page has been delivered.
HTTP/1.1 communications therefore experience less latency as the establishment of TCP connections presents considerable overhead. The term hypertext was coined by Ted Nelson in 1965 in the Xanadu Project, in turn inspired by Vannevar Bush's 1930s vision of the microfilm-based information retrieval and management "memex" system described in his 1945 essay "As We May Think". Tim Berners-Lee and his team at CERN are credited with inventing the original HTTP, along with HTML and the associated technology for a web server and a text-based web browser. Berners-Lee first proposed the "WorldWideWeb" project in 1989—now known as the World Wide Web; the first version of the protocol had only one method, namely GET, which would request a page from a server. The response from the server was always an HTML page; the first documented version of HTTP was HTTP V0.9. Dave Raggett led the HTTP Working Group in 1995 and wanted to expand the protocol with extended operations, extended negotiation, richer meta-information, tied with a security protocol which became more efficient by adding additional methods and header fields.
RFC 1945 introduced and recognized HTTP V1.0 in 1996. The HTTP WG planned to publish new standards in December 1995 and the support for pre-standard HTTP/1.1 based on the developing RFC 2068 was adopted by the major browser developers in early 1996. By March that year, pre-standard HTTP/1.1 was supported in Arena, Netscape 2.0, Netscape Navigator Gold 2.01, Mosaic 2.7, Lynx 2.5, in Internet Explorer 2.0. End-user adoption of the new browsers was rapid. In March 1996, one web hosting company reported that over 40% of browsers in use on the Internet were HTTP 1.1 compliant. That same web hosting company reported that by June 1996, 65% of all browsers accessing their servers were HTTP/1.1 compliant. The HTTP/1.1 standard as defined in RFC 2068 was released in January 1997. Improvements and updates to the HTTP/1.1 standard were released under RFC 2616 in June 1999. In 2007, the HTTPbis Working Group was formed, in part, to revise and clarify the HTTP/1.1 specification. In June 2014, the WG released an updated six-part specification obsoleting RFC 2616: RFC 7230, HTTP/1.1: Message Syntax and Routing RFC 7231, HTTP/1.1: Semantics and Content RFC 7232, HTTP/1.1: Conditional Requests RFC 7233, HTTP/1.1: Range Requests RFC 7234, HTTP/1.1: Caching RFC 7235, HTTP/1