A URI (Uniform Resource Identifier) is a sequence of characters that identifies a logical QF physical resource. Universal Resource Identifiers are specified in the Internet Engineering Task Force (IETF) Request for Comments (RFC) 3986 and are summarized and extended in the documentation for the W3C's Web Architecture, Architecture of the World Wide Web. Volume L The URI describes the mechanism used to access resources, the computers on which resources are housed, and the names of the resources on each computer. There are two types of URIS, as follows: 

  1. Uniform Resource Locator (URL): This form of URI starts by expressing which protocol should be used to locate and access the physical or logical resource on a network. If the resource is a web page, for example, the URI will begin with the protocol HTTP. If the resource is a file, the URI will begin with the protocol FTP or if the resource is an email address, the URI will begin with the protocol mailto. it is obvious that URLs are not constant. So we can understand that if the resource's location changes, the URL also needs to change to point to the resource's new location, Every RwRL is also a URI, but not vice versa. 
  2. Uniform Resource Name (URN): This form of URI does not express a protocol that should be used to locate and access the resource, it simply labels the resource with a persistent, location-independent unique identifier. A URN will analyze the resource throughout its lifecycle and will never change. Each URN has three components: the label "urn," a colon, and a character string that serves as a unique identifier. 

URI Syntax 

The generic form of URI is 

Scheme: [/[User: password@] host [: Port][ Path [?query][#frament] 

  • Scheme: Schemes are case-insensitive and are followed by a colon. The scheme gives the particular syntax and syntax and any associated protocols for the URI, URI schemes should be registered with the Internet Assigned Numbers Authority (IANA), although non-registered schemes can also be used. In this example, two slashes are required by some schemes but they are not required by all schemes, including the authority component.
  • Authority Component: An authority component is constructed through multiple constraints, an optional authentication section, a host - consisting of either a registered name or an lP address -- and an optional port number. The authentication consists of the username and password, which are separated by a colon and followed by the symbol at (@). After the @ comes the hostname, which is in turn followed by a colon and then a port number. The thing is to remember that IPV4 addresses must be in dot-decimal notation, and IPV6 addresses must be enclosed in brackets. 
  • The path, which contains data, is described by a sequence of segments separated by slashes. The path must begin with a single slash if an authority part was present. It may also begin with a single slash even if there is no authority part, but it cannot begin with a double slash. 
  • Query (optional): The query accommodates a string of non-hierarchical data. Although 10the syntax is not well-defined, it is most often a sequence of attribute-value pairs separated by a delimiter, such as an ampersand or a semicolon. The query is separated from the preceding part by a question mark. 
  • Fragment (optional): The fragment contains a fragment identifier that provides direction to a secondary resource, For example if the primary resource is an HTML document, but the fragment is often an ID attribute of a specific element of that document. If the fragment log identifies a certain section of an article identified by the rest of the URI, a Web browser gan will scroll this particular element into view. The fragment is separated from the preceding part by a hash (#). 

URI Resolution and References 

URI resolution is one of a few common operations performed on URIS that are also URLs. It provides the proper data access method and parameters needed to locate and retrieve the resource that the URI points to. A URI reference is used to facilitate the common usage of a URI. A URI reference may take the form of a full URI, a specific portion of a full URI, or an empty string. If there is a fragment identifier, it will identify some portion of the resource referred to by the rest of the URI. A URI reference can be a URI, but it can also be what is known as a relative reference. A URI is a relative reference if the URI- reference's prefix does not match the syntax of a scheme followed by its colon separator. In order to determine what components are present and whether the reference is relative, each of the five URI components is parsed for its subparts and their validation.

Identifiers 

In the IoT standard, identifiers are divided into the following categories: object identifier. communication identifier, and application identifier. Object identifiers identify physical virtual objects. Barcodes and Radio Frequency IDentifier (RFID) are some examples of identifiers that cannot be used for addressing or communicating. Communication identifiers uniquely identify nodes on a network having communication capabilities, Any sensor network device is an example of a network node. The Communication identifier is com of an IP address and is used for addressing. Application identifiers identify service t applications, objects, logical entities, etc. Uniform Resource Identifier (URI) and Unif Resource Locator (URL) are some examples of application identifiers. 

Furthermore, to communicate with IoT applications running on different IoT platforms a unified identification methodology is needed. The distinct description nature of the hardware devices of different IoT platforms makes it even more difficult for them into working with heterogeneous identifiers. There are various universal ISs, such as Obic IDentifier (OID), Electronic Product Code (EPC), Universally Unique IDentifier (UUID and International Mobile Equipment Identity (IMEI), etc. These ISs are used in identifying objects or devices in different domains, such as the supply chain, cellular phones, and information systems.

Now it is very obvious to clear the difference between an identifier. So we first need to understand the distinction between the identifier of an object and its network address. The identifiers of an object and its network address are different and serve different purposes. The former provides a unique meaning to the object, whereas the latter might change with the physical location of the object. In the case where the address of the object differs from the identifier, the identifier is generated by using different IPs. The EPC is one of the well-known ISs that uniquely identifies an object associated with an RFID tag. 

An IoT is based on the interpretation of providing management, maintenance, and mapping discovery of identifiers and the retrieval of identifier information. A primary approach to a unified scheme or inter-working mechanism is to understand the various ISs that are used by IoT platforms. 

OID 

The OID is an identification mechanism developed by the ITU-T (International Telecommunication Union Telecommunication Standardization Sector) and the ISO/IEC (International Organization for Standardization/International Electrotechnical Commission), to name specific objects so that the objects can be determined. Based on the hierarchical name structure, objects are regulated as a sequence of base integer values and corresponding Unicode values so that they can be identified. The OID schemes enforce a hierarchy to assign unique numbers to objects so that they are not duplicated. Root has no name. It bas only 3 top-level areas which are managed by ISO. O is the ITU-T, I is the ISO, and 2 is jointly managed by the ISO and ITU-T. 

In the OlD hierarchy, each digit is called an are. The first is performing the managing organization, and 0 performs the ITU-T. The second is performing the type for which it is used. In this example, 2 represents the administration, The third arc is the Data Country Code DCC), which is assigned to cach country. In Korea, 450, 480, and 481 codes are assigned, and KISA is responsible for the management. 450 is used to discriminate the RFID code Dpe. These days, the other two numbers are not used, but the number I of 481 is experimentally granted and used by SKT. The fifth is 999 means the grant for the IoT, and the sixth are means the given organization or company. 

uniform resource identifier URI - OID structure
Fig. OID structure

The OID can be used in distinct fields, like Internet management, security, medical care, and RFID. It can recognize objects that are managed by the Internet. It can also be used for digital signature certificate items used by banks or various security duties to manage them efficiently and safely. In the field of RFID, unique identification methods are urgently needed. RFID, EPC, and ISO codes are used for existing barcodes. Therefore, special identification methods are needed for the new RFID service to avoid collision with the system that uses previous code systems, such as the EPC. Based on these reasons, the concept of OID is essential in RFID. 

EPC

An EPC is a universal identifier that assigns the identity to any physical object that is unique amongst all objects and categories all around the world, These unique identifiers are used to track objects in information systems that are part of the EPCglobal Network. EPCglek Inc facilitates overseeing the EPC standards, specifications, and guidelines for the auto It infrastructure to support its use. EPCglobal is a non-profit joint venture of GSI (formerly EAN International) and GSI US (formerly the Uniform Code Council). EPCglobal and other third-party providers aim to achieve a common goal towards an enhancement in business flows and computer applications through the use of EPCS.