I-number
Encyclopedia
i-numbers are a type of Internet
identifier designed to solve the problem of how any resource
can have a persistent identity that never changes even when the resource moves or changes its human-friendly name. For example, if a Web page
has an i-number, and links to that page use the i-number, then those links will not break even if the page is renamed, the website containing the page is complete reorganized, or the page is moved to another website.
Conceptually, an i-number is similar to an IP address
, except i-numbers operate at a much higher level of abstraction
in Internet addressing architecture. But the other key difference between the two is that i-numbers are persistent, i.e., once they are assigned to a resource, they are never reassigned. By contrast, IP addresses are constantly reassigned, i.e., your computer may have a different IP address every time it connects to the Internet.
Technically, an i-number is one form of an Extensible Resource Identifier
(XRI) — an abstract structured identifier standard developed at Organization for the Advancement of Structured Information Standards for sharing resources and data across domains and applications. The other form is called an i-name
.
The i-number form of an XRI is designed to serve as an address that does not need to change no matter how often the location of a resource on (or off) the Internet changes. XRIs accomplish this by adding a third layer of abstract addressing over the existing layers: IP
numbering (first layer) and DNS
naming (second layer). The notion of a third layer for persistent addressing is not new — URN
s (Uniform Resource Names) and other persistent identifier architectures have been developed for this purposes. However the XRI layer is the first architecture that combines a uniform syntax and resolution protocol for both persistent and reassignable identifiers.
At the XRI addressing layer, most resources will have both i-names and i-numbers. These different XRIs that all point to the same resource are called synonyms. I-name synonyms make it easy for humans to discover and address the resource, while i-number synonyms make it easy for machines to maintain a persistent identity for the resource. For example, if a company changes its name, it may register a new i-name and sell its old i-name to another company, however its i-number can remain the same — and links to the company that use its i-number won't break.
Furthermore, all of these forms of XRI synonyms can be resolved using the same http- or https-based resolution protocol. The results of XRI resolution are an XML
document called an XRDS (Extensible Resource Descriptor Sequence). XRDS documents are the basis for the Yadis
identity service discovery protocol that is now part of OpenID
.
XRIs are also backwards compatible with the DNS and IP addressing systems, so it is possible for domain names and IP addresses to be used as i-names (or, in rare cases, as i-numbers). Like DNS names, XRIs can also be delegated, i.e., nested multiple levels deep, just like the directory names on a local computer file system. For example, a company can register a top-level (global) i-name and i-number for itself, and then assign second- or lower-level (community) i-names and i-numbers to its divisions, employees, etc.
Global I-Numbers
Community i-numbers (second-level)
Community i-numbers (third-level)
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
identifier designed to solve the problem of how any resource
Resource (Web)
The concept of resource is primitive in the Web architecture, and is used in the definition of its fundamental elements. The term was first introduced to refer to targets of Uniform Resource Locators , but its definition has been further extended to include the referent of any Uniform Resource...
can have a persistent identity that never changes even when the resource moves or changes its human-friendly name. For example, if a Web page
Web page
A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...
has an i-number, and links to that page use the i-number, then those links will not break even if the page is renamed, the website containing the page is complete reorganized, or the page is moved to another website.
Conceptually, an i-number is similar to an IP address
IP address
An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...
, except i-numbers operate at a much higher level of abstraction
Abstraction (computer science)
In computer science, abstraction is the process by which data and programs are defined with a representation similar to its pictorial meaning as rooted in the more complex realm of human life and language with their higher need of summarization and categorization , while hiding away the...
in Internet addressing architecture. But the other key difference between the two is that i-numbers are persistent, i.e., once they are assigned to a resource, they are never reassigned. By contrast, IP addresses are constantly reassigned, i.e., your computer may have a different IP address every time it connects to the Internet.
Technically, an i-number is one form of an Extensible Resource Identifier
Extensible Resource Identifier
Extensible Resource Identifier is a scheme and resolution protocol for abstract identifiers compatible with Uniform Resource Identifiers and Internationalized Resource Identifiers, developed by the at OASIS...
(XRI) — an abstract structured identifier standard developed at Organization for the Advancement of Structured Information Standards for sharing resources and data across domains and applications. The other form is called an i-name
I-name
I-names are one form of an XRI — an OASIS open standard for digital identifiers designed for sharing resources and data across domains and applications. I-names are human readable XRIs intended to be as easy as possible for people to remember and use. For example, a personal i-name could be =Mary...
.
The i-number form of an XRI is designed to serve as an address that does not need to change no matter how often the location of a resource on (or off) the Internet changes. XRIs accomplish this by adding a third layer of abstract addressing over the existing layers: IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
numbering (first layer) and DNS
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...
naming (second layer). The notion of a third layer for persistent addressing is not new — URN
URN
An urn is a vase-like container.Urn or URN may also refer to:*Uniform Resource Name, a subset of URI*User Requirements Notation, an ITU-T standard*University Radio Nottingham, a university radio station in Nottingham, England...
s (Uniform Resource Names) and other persistent identifier architectures have been developed for this purposes. However the XRI layer is the first architecture that combines a uniform syntax and resolution protocol for both persistent and reassignable identifiers.
At the XRI addressing layer, most resources will have both i-names and i-numbers. These different XRIs that all point to the same resource are called synonyms. I-name synonyms make it easy for humans to discover and address the resource, while i-number synonyms make it easy for machines to maintain a persistent identity for the resource. For example, if a company changes its name, it may register a new i-name and sell its old i-name to another company, however its i-number can remain the same — and links to the company that use its i-number won't break.
Furthermore, all of these forms of XRI synonyms can be resolved using the same http- or https-based resolution protocol. The results of XRI resolution are an XML
Extensible Markup Language
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
document called an XRDS (Extensible Resource Descriptor Sequence). XRDS documents are the basis for the Yadis
Yadis
Yadis is a communications protocol for discovery of services such as OpenID, OAuth, and XDI connected to a Yadis ID. While intended to discover digital identity services, Yadis is not restricted to those. Other services can easily be included....
identity service discovery protocol that is now part of OpenID
OpenID
OpenID is an open standard that describes how users can be authenticated in a decentralized manner, eliminating the need for services to provide their own ad hoc systems and allowing users to consolidate their digital identities...
.
XRIs are also backwards compatible with the DNS and IP addressing systems, so it is possible for domain names and IP addresses to be used as i-names (or, in rare cases, as i-numbers). Like DNS names, XRIs can also be delegated, i.e., nested multiple levels deep, just like the directory names on a local computer file system. For example, a company can register a top-level (global) i-name and i-number for itself, and then assign second- or lower-level (community) i-names and i-numbers to its divisions, employees, etc.
Examples
The following examples conform to the i-number specifications published in the XDI.org Global Services Specifications. Note that they do not include the xri:// prefix as this is optional with absolute XRIs.Global I-Numbers
- =!1000.a1b2.93d2.8c73 (Personal)
- @!1000.9554.fabd.129c (Organizational)
- !!1000 (Network — reserved for XDI.org-accredited i-brokerI-brokerAn i-broker is a "banker for data" or "ISP for identity services" — a trusted third party that helps individuals and organizations share private data the same way banks help exchange funds and ISPs help exchange e-mail and files. The term was introduced in the Social Web paper describing how a new...
s)
Community i-numbers (second-level)
- =!1000.a1b2.93d2.8c73!3ae2 (Personal)
- @!1000.9554.fabd.129c!2847.df3c (Organizational)
- !!1000!de21.4536.2cb2.8074 (Network)
Community i-numbers (third-level)
- =!1000.a1b2.93d2.8c73!3ae2!1490 (Personal)
- @!1000.9554.fabd.129c!2847.df3c!cfae (Organizational)
- !!1000!de21.4536.2cb2.8074!9fcd (Network)
See also
- Global context registriesGlobal context registriesGlobal context registries are a simple, human-friendly way to indicate the global context of an i-name or i-number. There are three key types of global context registries, each represented by a single symbol as shown.-See also:* I-broker...
- I-nameI-nameI-names are one form of an XRI — an OASIS open standard for digital identifiers designed for sharing resources and data across domains and applications. I-names are human readable XRIs intended to be as easy as possible for people to remember and use. For example, a personal i-name could be =Mary...
- I-brokerI-brokerAn i-broker is a "banker for data" or "ISP for identity services" — a trusted third party that helps individuals and organizations share private data the same way banks help exchange funds and ISPs help exchange e-mail and files. The term was introduced in the Social Web paper describing how a new...
- XRI (Extensible Resource Identifier)
- XDIXDIXDI is a generalized, extensible service for sharing, linking, and synchronizing structured data over the Internet and other data networks using XRI-addressable RDF graphs...
(XRI Data Interchange) - Social WebSocial WebThe social Web is a set of social relations that link people through the World Wide Web. The Social web encompasses how websites and software are designed and developed in order to support and foster social interaction. These online social interactions form the basis of much online activity...
- Zooko's triangleZooko's triangleZooko's triangle is a diagram named after Zooko Wilcox-O'Hearn which sets out the possible tradeoffs for a system for giving names to participants in a network protocol. At the vertices of the triangle are three properties that are generally considered desirable for such names:* Secure: The...