--- title: Uniform Resource Identifiers TARGET DECK: Obsidian::STEM FILE TAGS: uri tags: - rdf - uri --- ## Overview A **uniform resource identifier** (URI) is a unique sequence of characters for identifying some physical or abstract resource. URIs are further generalized to **internationalized resource identifier**s (IRIs) which allow using characters from any language, provided there exists a standard web encoding of the characters. %%ANKI Basic What is URI an acronym for? Back: **U**niform **r**esource **i**dentifier. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic *Why* is a URI named the way it is? Back: It is a globally unique identifier for some resource. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic What is IRI an acronym for? Back: **I**nternationalized **r**esource **i**dentifier. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic In what way does an IRI generalize URIs? Back: It allows any characters with standard web encodings to be used in the identifier. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic Which of URIs or IRIs are more general? Back: IRIs. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% The URI generic syntax consists of five components organized hierarchically in order of decreasing significance from left to right: ``` :[//][?][#] ``` where the `` is further composed as ``` [@][:] ``` %%ANKI Cloze A URI has the following generic syntax: {``}`:`{`[//]`}{``}{`[?]`}{`[#]`}. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic Which two components of a URI are required? Back: The scheme and the path. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic Which three components of a URI are optional? Back: The authority, query, and fragment. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic How many top-level components make up a URI's generic syntax? Back: Five. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic What is the associated delimiter of a URI's authority? Back: `//` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic What is the associated delimiter of a URI's query? Back: `?` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic What is the associated delimiter of a URI's scheme? Back: N/A. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic What is the associated delimiter of a URI's fragment? Back: `#` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic What is the associated delimiter of a URI's path? Back: N/A. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic When is a URI's component considered "undefined"? Back: When its associated delimiter is not present in the URI. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic Which URI components are always defined? Back: The scheme and the path. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic What delimiter separates the segments of a path? Back: `/` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what scheme? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: `http` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what authority? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: `//www.example.com` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what userinfo? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what port? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what host? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: `www.example.com` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what path? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: `/questions/3456/my-document` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what query? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what fragment? $$\text{http://www.example.com/questions/3456/my-document}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Cloze The authority of a URI has the following generic syntax: {`[@]`}{``}{`[:]`} Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic Which two components of a URI's authority is optional? Back: The user info and port. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic Which component of a URI's authority is required? Back: The host. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what scheme? $$\text{ldap://[2001:db8::7]/c=GB?objectClass?one}$$ Back: `ldap` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what fragment? $$\text{ldap://[2001:db8::7]/c=GB?objectClass?one}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what authority? $$\text{ldap://[2001:db8::7]/c=GB?objectClass?one}$$ Back: `[2001:db8::7]` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what query? $$\text{ldap://[2001:db8::7]/c=GB?objectClass?one}$$ Back: `objectClass?one` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what path? $$\text{ldap://[2001:db8::7]/c=GB?objectClass?one}$$ Back: `/c=GB` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what scheme? $$\text{tel:+1-816-555-1212}$$ Back: `tel` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what authority? $$\text{tel:+1-816-555-1212}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what path? $$\text{tel:+1-816-555-1212}$$ Back: `+1-816-555-1212` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what query? $$\text{tel:+1-816-555-1212}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what fragment? $$\text{tel:+1-816-555-1212}$$ Back: N/A. It is undefined. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what scheme? $$\text{telnet://192.0.2.16:80/}$$ Back: `telnet` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what authority? $$\text{telnet://192.0.2.16:80/}$$ Back: `192.0.2.16:80` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic The following URI specifies what path? $$\text{telnet://192.0.2.16:80/}$$ Back: `/` Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% ### URLs A **uniform resource locator** (URL) is a URI that specifies the means of finding the represented resource. The most commonly used schemes are `http` and `https`. %%ANKI Basic What is URL an acronym for? Back: **U**niform **r**esource **l**ocator. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic *Why* is a URL named the way it is? Back: Its structure specifies how to find the corresponding resource. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic How do you find the resource represented by a URI? Back: N/A. This isn't generally possible. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic In what way does a URI generalize URLs? Back: A URI does not necessarily specify how to find the represented resource. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic Which of URIs or URLs are more general? Back: URIs. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic Which of IRIs or URLs are more general? Back: IRIs. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic What scheme are URLs required to use? Back: N/A. There exist many possible schemes. Reference: “Uniform Resource Locator.” In _Wikipedia_, June 20, 2024. [https://en.wikipedia.org/w/index.php?title=URL](https://en.wikipedia.org/w/index.php?title=URL&oldid=1230124093). END%% %%ANKI Basic What are the two most commonly used URL schemes? Back: `http` and `https`. Reference: “Uniform Resource Locator.” In _Wikipedia_, June 20, 2024. [https://en.wikipedia.org/w/index.php?title=URL](https://en.wikipedia.org/w/index.php?title=URL&oldid=1230124093). END%% ### URNs A **uniform resource name** (URN) is a URI that uses the `urn` scheme. It is intended to uniquely identify a resource, even when the resource no longer exists. %%ANKI Basic What is URN an acronym for? Back: **U**niform **r**esource **n**ame. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic *Why* is a URN named the way it is? Back: It is used to uniquely identify some resource. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic Which of URLs or URNs are more general? Back: N/A. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic Which of URNs or URIs are more general? Back: URIs. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic *Why* aren't URLs a subset of URNs? Back: What a URL represents may change over time. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic *Why* aren't URNs a subset of URLs? Back: Their structure may not necessarily indicate how to find the resource. Reference: “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). END%% %%ANKI Basic What scheme are URNs required to use? Back: `urn` Reference: “Uniform Resource Name.” In _Wikipedia_, April 26, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Name](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Name&oldid=1220954593). END%% ## CURIEs A **compact URI** (CURIE) is a denser representation of URIs. In its simplest form, it consists of a namespace and identifier separated by a colon. For example, `geo:England`. %%ANKI Basic URIs in RDF are usually represented in what condensed format? Back: CURIEs. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic What is CURIE an acronym for? Back: **C**ompact **URI**s. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic Consider CURIE `geo:England`. What is `geo` an example of? Back: A namespace. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic Consider CURIE `geo:England`. What is `England` an example of? Back: An identifier. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic In its simplest form, a CURIE is made up of what two parts? Back: A namespace and an identifier. Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% %%ANKI Basic The namespace and identifier of a CURIE is usually separated by what? Back: A colon (`:`). Reference: Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. END%% ## Bibliography * Allemang, Dean, James A. Hendler, and Fabien L. Gandon. _Semantic Web for the Working Ontologist_. 3e ed. ACM Books 33. New York: Association for computing machinery, 2020. * “Uniform Resource Identifier.” In _Wikipedia_, July 22, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Identifier&oldid=1235957234). * “Uniform Resource Locator.” In _Wikipedia_, June 20, 2024. [https://en.wikipedia.org/w/index.php?title=URL](https://en.wikipedia.org/w/index.php?title=URL&oldid=1230124093). * “Uniform Resource Name.” In _Wikipedia_, April 26, 2024. [https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Name](https://en.wikipedia.org/w/index.php?title=Uniform_Resource_Name&oldid=1220954593).