URI
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...
Uniform Resource Identifiers (URI) provide a simple and extensible
means for identifying a resource. This specification of URI syntax
...
... Uniform Resource Identifiers (URI) provide a simple and extensible
means for identifying a resource. This specification of URI syntax
and semantics is derived from concepts introduced by the World Wide
Web ...
... Universal Resource Identifiers in WWW"
[RFC1630]. The specification of URI is designed to meet the
recommendations laid out in "Functional Recommendations for Internet
...
... RFC1808] in order
to define a single, generic syntax for all URI. It excludes those
portions of RFC 1738(-> 4266prop | 4248prop) that defined the specific syntax of individual
...
... URL schemes; those portions will be updated as separate documents, as
will the process for registration of new URI schemes. This document
does not discuss the issues and recommendation for dealing with
characters outside of the US-ASCII ...
... Overview of URI ...
...
URI are characterized by the following definitions:
...
... identifier is an object that can act as a reference to
something that has identity. In the case of URI, the object is
a sequence of characters with a restricted syntax. ...
...
A URI can be further classified as a locator, a name, or both. The
term "Uniform Resource Locator ...
... term "Uniform Resource Locator" (URL) refers to the subset of URI
that identify resources via a representation of their primary access
mechanism (e.g., their network ...
... The term "Uniform Resource Name" (URN) refers to the subset of URI
that are required to remain globally unique and persistent even when
the resource ceases to exist or becomes unavailable ...
... The URI scheme (Section 3.1) defines the namespace of the URI, and
thus may further restrict the syntax and semantics of identifiers ...
... using that scheme. This specification defines those elements of the
URI syntax that are either required of all URI schemes or are common
to many URI schemes ...
... elements of the
URI syntax that are either required of all URI schemes or are common
to many URI schemes. It thus defines the syntax and semantics ...
... URI syntax that are either required of all URI schemes or are common
to many URI schemes. It thus defines the syntax and semantics that
are needed to implement a scheme-independent parsing mechanism for
...
... syntax and semantics that
are needed to implement a scheme-independent parsing mechanism for
URI references, such that the scheme-dependent handling of a URI can
be postponed until the scheme-dependent semantics ...
... are needed to implement a scheme-independent parsing mechanism for
URI references, such that the scheme-dependent handling of a URI can
be postponed until the scheme-dependent semantics are needed. We use
...
... they allow the most varied use of the syntax and often have a
hierarchical namespace. A parser of the URI syntax is capable of
parsing both URL and URN ...
... parsing both URL and URN references as a generic URI; once the scheme
is determined, the scheme-specific parsing can be performed on the
generic URI ...
... URI; once the scheme
is determined, the scheme-specific parsing can be performed on the
generic URI components. In other words, the URI syntax is a superset
of the syntax of all URI schemes ...
... is determined, the scheme-specific parsing can be performed on the
generic URI components. In other words, the URI syntax is a superset
of the syntax of all URI schemes.
...
... URI components. In other words, the URI syntax is a superset
of the syntax of all URI schemes.
...
... Example URI ...
...
The following examples illustrate URI that are in common use.
...
... Hierarchical URI and Relative Forms ...
...
Some URI schemes support a hierarchical naming system, where the
hierarchy of the name is denoted by a "/" delimiter separating the
components in the scheme. This document defines a scheme-independent
...
... hierarchy of the name is denoted by a "/" delimiter separating the
components in the scheme. This document defines a scheme-independent
`relative' form of URI reference that can be used in conjunction with
a `base' URI ...
... URI reference that can be used in conjunction with
a `base' URI (of a hierarchical scheme) to produce another URI. The
syntax of hierarchical URI ...
... conjunction with
a `base' URI (of a hierarchical scheme) to produce another URI. The
syntax of hierarchical URI is described in Section 3; the relative
...
... URI (of a hierarchical scheme) to produce another URI. The
syntax of hierarchical URI is described in Section 3; the relative
URI calculation is described in Section 5.
...
... syntax of hierarchical URI is described in Section 3; the relative
URI calculation is described in Section 5.
...
... URI Transcribability ...
...
The URI syntax was designed with global transcribability as one of
its main concerns. A URI is a sequence of characters from a very
...
... The URI syntax was designed with global transcribability as one of
its main concerns. A URI is a sequence of characters from a very
limited set, i.e. the letters of the basic Latin alphabet, digits,
and a few special characters. A URI ...
... URI is a sequence of characters from a very
limited set, i.e. the letters of the basic Latin alphabet, digits,
and a few special characters. A URI may be represented in a variety
of ways: e.g., ink on paper, pixels on a screen, or a sequence of
octets in a coded character set ...
... of ways: e.g., ink on paper, pixels on a screen, or a sequence of
octets in a coded character set. The interpretation of a URI depends
only on the characters used and not how those characters are
represented in a network protocol ...
... Imagine two colleagues, Sam and Kim, sitting in a pub at an
international conference and exchanging research ideas. Sam asks Kim
for a location to get more information, so Kim writes the URI for the
research site on a napkin. Upon returning home, Sam takes out the
napkin and types the URI ...
... URI for the
research site on a napkin. Upon returning home, Sam takes out the
napkin and types the URI into a computer, which then retrieves the
information to which Kim referred.
...
... A URI is a sequence of characters, which is not always
represented as a sequence of octets. ...
... A URI may be transcribed from a non-network source, and thus
should consist of characters that are most likely to be able to
...
... A URI often needs to be remembered by people, and it is easier
for people to remember a URI when it consists of meaningful
...
... A URI often needs to be remembered by people, and it is easier
for people to remember a URI when it consists of meaningful
components. ...
...
These design concerns are not always in alignment. For example, it
is often the case that the most meaningful name for a URI component
would require characters that cannot be typed into some systems. The
ability to transcribe the resource identifier ...
... ability to transcribe the resource identifier from one medium to
another was considered more important than having its URI consist of
the most meaningful of components. In local and regional contexts
...
...
This document uses two conventions to describe and define the syntax
for URI. The first, called the layout form, is a general description
of the order of components and component separators, as in
...
... The second convention is a BNF-like grammar, used to define the
formal URI syntax. The grammar is that of [RFC822], except that "|"
is used to designate alternatives. Briefly, rules are separated from
...
... Unlike many specifications that use a BNF-like grammar to define the
bytes (octets) allowed by a protocol, the URI grammar is defined in
terms of characters. Each literal in the grammar corresponds to the
...
... encoding of that
character in any particular coded character set. How a URI is
represented in terms of bits and bytes on the wire is dependent upon
...
...
The complete URI syntax is collected in Appendix A.
...
... URI Characters and Escape Sequences ...
...
URI consist of a restricted set of characters, primarily chosen to
aid transcribability and usability both in computer systems and in
non-computer communications. Characters used conventionally as
...
... aid transcribability and usability both in computer systems and in
non-computer communications. Characters used conventionally as
delimiters around URI were excluded. The restricted set of
characters consists of digits, letters, and a few graphic symbols
were chosen from those common to most of the character encodings ...
...
Within a URI, characters are either used as delimiters, or to
represent strings of data (octets) within the delimited portions.
Octets are either represented directly by a character (using the US-
...
...
The relationship between URI and characters has been a source of
confusion for characters that are not part of US-ASCII. To describe
...
... entity) and an "octet" (an 8-bit
byte). There are two mappings, one from URI characters to octets, and
a second from octets to original characters:
...
...
A URI is represented as a sequence of characters, not as a sequence
of octets. That is because URI might be "transported" by means that
...
... A URI is represented as a sequence of characters, not as a sequence
of octets. That is because URI might be "transported" by means that
are not through a computer network, e.g., printed on paper, read over
...
...
A URI scheme may define a mapping from URI characters to octets;
whether this is done depends on the scheme. Commonly, within a
...
...
A URI scheme may define a mapping from URI characters to octets;
whether this is done depends on the scheme. Commonly, within a
delimited component of a URI ...
... URI characters to octets;
whether this is done depends on the scheme. Commonly, within a
delimited component of a URI, a sequence of characters may be used to
represent a sequence of octets. For example, the character "a"
represents the octet 97 (decimal), while the character sequence ...
...
There is a second translation for some resources: the sequence of
octets defined by a component of the URI is subsequently used to
represent a sequence of characters. A 'charset' defines this mapping.
...
... there might be more than one [RFC2277]. However, there is currently
no provision within the generic URI syntax to accomplish this
identification. An individual URI scheme may require a single
...
... no provision within the generic URI syntax to accomplish this
identification. An individual URI scheme may require a single
charset, define a default charset ...
... It is expected that a systematic treatment of character encoding
within URI will be developed as a future modification of this
specification.
...
...
Many URI include components consisting of or delimited by, certain
special characters. These characters are called "reserved", since
their usage within the URI ...
... URI include components consisting of or delimited by, certain
special characters. These characters are called "reserved", since
their usage within the URI component is limited to their reserved
purpose. If the data for a URI component would conflict with the
...
... their usage within the URI component is limited to their reserved
purpose. If the data for a URI component would conflict with the
reserved purpose, then the conflicting data must be escaped before
forming the URI ...
... URI component would conflict with the
reserved purpose, then the conflicting data must be escaped before
forming the URI.
...
... The "reserved" syntax class above refers to those characters that are
allowed within a URI, but which may not be allowed within a
particular component of the generic URI syntax; they are used as
...
... allowed within a URI, but which may not be allowed within a
particular component of the generic URI syntax; they are used as
delimiters of the components described in Section 3.
...
... Characters in the "reserved" set are not reserved in all contexts.
The set of characters actually reserved within any given URI
component is defined by that component. In general, a character is
reserved if the semantics ...
... component is defined by that component. In general, a character is
reserved if the semantics of the URI changes if the character is
replaced with its escaped US-ASCII encoding ...
...
Data characters that are allowed in a URI but do not have a reserved
purpose are called unreserved. These include upper and lower case
letters, decimal digits, and a limited set of punctuation marks and
...
... Unreserved characters can be escaped without changing the semantics
of the URI, but this should not be done unless the URI is being used
in a context ...
... semantics
of the URI, but this should not be done unless the URI is being used
in a context that does not allow the unescaped character to appear.
...
...
A URI is always in an "escaped" form, since escaping or unescaping a
completed URI might change its semantics ...
... A URI is always in an "escaped" form, since escaping or unescaping a
completed URI might change its semantics. Normally, the only time
escape encodings ...
... semantics. Normally, the only time
escape encodings can safely be made is when the URI is being created
from its component parts; each component may have its own set of
...
... generating or interpreting that component can determine whether or
not escaping a character will change its semantics. Likewise, a URI
must be separated into its components before the escaped characters
within those components can be safely decoded.
...
... unreserved
character may appear escaped; for example, some of the unreserved
"mark" characters are automatically escaped by some systems. If the
given URI scheme defines a canonicalization algorithm, then
...
... Because the percent "%" character always has the reserved purpose of
being the escape indicator, it must be escaped as "%25" in order to
be used as data within a URI. Implementers should be careful not to
escape or unescape the same string more than once, since unescaping
...
...
Although they are disallowed within the URI syntax, we include here a
description of those US-ASCII characters that have been excluded and
...
... US-ASCII coded character set are not
used within a URI, both because they are non-printable and because
they are likely to be misinterpreted by some control mechanisms.
...
... The space character is excluded because significant spaces may
disappear and insignificant spaces may be introduced when URI are
transcribed or typeset or subjected to the treatment of word-
processing programs. Whitespace is also used to delimit URI ...
... URI are
transcribed or typeset or subjected to the treatment of word-
processing programs. Whitespace is also used to delimit URI in many
contexts.
...
...
The angle-bracket "<" and ">" and double-quote (") characters are
excluded because they are often used as the delimiters around URI in
text documents and protocol fields. The character "#" is excluded
...
... text documents and protocol fields. The character "#" is excluded
because it is used to delimit a URI from a fragment identifier in URI
references (Section 4). The percent character "%" is excluded because
...
... because it is used to delimit a URI from a fragment identifier in URI
references (Section 4). The percent character "%" is excluded because
it is used for the encoding of escaped characters.
...
...
Data corresponding to excluded characters must be escaped in order to
be properly represented within a URI.
...
... URI Syntactic Components ...
...
The URI syntax is dependent upon the scheme. In general, absolute
URI are written as follows:
...
...
The URI syntax is dependent upon the scheme. In general, absolute
URI are written as follows:
...
...
An absolute URI contains the name of the scheme being used (<scheme>)
followed by a colon (":") and then a string (the <scheme-specific-part> ...
...
The URI syntax does not require that the scheme-specific-part have
any general structure or set of semantics which is common among all
...
... any general structure or set of semantics which is common among all
URI. However, a subset of URI do share a common syntax for
representing hierarchical relationships within the namespace ...
... semantics which is common among all
URI. However, a subset of URI do share a common syntax for
representing hierarchical relationships within the namespace. This
...
... representing hierarchical relationships within the namespace. This
"generic URI" syntax consists of a sequence of four main components:
...
...
each of which, except <scheme>, may be absent from a particular URI.
For example, some URI schemes do not allow an <authority> ...
... <scheme>, may be absent from a particular URI.
For example, some URI schemes do not allow an <authority> component,
and others do not use a <query> ...
...
URI that are hierarchical in nature use the slash "/" character for
separating hierarchical components. For some file systems, a "/"
...
... separating hierarchical components. For some file systems, a "/"
character (used to denote the hierarchical structure of a URI) is the
delimiter used to construct a file name hierarchy, and thus the URI
...
... character (used to denote the hierarchical structure of a URI) is the
delimiter used to construct a file name hierarchy, and thus the URI
path will look similar to a file pathname. This does NOT imply that
the resource is a file or that the URI ...
... URI
path will look similar to a file pathname. This does NOT imply that
the resource is a file or that the URI maps to an actual filesystem
pathname.
...
...
URI that do not make use of the slash "/" character for separating
hierarchical components are considered opaque by the generic URI ...
... URI that do not make use of the slash "/" character for separating
hierarchical components are considered opaque by the generic URI
parser.
...
... <opaque_part> constructs, since they are mutually exclusive for any
given URI and can be parsed as a single component.
...
... methods of access to resources,
there are a variety of schemes for identifying such resources. The
URI syntax consists of a sequence of components separated by reserved
characters, with the first component defining the semantics for the
...
... reserved
characters, with the first component defining the semantics for the
remainder of the URI string.
...
... lower case letter and followed by any combination of lower case
letters, digits, plus ("+"), period ("."), or hyphen ("-"). For
resiliency, programs interpreting URI should treat upper case letters
as equivalent to lower case in scheme names (e.g., allow "HTTP" as
...
...
Relative URI references are distinguished from absolute URI in that
they do not begin with a scheme name. Instead, the scheme is
...
...
Relative URI references are distinguished from absolute URI in that
they do not begin with a scheme name. Instead, the scheme is
inherited from the base URI ...
... absolute URI in that
they do not begin with a scheme name. Instead, the scheme is
inherited from the base URI, as described in Section 5.2.
...
...
Many URI schemes include a top hierarchical element for a naming
authority, such that the namespace ...
... naming
authority, such that the namespace defined by the remainder of the
URI is governed by that authority. This authority component is
...
... authority component is preceded by a double slash "//" and is
terminated by the next slash "/", question-mark "?", or by the end of
the URI. Within the authority component, the characters ";", ":",
"@", "?", and "/" are reserved.
...
...
An authority component is not required for a URI scheme to make use
of relative references. A base URI without an authority component ...
... authority component is not required for a URI scheme to make use
of relative references. A base URI without an authority component
implies that any relative reference ...
... registry-based naming authority is specific to the
URI scheme, but constrained to the allowed characters for an
authority component.
...
... specified server on the Internet use a common syntax for the server
component of the URI's scheme-specific data:
...
... field. This practice is NOT RECOMMENDED, because the passing of
authentication information in clear text (such as URI) has proven to
be a security risk in almost every case where it has been used.
...
... URI References ...
...
The term "URI-reference" is used here to denote the common usage of a
resource identifier. A URI reference ...
... URI-reference" is used here to denote the common usage of a
resource identifier. A URI reference may be absolute or relative,
and may have additional information attached in the form of a
fragment identifier ...
... and may have additional information attached in the form of a
fragment identifier. However, "the URI" that results from such a
reference includes only the absolute URI after the fragment
identifier ...
... fragment identifier. However, "the URI" that results from such a
reference includes only the absolute URI after the fragment
identifier (if any) is removed and after any relative URI ...
... absolute URI after the fragment
identifier (if any) is removed and after any relative URI is resolved
to its absolute form. Although it is possible to limit the
discussion ...
... to its absolute form. Although it is possible to limit the
discussion of URI syntax and semantics to that of the absolute
result, most usage of URI ...
... URI syntax and semantics to that of the absolute
result, most usage of URI is within general URI references, and it is
impossible to obtain the URI ...
... semantics to that of the absolute
result, most usage of URI is within general URI references, and it is
impossible to obtain the URI from such a reference without also
...
... URI is within general URI references, and it is
impossible to obtain the URI from such a reference without also
parsing the fragment and resolving the relative form.
...
...
The syntax for relative URI is a shortened form of that for absolute
URI, where some prefix of the URI ...
...
The syntax for relative URI is a shortened form of that for absolute
URI, where some prefix of the URI is missing and certain path
...
... URI is a shortened form of that for absolute
URI, where some prefix of the URI is missing and certain path
components ("." and "..") have a special meaning when, and only when,
interpreting a relative path. The relative URI syntax ...
... URI is missing and certain path
components ("." and "..") have a special meaning when, and only when,
interpreting a relative path. The relative URI syntax is defined in
Section 5.
...
...
When a URI reference is used to perform a retrieval action on the
identified resource, the optional fragment identifier, separated from
...
... identified resource, the optional fragment identifier, separated from
the URI by a crosshatch ("#") character, consists of additional
reference information to be interpreted by the user agent ...
... agent after the
retrieval action has been successfully completed. As such, it is not
part of a URI, but is often used in conjunction with a URI.
...
... semantics of a fragment identifier is a property of the data
resulting from a retrieval action, regardless of the type of URI used
in the reference. Therefore, the format and interpretation of
fragment identifiers ...
... RFC2046] of the
retrieval result. The character restrictions described in Section 2
for URI also apply to the fragment in a URI-reference. Individual
...
... for URI also apply to the fragment in a URI-reference. Individual
media types may define additional restrictions or structure within
...
...
A fragment identifier is only meaningful when a URI reference is
intended for retrieval and the result of that retrieval is a document
for which the identified fragment ...
...
A URI reference that does not contain a URI is a reference to the
current document. In other words, an empty URI reference ...
...
A URI reference that does not contain a URI is a reference to the
current document. In other words, an empty URI reference within a
...
... URI reference that does not contain a URI is a reference to the
current document. In other words, an empty URI reference within a
document is interpreted as a reference to the start of that document,
...
... fragment of that document. Traversal of such a
reference should not result in an additional retrieval action.
However, if the URI reference occurs in a context that is always
intended to result in a new request, as in the case of HTML ...
... HTML's FORM
element, then an empty URI reference represents the base URI of the
current document and should be replaced by that URI ...
... element, then an empty URI reference represents the base URI of the
current document and should be replaced by that URI when transformed
...
... URI reference represents the base URI of the
current document and should be replaced by that URI when transformed
into a request.
...
... Parsing a URI Reference ...
...
A URI reference is typically parsed according to the four main
components and fragment identifier in order to determine what
...
... greedy algorithm is used for disambiguation: the left-most matching
rule soaks up as much of the URI reference string as it is capable of
matching. In other words, the authority component wins.
...
... Relative URI References ...
... group or "tree" of documents has been
constructed to serve a common purpose; the vast majority of URI in
these documents point to resources within the tree rather than
...
...
Relative addressing of URI allows document trees to be partially
independent of their location and access scheme. For instance, it is
...
... possible for a single set of hypertext documents to be simultaneously
accessible and traversable via each of the "file", "http", and "ftp"
schemes if the documents refer to each other using relative URI.
Furthermore, such document trees can be moved, as a whole, without
...
... changing any of the relative references. Experience within the WWW
has demonstrated that the ability to perform relative referencing is
necessary for the long-term usability of embedded URI.
...
... <absoluteURI> (Section 3) in order to express a reference that is
relative to the namespace of another hierarchical URI.
...
... path segment which contains a colon
character cannot be used as the first segment of a relative URI path
(e.g., "this:that"), because it would be mistaken for a scheme name.
...
...
It is not necessary for all URI within a given scheme to be
restricted to the <hier_part> syntax, since the hierarchical
...
... restricted to the <hier_part> syntax, since the hierarchical
properties of that syntax are only necessary when relative URI are
used within a particular document. Documents can only make use of
relative URI ...
... URI are
used within a particular document. Documents can only make use of
relative URI when their base URI fits within the <hier_part> syntax.
...
... used within a particular document. Documents can only make use of
relative URI when their base URI fits within the <hier_part> syntax.
It is assumed that any document which contains a relative reference ...
... It is assumed that any document which contains a relative reference
will also have a base URI that obeys the syntax. In other words,
relative URI cannot be used within a document that has an unsuitable
...
... will also have a base URI that obeys the syntax. In other words,
relative URI cannot be used within a document that has an unsuitable
base URI.
...
...
Some URI schemes do not allow a hierarchical syntax matching the
<hier_part> syntax, and thus cannot use relative references.
...
... Establishing a Base URI ...
...
The term "relative URI" implies that there exists some absolute "base
URI" against which the relative reference is applied. Indeed, the
...
...
The term "relative URI" implies that there exists some absolute "base
URI" against which the relative reference is applied. Indeed, the
base URI ...
... base
URI" against which the relative reference is applied. Indeed, the
base URI is necessary to define the semantics of any relative URI
reference; without it, a relative reference ...
... base URI is necessary to define the semantics of any relative URI
reference; without it, a relative reference is meaningless. In order
for relative URI ...
... URI
reference; without it, a relative reference is meaningless. In order
for relative URI to be usable within a document, the base URI of that
document must be known to the parser.
...
... relative reference is meaningless. In order
for relative URI to be usable within a document, the base URI of that
document must be known to the parser.
...
...
The base URI of a document can be established in one of four ways,
listed below in order of precedence. The order of precedence can be
thought of in terms of layers, where the innermost defined base URI ...
... base URI of a document can be established in one of four ways,
listed below in order of precedence. The order of precedence can be
thought of in terms of layers, where the innermost defined base URI
has the highest precedence. This can be visualized graphically as:
...
... | | | | | <relative_reference> | | | | |
| | | | `----------------------------------' | | | |
| | | | (5.1.1) Base URI embedded in the | | | |
| | | | document's content | | | |
| | | `----------------------------------------' | | |
...
... | | | | document's content | | | |
| | | `----------------------------------------' | | |
| | | (5.1.2) Base URI of the encapsulating entity | | |
| | | (message, document, or none). | | |
...
... | | | (message, document, or none). | | |
| | `----------------------------------------------' | |
| | (5.1.3) URI used to retrieve the entity | |
| `----------------------------------------------------' |
...
... entity | |
| `----------------------------------------------------' |
| (5.1.4) Default Base URI is application-dependent |
`----------------------------------------------------------'
...
... Base URI within Document Content ...
...
Within certain document media types, the base URI of the document can
be embedded within the content itself such that it can be readily
obtained by a parser. This can be useful for descriptive documents,
...
... It is beyond the scope of this document to specify how, for each
media type, the base URI can be embedded. It is assumed that user
agents manipulating such media types will be able to obtain the
...
... appropriate syntax from that media type's specification. An example
of how the base URI can be embedded in the Hypertext Markup Language
(HTML ...
...
A mechanism for embedding the base URI within MIME container types
(e.g., the message and multipart types) is defined by MHTML
...
... header syntax,
but which do allow some form of tagged metainformation to be included
within messages, may define their own syntax for defining the base
URI as part of a message.
...
... Base URI from the Encapsulating Entity ...
...
If no base URI is embedded, the base URI of a document is defined by
the document's retrieval context ...
...
If no base URI is embedded, the base URI of a document is defined by
the document's retrieval context. For a document that is enclosed
...
... retrieval context is that entity; thus, the default base URI of the
document is the base URI of the entity ...
... entity; thus, the default base URI of the
document is the base URI of the entity in which the document is
encapsulated ...
... composite entity),
then, if a URI was used to retrieve the base document, that URI shall
be considered the base URI ...
... entity),
then, if a URI was used to retrieve the base document, that URI shall
be considered the base URI. Note that if the retrieval was the
...
... URI was used to retrieve the base document, that URI shall
be considered the base URI. Note that if the retrieval was the
result of a redirected request, the last URI used (i.e., that which
...
... be considered the base URI. Note that if the retrieval was the
result of a redirected request, the last URI used (i.e., that which
resulted in the actual retrieval of the document) is the base URI.
...
... result of a redirected request, the last URI used (i.e., that which
resulted in the actual retrieval of the document) is the base URI.
...
... Default Base URI ...
...
If none of the conditions described in Sections 5.1.1--5.1.3 apply,
then the base URI is defined by the context of the application.
Since this definition is necessarily application-dependent, failing
...
... context of the application.
Since this definition is necessarily application-dependent, failing
to define the base URI using one of the other methods may result in
the same content being interpreted differently by different types of
...
...
It is the responsibility of the distributor(s) of a document
containing relative URI to ensure that the base URI for that document
can be established. It must be emphasized that relative URI ...
... It is the responsibility of the distributor(s) of a document
containing relative URI to ensure that the base URI for that document
can be established. It must be emphasized that relative URI cannot
...
... URI to ensure that the base URI for that document
can be established. It must be emphasized that relative URI cannot
be used reliably in situations where the document's base URI is not
...
... can be established. It must be emphasized that relative URI cannot
be used reliably in situations where the document's base URI is not
well-defined.
...
...
This section describes an example algorithm for resolving URI
references that might be relative to a given base URI.
...
... This section describes an example algorithm for resolving URI
references that might be relative to a given base URI.
...
...
The base URI is established according to the rules of Section 5.1 and
parsed into the four main components as described in Section 3. Note
that only the scheme component is required to be present in the base
URI ...
... base URI is established according to the rules of Section 5.1 and
parsed into the four main components as described in Section 3. Note
that only the scheme component is required to be present in the base
URI; the other components may be empty or undefined. A component is
undefined if its preceding separator does not appear in the URI
reference; the path component is never undefined, though it may be
...
... that only the scheme component is required to be present in the base
URI; the other components may be empty or undefined. A component is
undefined if its preceding separator does not appear in the URI
reference; the path component is never undefined, though it may be
empty. The base URI's query ...
... undefined if its preceding separator does not appear in the URI
reference; the path component is never undefined, though it may be
empty. The base URI's query component is not used by the resolution
algorithm ...
...
For each URI reference, the following steps are performed in order:
...
... The URI reference is parsed into the potential four components and
fragment identifier, as described in Section 4.3. ...
... query components are undefined, then it is a reference to the
current document and we are done. Otherwise, the reference URI's
query and fragment ...
... query and fragment components are defined as found (or not found)
within the URI reference and not inherited from the base URI. ...
... fragment components are defined as found (or not found)
within the URI reference and not inherited from the base URI. ...
... starts with a scheme name, then the reference is interpreted as an
absolute URI and we are done. Otherwise, the reference URI's
scheme is inherited from the base URI ...
... starts with a scheme name, then the reference is interpreted as an
absolute URI and we are done. Otherwise, the reference URI's
scheme is inherited from the base URI's scheme component. ...
... absolute URI and we are done. Otherwise, the reference URI's
scheme is inherited from the base URI's scheme component. ...
... Due to a loophole in prior specifications [RFC1630], some parsers
allow the scheme name to be present in a relative URI if it is the
same as the base URI scheme. Unfortunately, this can conflict
...
... allow the scheme name to be present in a relative URI if it is the
same as the base URI scheme. Unfortunately, this can conflict
with the correct parsing of non-hierarchical URI. For backwards
compatibility ...
... same as the base URI scheme. Unfortunately, this can conflict
with the correct parsing of non-hierarchical URI. For backwards
compatibility, an implementation may work around such references
by removing ...
... backwards
compatibility, an implementation may work around such references
by removing the scheme if it matches that of the base URI and the
scheme is known to always use the <hier_part> syntax. The parser
...
... network-path and we skip to step 7. Otherwise, the reference
URI's authority is inherited from the base URI's authority
component ...
... URI's authority is inherited from the base URI's authority
component, which will also be undefined if the URI scheme does not
...
... authority is inherited from the base URI's authority
component, which will also be undefined if the URI scheme does not
use an authority component. ...
... If this step is reached, then we are resolving a relative-path
reference. The relative path needs to be merged with the base
URI's path. Although there are many ways to do this, we will
describe a simple method using a separate string buffer ...
... All but the last segment of the base URI's path component is
copied to the buffer. In other words, any characters after the
...
... considered to be in error. Implementations may handle this
error by retaining these components in the resolved path (i.e.,
treating them as part of the final URI), by removing them from
the resolved path (i.e., discarding relative levels above the
...
...
The resulting URI components, including any inherited from the
base URI, are recombined to give the absolute form of the URI
reference ...
... The resulting URI components, including any inherited from the
base URI, are recombined to give the absolute form of the URI
reference. Using pseudocode, this would be
...
... URI components, including any inherited from the
base URI, are recombined to give the absolute form of the URI
reference. Using pseudocode, this would be
...
... URI Normalization and Equivalence ...
...
In many cases, different URI strings may actually identify the
identical resource. For example, the host names used in URL ...
...
A URI does not in itself pose a security threat. Users should beware
that there is no general guarantee that a URL ...
... obtained from the person(s) controlling that namespace and the
resource in question. A specific URI scheme may include additional
semantics, such as name persistence, if those semantics ...
... B. Parsing a URI Reference with a Regular Expression ...
...
As described in Section 4.3, the generic URI syntax is not sufficient
to disambiguate the components of some forms of URI. Since the
...
... As described in Section 4.3, the generic URI syntax is not sufficient
to disambiguate the components of some forms of URI. Since the
"greedy algorithm" described in that section is identical to the
...
... regular expression for parsing the
potential four components and fragment identifier of a URI reference.
...
...
The following line is the regular expression for breaking-down a URI
reference into its components.
...
...
and, going in the opposite direction, we can recreate a URI reference
from its components using the algorithm in step 7 of Section 5.2.
...
... C. Examples of Resolving Relative URI References ...
...
Within an object with a well-defined base URI of
...
...
the relative URI would be resolved as follows:
...
... Although the following abnormal examples are unlikely to occur in
normal practice, all URI parsers should be capable of resolving them
consistently. Each example uses the same base as above.
...
... relative path ".." segments than there are hierarchical levels in the
base URI's path. Note that the ".." syntax cannot be used to change
the authority component of a URI ...
... base URI's path. Note that the ".." syntax cannot be used to change
the authority component of a URI.
...
... In practice, some implementations strip leading relative symbolic
elements (".", "..") after applying a relative URI calculation, based
on the theory that compensating for obvious author errors is better
than allowing the request to fail. Thus, the above two references
...
...
Less likely are cases where the relative URI uses unnecessary or
nonsensical forms of the "." and ".." complete path segments.
...
... client applications remove the query component from the base URI
before resolving relative URI. However, some applications fail to
...
... query component from the base URI
before resolving relative URI. However, some applications fail to
separate the reference's query and/or fragment ...
...
Some parsers allow the scheme name to be present in a relative URI if
it is the same as the base URI scheme. This is considered to be a
...
... Some parsers allow the scheme name to be present in a relative URI if
it is the same as the base URI scheme. This is considered to be a
loophole in prior specifications of partial URI [RFC1630 ...
... it is the same as the base URI scheme. This is considered to be a
loophole in prior specifications of partial URI [RFC1630]. Its use
should be avoided.
...
... D. Embedding the Base URI in HTML documents ...
...
It is useful to consider an example of how the base URI of a document
can be embedded within the document's content. In this appendix, we
describe how documents written in the Hypertext Markup Language ...
... (HTML) [RFC1866] can include an embedded base URI. This appendix
does not form a part of the URI specification and should not be
...
... RFC1866] can include an embedded base URI. This appendix
does not form a part of the URI specification and should not be
considered as anything more than a descriptive example.
...
... "HEAD" portion of a document, signals that the parser should use the
BASE element's "HREF" attribute as the base URI for resolving any
relative URI. The "HREF" attribute must be an absolute URI ...
... element's "HREF" attribute as the base URI for resolving any
relative URI. The "HREF" attribute must be an absolute URI. Note
that, in HTML ...
... base URI for resolving any
relative URI. The "HREF" attribute must be an absolute URI. Note
that, in HTML, element ...
...
A parser reading the example document should interpret the given
relative URI "../x" as representing the absolute URI
...
... A parser reading the example document should interpret the given
relative URI "../x" as representing the absolute URI
...
...
URI are often transmitted through formats that do not provide a clear
context for their interpretation. For example, there are many
...
... context for their interpretation. For example, there are many
occasions when URI are included in plain text; examples include text
sent in electronic mail, USENET ...
... USENET news messages, and, most importantly,
printed on paper. In such cases, it is important to be able to
delimit the URI from the rest of the text, and in particular from
punctuation marks that might be mistaken for part of the URI.
...
... delimit the URI from the rest of the text, and in particular from
punctuation marks that might be mistaken for part of the URI.
...
...
In practice, URI are delimited in a variety of ways, but usually
within double-quotes "http://test.com/", angle brackets
<http://test.com/>, or just using whitespace http://test.com/ ...
...
In the case where a fragment identifier is associated with a URI
reference, the fragment would be placed within the brackets as well
(separated from the URI ...
... URI
reference, the fragment would be placed within the brackets as well
(separated from the URI with a "#" character).
...
...
In some cases, extra whitespace (spaces, linebreaks, tabs, etc.) may
need to be added to break long URI across lines. The whitespace
should be ignored when extracting the URI.
...
... need to be added to break long URI across lines. The whitespace
should be ignored when extracting the URI.
...
... Because some typesetters and printers may (erroneously) introduce a
hyphen at the end of line when breaking a line, the interpreter of a
URI containing a line break immediately after a hyphen should ignore
all unescaped whitespace around the line break ...
... all unescaped whitespace around the line break, and should be aware
that the hyphen may or may not actually be part of the URI.
...
...
Using <> angle brackets around each URI is especially recommended as
a delimiting style for URI that contain whitespace.
...
... Using <> angle brackets around each URI is especially recommended as
a delimiting style for URI that contain whitespace.
...
...
For robustness, software that accepts user-typed URI should attempt
to recognize and strip both delimiters and embedded whitespace.
...
...
contains the URI references
...
...
Section 4 (URI References) was added to stem the confusion regarding
"what is a URI" and how to describe fragment identifiers ...
... Section 4 (URI References) was added to stem the confusion regarding
"what is a URI" and how to describe fragment identifiers given that
they are not part of the URI ...
... URI" and how to describe fragment identifiers given that
they are not part of the URI, but are part of the URI syntax and
parsing concerns. In addition, it provides a reference definition
...
... fragment identifiers given that
they are not part of the URI, but are part of the URI syntax and
parsing concerns. In addition, it provides a reference definition
for use by other IETF ...
... HTML, HTTP, etc.) that have
previously attempted to redefine the URI syntax in order to account
for the presence of fragment identifiers in URI references ...
...
Section 2.4 was rewritten to clarify a number of misinterpretations
and to leave room for fully internationalized URI.
...
...
Changed to URI syntax instead of just URL.
...
...
Confusion regarding the terms "character encoding", the URI
"character set", and the escaping of characters with %<hex> ...
... just US-ASCII octets. Unless otherwise noted here, these
modifications do not affect the URI syntax.
...
... 1738(-> 4266prop | 4248prop) and RFC 1808(-> 3986std66) refer to the "reserved" set of characters
as if URI-interpreting software were limited to a single set of
characters with a reserved purpose (i.e., as meaning something other
than the data to which the characters correspond), and that this set
...
... characters with a reserved purpose (i.e., as meaning something other
than the data to which the characters correspond), and that this set
was fixed by the URI scheme. However, this has not been true in
practice; any character that is interpreted differently when it is
escaped is, in effect, reserved. Furthermore, the interpreting
...
... engine on a HTTP server is often dependent on the resource, not just
the URI scheme. The description of reserved characters has been
changed accordingly.
...
...
The syntax for URI scheme has been changed to require that all
schemes begin with an alpha character.
...
... showed that many applications treat it as reserved for separating the
query component from the rest of the URI.
...
... 1738(-> 4266prop | 4248prop) specified that the path was separated from the authority
portion of a URI by a slash. RFC 1808(-> 3986std66) followed suit, but with a
fudge of carrying around the separator as a "prefix ...
... since it considered the slash to be part of the path. In writing
this specification, it was found to be impossible to accurately
describe and retain the difference between the two URI
...
...
The recommendations for delimiting URI in context (Appendix E) have
been adjusted to reflect current practice.
...
... RFC 1808(-> 3986std66) described various schemes as either having or not having the
properties of the generic URI syntax. However, the only requirement
is that the particular document containing the relative references
...
... requirement
is that the particular document containing the relative references
have a base URI that abides by the generic URI syntax, regardless of
the URI scheme ...
... is that the particular document containing the relative references
have a base URI that abides by the generic URI syntax, regardless of
the URI scheme, so the associated description has been updated to
...
... base URI that abides by the generic URI syntax, regardless of
the URI scheme, so the associated description has been updated to
reflect that.
...
... has been removed from the algorithm for resolving a relative URI
reference. The resolution examples in Appendix C have been modified
to reflect this change.
...
...
Implementations are now allowed to work around misformed relative
references that are prefixed by the same scheme as the base URI, but
only for schemes known to use the <hier_part> syntax.
...