Asahina Antenna Metadata Format (HINA) 2.2, rev. 0.11

May 9, 2001

Overview

This document describes Hina-Di, the metadata format used by Asahina Antenna. In this document, “metadata” is defined as data on a webpage such as its last update time or its author. Asahina Antenna acts as a feed reader for Hina-Di.

Conventions used in this document

This document uses the Backus-Naur notation (RFC 822) to formally specify the format.

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in BCP 14 (RFC 2119, RFC 8174) when, and only when, they appear in all capitals, as shown here.

Data Types

The basic data types that constitute Hina-Di are listed below. The US-ASCII character set is defined by ANSI X3.4-1986.

OCTET     = <any 8-bit sequence of data>
CHAR      = <any US-ASCII character (octets 0 - 127)>
UPALPHA   = <any US-ASCII uppercase letter "A".."Z">
LOALPHA   = <any US-ASCII lowercase letter "a".."z">
ALPHA     = UPALPHA | LOALPHA
DIGIT     = <any US-ASCII digit "0".."9">
WORD      = 1*(ALPHA|DIGIT)

CTL       = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
CR        = <US-ASCII CR, carriage return (13)>
LF        = <US-ASCII LF, linefeed (10)>
SP        = <US-ASCII SP, space (32)>
HT        = <US-ASCII HT, horizontal-tab (9)>
<">       = <US-ASCII double-quote mark (34)>

CRLF      = CR LF

TEXT      = <any OCTET except CTLs, but including HT>
TOKEN     = <any TEXT, but don't start with SP or HT>

SEPARATOR = ":" 1*(SP|HT)
DELIMITER = "," *(SP|HT)
SLASH     = "/" *(SP|HT)

Structure

A Hina-Di file consists of a series of blocks that summarize the metadata on a website: a header block, followed by one or more entity blocks.

hina-di = header-block
          1*( entity-block )

Block

A block is a set of metadata for a document. Each metadata is represented as a single header, in a manner similar to RFC 822, with a field name and a field value.

Field names in a block MUST be unique. A block with duplicate field names MUST be discarded.

Field names are case-sensitive. Field values may be case-sensitive, depending on the field.

line-format = field-name SEPARATOR field-value CRLF
field-name  = WORD *( "-" WORD)
field-value = TOKEN

Header block

Exactly one header block MUST appear in a Hina-Di file, and it MUST be the first block. It holds metadata about the Hina-Di file itself.

header-block  = HINA
                Hinadi-Header
                CRLF
Hinadi-Header = 1*( User-Agent
                    | Content-Type
                    | Date )

Entity block

One or more entity blocks MUST be present after the header block. Each entity block defines metadata about a specific document.

Entity-block = URL ( HINA-Version
                   | Virtual
                   | Content-Type
                   | Date
                   | Title
                   | Author-Name
                   | Expires
                   | Expire
                   | Last-Modified
                   | Last-Modified-Detected
                   | Server
                   | Authorized
                   | Authorized-url
                   | Method
                   | Keyword
                   | Image-Width
                   | Image-Height
                   | Experimental-field
                   | Undefined-field
                   CRLF )

Fields

This section defines the various fields that may be found in blocks. All fields are OPTIONAL and case-insensitive unless otherwise specified.

HINA

Indicates that this is a Hina-Di file, and includes its version. This field is REQUIRED as the first field of Hina-Di files.

HINA           = "HINA" "/" hinadi-version CRLF
hinadi-version = "2.2beta"

User-Agent

Name of the user agent that created this Hina-Di file. This field is REQUIRED in header blocks. The value of this field is case-sensitive.

User-Agent = "User-Agent" SEPARATOR TOKEN CRLF

URL

URL of the document, compliant with RFC 2396. This field is REQUIRED in entity blocks. Making this field the first field of an entity block is RECOMMENDED. The value of this field is case-sensitive to the extent defined by RFC 2396.

URL         = "URL" SEPARATOR rfc2396-url CRLF
rfc2396-url = <URI described in section 5.1.2 "Request-URI" in RFC 2396>

HINA-Version

Specifies that the integrity of the entity block was guaranteed according to the specification of a specific Hina-Di version. If this field is missing from an entity block, it means the block might be incomplete.

HINA-Version = "HINA-Version" SEPARATOR version
version      = "HINA" "/" 1*( DIGIT ) "." 1*( DIGIT )

Virtual

URL of another Hina-Di file that holds the entity block, compliant with RFC 2396.

If there are fields in the entity block other than Virtual, then it takes the same meaning as the regular URL field.

The value of this field is case-sensitive to the extent defined by RFC 2396.

Virtual     = "Virtual" SEPARATOR rfc2396-url CRLF
rfc2396-url = <URI described in section 5.1.2 "Request-URI" in RFC 2396>

Note that the original version of the document defines the Virtual feed as Vitural.

Content-Type

MIME type of the Hina-Di file or the document, as described in RFC 1521. The value of this field is case-sensitive to the extent defined by RFC 1521.

Content-Type = "Content-Type" SEPARATOR rfc1521-type
rfc1521-type = <Content-Type as described in RFC 1521>

Date

The date and time when the block or the Hina-Di file was generated. The dates MUST comply with RFC 1123, better described in section 3.3 of RFC 2616. The value of this field is case-sensitive.

Date         = "Date" SEPARATOR rfc1123-date CRLF
rfc1123-date = <rfc1123-date described in section 3.3 "Date/Time Formats" in RFC 2616>

Title

The title of the document.

Title = "Title" SEPARATOR TOKEN CRLF

Author-Name

Name of the author of the document. The value of this field is case-sensitive.

Author-Name = "Author-Name" SEPARATOR TOKEN CRLF

Expires

Expiration date for the block. The dates MUST comply with RFC 1123, better described in section 3.3 of RFC 2616. The value of this field is case-sensitive to the extent defined by RFC 2616.

Expires = "Expires" SEPARATOR rfc1123-date CRLF

Expire

Alias for the Expires field, included for backwards compatibility.

Expire = "Expire" SEPARATOR rfc1123-date CRLF

Last-Modified

Date and time when the document was last updated. The dates MUST comply with RFC 1123, better described in section 3.3 of RFC 2616. The value of this field is case-sensitive to the extent defined by RFC 2616.

Last-Modified = "Last-Modified" SEPARATOR rfc1123-date CRLF

Last-Modified-Detected

Date and time representing when the user agent retrieved the document’s metadata. The dates MUST comply with RFC 1123, better described in section 3.3 of RFC 2616. The value of this field is case-sensitive to the extent defined by RFC 2616.

Last-Modified-Detected = "Last-Modified-Detected" SEPARATOR rfc1123-date CRLF

Server

User agent string of the server used to retrieve the metadata of the document described by this entity block.

Server = "Server" SEPARATOR TOKEN CRLF

Authorized

The user agent that retrieved the metadata of the document described by this entity block.

Authorized = "Authorized" SEPARATOR TOKEN CRLF WORD

Authorized-url

URL of a page describing the user agent referred to in the Authorized field, compliant with RFC 2396. The value of this field is case-sensitive to the extent defined by RFC 2396.

Authorized-url = "Authorized-url" SEPARATOR rfc2396-url CRLF

Method

Describes the chain of propagation that this entity block went through.

Method      = "Method" SEPARATOR method-type *(SLASH method-type) (SLASH result-code)
method-type = "GET" | "HEAD" | "FILE" | "REMOTE"
result-code = <URI described on "???????" in RFC 2396>

Method types

GET

Metadata retrieved using a HTTP GET request.

HEAD

Metadata retrieved using a HTTP HEAD request.

FILE

Metadata retrieved from a local file’s timestamp.

REMOTE

Metadata retrieved from an entity block generated by another agent.

Example

Method: REMOTE/REMOTE/GET/200

1. A first user agent retrieved the metadata on the document using a HTTP GET and got a 200 response code (GET/200).
2. A second user agent retrieved the first user agent’s Hina-Di file, then propagated it to its own file (REMOTE).
3. A third user agent retrieved the second user agent’s Hina-Di file, then propogated it to its own file (REMOTE).

Keyword

Words that can be used to give an overview of the document described by this entity block; tags, categories, etc. The value of this field is case-sensitive.

Keyword  = "Keyword" SEPARATOR keywords CRLF
keywords = TOKEN *(SEPARATOR TOKEN)

Image-Width

Width of an image described by an entity block, in pixels.

This field MUST NOT be used for entity blocks that do not describe images.

Image-Width = "Image-Width" SEPARATOR width CRLF
width       = DIGIT

Image-Height

Height of an image described by an entity block, in pixels.

This field MUST NOT be used for entity blocks that do not describe images.

Image-Height = "Image-Height" SEPARATOR width CRLF
height       = DIGIT

Experimental fields

Implementations MAY define custom fields with an X- prefix to provide additional metadata not covered in this specification. Implementations MUST NOT assume that all clients will use each of those fields. Clients that do not support any experimental field SHOULD ignore them.

Experimental-field = x-field-name SEPARATOR TOKEN
x-field-name       = "X-" WORD *("-" WORD)

Undefined fields

Any field that is not defined in this specification. Implementations that encounter such fields and do not support them SHOULD ignore them.

Undefined-field  = undef-field-name SEPARATOR TOKEN CRLF
undef-field-name = WORD *("-" WORD)

Encoding

The character encoding of the Hina-Di file SHOULD be specified as a parameter of the Content-Type field of the header block. If it is not specified, it defaults to EUC-JP.

Propagation

In Hina-Di, metadata propagation consists in acquiring metadata from other agents, then sharing it as it is in the user agent’s own Hina-Di file. This can be used for aggregation services or a peer-to-peer network.

The Authorized and Authorized-url fields allow indicating the user agent from which the metadata originally came from to help ensure its legitimacy. Propagating MUST only be performed if both fields are defined and if the user agent is trusted.

When propagating, all fields of an entity block defined in this specification, with the exception of experimental and undefined fields or of fields with empty values, MUST be reproduced without modification. Propagating experimental or undefined fields is not guaranteed. A header block, or any field that is part of it, MUST NOT be propagated.

The Method field MUST be processed according to the process described in the Method section.