MARC 21 Format for Classification Data: 856: Electronic Location and Access (Network Development and MARC Standards Office, Library of Congress)

Information needed to locate and access electronic information. The field may be used in a classification record for a resource when that resource or a subset of it is available electronically. In addition, it may be used to locate and access an electronic version of a non-electronic resource described in the classification record or a related electronic resource. This field may also be used to link to an electronic resource intended to supplement the classification scheme, e.g. an image of a map.

Field 856 is repeated when the location elements vary (the URL in subfields $a, $b, $c when used). It is also repeated when more than one access method is used, mirror sites are recorded, different formats/resolutions with different URLs are indicated, and related items are recorded.

GUIDELINES FOR APPLYING CONTENT DESIGNATORS

■ INDICATORS

First Indicator - Access method

Defines the access method to the electronic resource. The value in this indicator position determines which subfields are appropriate.

If the resource is available by more than one access method, the field is repeated with data appropriate to each method. The methods defined are the main TCP/IP (Transmission Control Protocol/Internet Protocol) protocols.

When recording a URL in subfield $u, the value corresponds to the access method (URL scheme), which is also the first element in the URL string.

# - No information provided

Used when subfield $g contains a URN and there is no URL recorded in subfield $u. When subfield $u contains a URL and subfield $g is also present with a URN, the indicator value for the appropriate access method of the URL is given.

0 - Email

Access to the electronic resource is through electronic mail (email). Includes subscribing to an electronic journal or electronic forum through software intended to be used by an email system.

1 - FTP

Access to the electronic resource is through the File Transfer Protocol (FTP).

2 - Remote login (Telnet)

Access to the electronic resource is through remote login (Telnet).

3 - Dial-up

Access to the electronic resource is through a conventional telephone line (dial-up). Additional information in subfields of the record may enable the user to connect to the resource.

4 - HTTP

Access to the electronic resource is through the Hypertext Transfer Protocol (HTTP).

7 - Method specified in subfield $2

Access to the electronic resource is through a method other than the defined values and for which an identifying code is given in subfield $2 (Source of access).

Second Indicator - Relationship

Relationship between the electronic resource at the location identified in field 856 and the entity described in the record. Only value # (no information provided) is used for classification records.

# - No information provided

0 - Resource

1 - Version of resource

2 - Related resource

8 - No display constant generated

■ SUBFIELD CODES

$b - Access number

Access number associated with a host. Can be an Internet Protocol (IP) numeric address , or a telephone number if dial-up access is provided through a telephone line. This data changes frequently and may be generated by the system, rather than statically stored.

May be repeated if all the other information in the field applies.

$f - Electronic name

Electronic name of a file as it exists in the directory/subdirectory indicated in subfield $d on the host identified in subfield $a. Subfield $f may be repeated if a single logical file has been divided into parts and stored under different names. In this case, the separate parts should constitute a single bibliographic item. In all other cases, a file that may be retrieved under different filenames contains multiple occurrences of field 856, each with its corresponding electronic name in subfield $f. A filename may include wildcard characters (e.g., * or ?) if applicable. Use subfield $z to explain how files are named, if needed.

$k - Password

Password required to access the electronic resource. An FTP site may require the user to enter an Internet Protocol address or may require a specific password. Electronically accessed catalogs may also require a password. If a system that requires a password will accept anything entered as valid, this subfield can be omitted from field 856. This subfield is used to record general-use passwords, and should not contain passwords requiring security. Textual instructions about passwords are contained in subfield $z (Public note).

$l - Logon

Characters needed to connect (i.e., logon, login, etc.) to an electronic resource or FTP site. Used to record general-use logon strings which do not require special security.

For many general-use File Transfer Protocol servers, access is gained by entering the string "anonymous." An account number required for login may also be indicated.

$q - Electronic format type

Identification of the electronic format type, which is the data representation of the resource, such as text/HTML, ASCII, Postscript file, executable application, or JPEG image. Electronic format type may be taken from enumerated lists such as registered Internet Media Types (MIME types).

The intent of specifying this element is to provide information necessary to allow people or machines to make decisions about the usability of the encoded data (what hardware and software might be required to display or execute it, for example). The electronic format type also determines the file transfer mode, or how data are transferred through a network. (Usually, a text file can be transferred as character data which generally restricts the text to characters in the ASCII (American National Standard Code for Information Interchange (ANSI X3.4)) character set (i.e., the basic Latin alphabet, digits 0-9, a few special characters, and most punctuation marks) and text files with characters outside of the ASCII set, or non-textual data (e.g., computer programs, image data) must be transferred using another binary mode.)

$r - Settings

Settings used for transferring data. Included in settings are: 1) Number Data Bits (the number of bits per character); 2) Number Stop Bits (the number of bits to signal the end of a byte); and 3) Parity (the parity checking technique used). The syntax of these elements is:

If only the parity is given, the other elements of settings and their related hyphens are omitted (i.e., <Parity>). If one of the other two elements is given, the hyphen for the missing element is recorded in its proper position (i.e., <Parity>--<Number Stop Bits> or <Parity>-<Number Data Bits>- ). The values for parity are: O (Odd), E (Even), N (None), S (Space), and M (Mark).

$s - File size

Size of the file as stored under the filename indicated in subfield $f. It is generally expressed in terms of 8-bit bytes (octets). It may be repeated in cases where the filename is repeated and directly follows the subfield $f to which it applies. This information is not given for journals, since field 856 relates to the entire title, not to particular issues.

$u - Uniform Resource Identifier

Uniform Resource Identifier (URI), which provides standard syntax for locating an object using existing Internet protocols. Field 856 is structured to allow for the creation of a URL from the concatenation of other separate 856 subfields. Subfield $u may be used instead of those separate subfields or in addition to them. Subfield $u may be repeated only if both a URN or a URL or more than one URN are recorded.

May be repeated only if both a URN and a URL or more than one URN are recorded. Field 856 is repeated if more than one URL needs to be recorded.

$v - Hours access method available

Hours that access to an electronic resource is available at the location indicated in this field. If the record is for a system or service, the hours of availability are recorded in field 307 (Hours, etc.). This subfield is only used to record hours of availability of the specific location indicated in field 856.

$w - Record control number

System control number of the related record preceded by the MARC code, enclosed in parentheses, for the agency to which the control number applies. The data in the subfield links field 856 to the MARC record having the same data in a control number field. See Organization Code Sources for a listing of organization code sources used in MARC 21 records.

$y - Link text

Used for display in place of the URL in subfield $u (Uniform resource identifier). When subfield $y is present, applications should use the contents of it as the link instead of subfield $u linking to the destination in subfield $u.

Use of the link text is independent of any decision concerning the second indicator value.

■ EXAMPLE


084	0#$alcc [Library of Congress Classification]
153	##$aG1350$cG1352$hAtlases$hBy region or country$hAmerica. Western Hemisphere$hNorth America$hUnited States$hNortheastern States. Eastern United States, 1870 and later$hSouthern States. Confederate States of America$hSouth Central States$jWest South Central States
856	7#$uhttp://minaret.loc.gov/images/gschedule/G1350a.gif$yMap of West south central states [The 856 field links to an image file related to the G schedule (Geography; Maps; Anthropology; Recreation), which consists of a map with references to classification numbers that cover particular areas.]

INPUT CONVENTIONS

Spacing underscore and tilde in URLs - In February 1994, additional characters in the MARC character set were defined to both accommodate existing bibliographic needs and to align it with the ASCII and ANSEL character sets. Both the spacing underscore and the spacing tilde were added at the time because of the need in directory and file names for electronic resources.

Many systems have implemented these characters, however, for systems that have not implemented the spacing underscore and tilde, the following alternative characters may be used:

%5F for spacing underscore

%7E for spacing tilde

Style for Recording Telephone Numbers - In subfield $b, periods, spaces, and parentheses used to divide the portions of a number are replaced with hyphens. Numbers are recorded as follows:

Exchange/line number portion often includes internal separators which are replaced by hyphens. If an extension is also given, it is appended to the telephone number preceded by a space and " x".


856	3#$b1-202-7072316$j2400/9600$nLibrary of Congress, Washington, DC$oUNIX$rE-7-1$tvt100$zRequires logon and password

CONTENT DESIGNATOR HISTORY

$g - Uniform Resource Name [OBSOLETE, 2000]
Because subfield $g (Electronic name - End of range) was rarely if ever used, it was redefined as Uniform Resource Name in 1997. It was subsequently made obsolete in favor of recording the URN in subfield $u.
$u - Uniform Resource Identifier [RENAMED, 2000]
Prior to 1999, subfield $u was defined as Uniform Resource Locator and was repeatable. It was changed to not repeatable because of ambiguity in determining when the subfield could be repeatable. Subfield $u was changed back to repeatable and renamed Uniform Resource Identifier in 2000 to record both URLs and URNs after subfield $g was made obsolete.
$y - Link text [NEW, 2000]

856 - Electronic Location and Access (R)