Last week we looked at the Anatomy of an Authority Record, but what if we look even deeper? Both Bibliographic and Authority records are essentially text, made up of characters formed either in MARC8 or UTF8. But what does that mean, and whats the difference?
The MARC-8 character set uses 8-bit characters, meaning it natively displays ASCII and ANSEL text. Because of the limitation of characters that this allows, the MARC-8 character set includes methods to extend the displayable characters. One method is to include both spacing base characters and nonspacing modifier characters (diacritics).
Spacing or nonspacing refers to cursor movement: a spacing character moves the cursor, a nonspacing character does not. A nonspacing character is always associated with a single spacing character, but multiple nonspacing characters may be associated with the same spacing character.
In MARC-8, when there is a nonspacing character, it precedes the associated spacing character: any cursor movement occurs after displaying the character. This method allows basic and extended Latin characters to be displayed using the default character set.
Another method MARC-8 uses to extend the displayable characters is to use alternate character sets. This is done by using escape sequences, special character sequences containing codes to indicate which character set is being selected for display. Possible alternate sets include subscripts, superscripts, Hebrew, Cyrillic, Arabic, and Greek. Chinese, Japanese and Korean are also possible by this method using EACC character encodings for these characters. While this method allows for many additional characters to be used, it is still limited and somewhat burdensome.
As computers needed to support a wider character set, many computer related companies formed a group to define the Unicode Standard. This standard is based on 16-bit characters. UTF-8 is a method of encoding these characters into sequences of from 1 to 3 bytes. Unicode, using the UTF-8 encoding, was accepted as an alternative character set for use in MARC records, with an initial limitation to using only the Unicode characters that have corresponding characters in the MARC-8 character set.
Unicode has definitions for nonspacing characters like MARC-8, except that the nonspacing character follows the character it modifies: cursor movement occurs before the character is displayed. Decomposed UTF-8 characters are similiar to MARC-8 diacritics, in which a base character is modified by one or more non-spacing characters. For example a base character ‘n’ with a non-spacing ‘~’ would combine to display ‘ñ’. Decomposed is also the current LC standard.
Unicode also includes many precomposed characters. These are spacing characters that are the equivalent of one or more nonspacing characters and a spacing character. A precomposed ‘ñ’, instead of having a base character and an additional non-spacing diacritic mark would combine all those elements into one code which represents the character with the diacritic as a whole. This causes a more difficult normalization routine.
To handle the various ways a composite character could be normalized, standardized normalization forms have been defined. These include NFD (Normalization Form Decomposed) and NFC (Normalization Form Composed). In NFD, every character that can be decomposed is converted to its most decomposed form following rules for canonical decomposition. In NFC, the characters are first decomposed as in NFD, then composed into precomposed (composite) forms following canonical rules. This may result in the sequence of characters for a given character changing to an alternate, equivalent form.
Many library systems are moving from MARC-8 to UTF-8 character encodings. This is a good move because it gives you the ability to accurately reflect the data, while lessoning the possibility of error. Backstage Library Works can return data in MARC-8, or UTF-8 (decomposed or composed) form.
Underneath the MARC records that we all know and love is a somewhat cryptic structure that tells our systems how to read the record. Luckily, this structure rarely gets corrupted, but when it does, it’s good to have a basic understanding of how to read and understand a MARC Format.
The MARC format is a text based format, meaning you can open it with a text editor. It is probably a good idea to only open a few (or only one!) record in a text editor, because it’s very difficult to read otherwise.
Every MARC record starts with a leader, the leader gives your system information about the record, including how big it is and what type of a record it is. Next is what is called a directory. Just like a normal directory, it tells you what tags are in it, and where the data for each tag is located.
This is how a leader is defined for a Bibliographic Record:
Leader: Position | Description | Explination ------------------------------------------ 00-04 | Record Length = This is how long the record is 05 | Record Status = Is the record new, changed or deleted 06 | Type of record = Authority, Book, Computer file, etc. 07 | Bibliographic level = Monograph/Serial/etc. 08 | Type of control = Archival or not 09 | Character coding scheme = MARC8 or UTF8 10 | Indicator count = # of indicators each tag has 11 | Subfield code count = # of subfield codes that make up 1 subfield 12-16 | Base address of data = The byte where actual record data begins 17 | Encoding level = Level of encoding/cataloging 18 | Descriptive cataloging form = AACR2 19 | Multipart resource record level = # (blank) 20 | Length of the length-of-field = # of bytes to store how long each tag is 21 | Length of the starting-character-position = # of bytes to store where tag begins 22 | Length of the implementation-defined portion = Rarely used 23 | Undefined = Not used
Looking at a leader can be confusing, but it’s also the only way to find some problems.
Here is an example record, as it may appear on your screen:
001 __ 3180021
005 __ 20050216201852.0
008 __ 040805s2005 nyu b 001 0 eng
010 __ ▼a 2004018260
020 __ ▼a0415971675 (alk. paper)
035 __ ▼a(DLC) 2004018260
040 __ ▼aDLC▼cDLC▼dDLC▼dCaONFJC▼dOrLoB-B
043 __ ▼an-us—
050 00 ▼aPS374.H56▼bO73 2004
082 00 ▼a813/.5409358▼222
090 __ ▼aPS374.H56▼bO73 2005
100 1_ ▼aOrbán, Katalin.
245 10 ▼aEthical diversions :▼bthe post-holocaust narratives of Pynchon, Abish, DeLillo, and Spiegelman /▼cKatalin Orbán.
260 __ ▼aNew York :▼bRoutledge,▼c2005.
300 __ ▼aix, 209 p. ;▼c24 cm.
440 _0 ▼aLiterary criticism and cultural theory
504 __ ▼aIncludes bibliographical references (p. 193-205) and index.
505 00 ▼gCh. 1.▼t”Mauschwitz” : monsters, memory, and testimony — ▼gCh. 2.▼tFamiliarity and forgetfulness in Walter Abish’s fiction — ▼gCh. 3.▼tPinpricks on the Ars(e) Narrandi : liminality and oven-games in Gravity’s rainbow.
600 10 ▼aPynchon, Thomas▼xKnowledge▼xHolocaust, Jewish (1939-1945)
600 10 ▼aSpiegelman, Art▼xKnowledge▼xHolocaust, Jewish (1939-1945)
600 10 ▼aAbish, Walter▼xKnowledge▼xHolocaust, Jewish (1939-1945)
600 10 ▼aDeLillo, Don▼xKnowledge▼xHolocaust, Jewish (1939-1945)
650 _0 ▼aAmerican fiction▼y20th century▼xHistory and criticism.
650 _0 ▼aHolocaust, Jewish (1939-1945), in literature.
650 _0 ▼aJudaism and literature▼zUnited States▼xHistory▼y20th century.
650 _0 ▼aWorld War, 1939-1945▼zUnited States▼xLiterature and the war.
650 _0 ▼aEthics in literature.
650 _0 ▼aJews in literature.
852 0_ ▼bkr▼hPS374.H56▼iO73 2005
856 41 ▼3Table of contents▼uhttp://www.loc.gov/catdir/toc/ecip0421/2004018260.html
949 __ ▼aApproval▼b1628024-35▼c67.20▼d1▼i20027328▼jUSD▼tBook
Now, if we are to take a look at the actual MARC structure, it looks like this (when looking at an underlying MARC record, you may not be able to see all of the special characters like end of field and end of record marks, but they are there):
01872cam a2200397 a 450000100080000000500170000800800410002501000170006602000280008303500220011104000360013304300120016905000240018108200
210020509000240022610000210025024501180027126000340038930000250042344000430044850400640049150502240055560000620077960000
620084160000600090360000590096365000590102265000500108165000660113165000650119765000260126265000240128885200280131285600
7801340949005601418 3180021 20050216201852.0 040805s2005 nyu b 001 0 eng a 2004018260 a0415971675 (alk. paper) a(DLC) 2004018260 aDLC cDLC dDLC dCaONFJC dOrLoB-B an-us— 00 aPS374.H56 bO73 2004 00 a813/.5409358 222 aPS374.H56 bO73 2005 1 aOrbán, Katalin. 10 aEthical diversions : bthe post-holocaust narratives of Pynchon, Abish, DeLillo, and Spiegelman / cKatalin Orbán. aNew York : bRoutledge, c2005. aix, 209 p. ; c24 cm. 0 aLiterary criticism and cultural theory aIncludes bibliographical references (p. 193-205) and index. 00 gCh. 1. t”Mauschwitz” : monsters, memory, and testimony — gCh. 2. tFamiliarity and forgetfulness in Walter Abish’s fiction — gCh. 3. tPinpricks on the Ars(e) Narrandi : liminality and oven-games in Gravity’s rainbow. 10 aPynchon, Thomas xKnowledge xHolocaust, Jewish (1939-1945) 10 aSpiegelman, Art xKnowledge xHolocaust, Jewish (1939-1945) 10 aAbish, Walter xKnowledge xHolocaust, Jewish (1939-1945) 10 aDeLillo, Don xKnowledge xHolocaust, Jewish (1939-1945) 0 aAmerican fiction y20th century xHistory and criticism. 0 aHolocaust, Jewish (1939-1945), in literature. 0 aJudaism and literature zUnited States xHistory y20th century. 0 aWorld War, 1939-1945 zUnited States xLiterature and the war. 0 aEthics in literature. 0 aJews in literature. 0 bkr hPS374.H56 iO73 2005 41 3Table of contents uhttp://www.loc.gov/catdir/toc/ecip0421/2004018260.html aApproval b1628024-35 c67.20 d1 i20027328 jUSD tBook
And here is a sample analysis of this record:
Leader: Position | Description | Data ------------------------------------------ 00-04 | Record Length = 01872 : confirmend in a hex editor the record is this length 05 | Record Status = c 06 | Type of record = a 07 | Bibliographic level = m 08 | Type of control = # (blank) 09 | Character coding scheme = a 10 | Indicator count = 2 11 | Subfield code count = 2 12-16 | Base address of data = 00397 : confirmed in hex editor this is correct 17 | Encoding level = # (blank) 18 | Descriptive cataloging form = a 19 | Multipart resource record level = # (blank) 20 | Length of the length-of-field portion = 4 21 | Length of the starting-character-position portion = 5 22 | Length of the implementation-defined portion = 0 23 | Undefined = 0
Directory: Tag | Field length | Starting character position 001 0008 00000 005 0017 00008 008 0041 00025 010 0017 00066 020 0028 00083 035 0022 00111 040 0036 00133 043 0012 00169 050 0024 00181 082 0021 00205 090 0024 00226 100 0021 00250 245 0118 00271 260 0034 00389 300 0025 00423 440 0043 00448 504 0064 00491 505 0224 00555 600 0062 00779 600 0062 00841 600 0060 00903 600 0059 00963 650 0059 01022 650 0050 01081 650 0066 01131 650 0065 01197 650 0026 01262 650 0024 01288 852 0028 01312 856 0078 01340 949 0056 01418| (56+1418 = 1474) 1474 = Ending field terminator below
Fields:
(For our convenience in readin the record we have replaced certain non-displayed fields with graphical representations)
| = field terminator (also used to terminate the directory)
$ = subfield code delimiter
^ = record terminator
_ = utf8 characters have been replaced by an undersore so the postions line up in a non-hex display
3180021|20050216201852.0|040805s2005 nyu b 001 0 eng | $a 2004018260| $a0415971675 (alk. paper)| $a(DLC) 2004018260| $aDLC$cDLC$dDLC$dCaONFJC$dOrLoB-B| $an-us—|00$aPS374.H56$bO73 2004|00$a813/.5409358$222| $aPS374.H56$bO73 2005|1 $aOrb__n, Katalin.|10$aEthical diversions :$bthe post-holocaust narratives of Pynchon, Abish, DeLillo, and Spiegelman /$cKatalin Orb__n.| $aNew York :$bRoutledge,$c2005.| $aix, 209 p. ;$c24 cm.| 0$aLiterary criticism and cultural theory| $aIncludes bibliographical references (p. 193-205) and index.|00$gCh. 1.$t”Mauschwitz” : monsters, memory, and testimony — $gCh. 2.$tFamiliarity and forgetfulness in Walter Abish’s fiction — $gCh. 3.$tPinpricks on the Ars(e) Narrandi : liminality and oven-games in Gravity’s rainbow.|10$aPynchon, Thomas$xKnowledge$xHolocaust, Jewish (1939-1945)|10$aSpiegelman, Art$xKnowledge$xHolocaust, Jewish (1939-1945)|10$aAbish, Walter$xKnowledge$xHolocaust, Jewish (1939-1945)|10$aDeLillo, Don$xKnowledge$xHolocaust, Jewish (1939-1945)| 0$aAmerican fiction$y20th century$xHistory and criticism.| 0$aHolocaust, Jewish (1939-1945), in literature.| 0$aJudaism and literature$zUnited States$xHistory$y20th century.| 0$aWorld War, 1939-1945$zUnited States$xLiterature and the war.| 0$aEthics in literature.| 0$aJews in literature.|0 $bkr$hPS374.H56$iO73 2005|41$3Table of contents$uhttp://www.loc.gov/catdir/toc/ecip0421/2004018260.html| $aApproval$b1628024-35$c67.20$d1$i20027328$jUSD$tBook|^
Ending field terminator = 1474
Record terminator position = 1475
Summary
———————————
Ending field position = 1475
Base address of data = 397
1475 + 397 = 1872 (Record Length)