The Estonian Subject Thesaurus is a universal controlled vocabulary in Estonian for indexing and searching various library material.
The official name of the thesaurus is "Eesti märksõnastik" and its official abbreviation is EMS. In English the thesaurus is called "Estonian Subject Thesaurus".

The subject terms from EMS are used
- in the online catalogue ESTER
- in the database of Estonian articles ISE
- in the union catalogue URRAM of the Estonian public libraries
- in various other catalogues and bibliographic databases of Estonia.

EMS includes about 61 000 preferred and nonpreferred terms. 

The Estonian Subject Thesaurus is managed by the Estonian Libraries Network Consortium, areas of responsibility are divided between libraries.

Format: Machine-readable MARC21:
Request syntax: https://ems.elnet.ee/teenus.php?vorming=M&sona=[keyword]
Sample request: https://ems.elnet.ee/teenus.php?vorming=M&sona=kaubamärgid

Format: Human-readable MARC21:
Request syntax: https://ems.elnet.ee/teenus.php?vorming=i&sona=[keyword]
Sample request: https://ems.elnet.ee/teenus.php?vorming=i&sona=kaubamärgid

Format: MarcXML:
Request syntax: https://ems.elnet.ee/teenus.php?vorming=X&sona=[keyword]
Sample request: https://ems.elnet.ee/teenus.php?vorming=X&sona=kaubamärgid

Format: Multiple-word subject terms:
Request syntax: https://ems.elnet.ee/teenus.php?vorming=I&sona=[keyword]+[keyword]
Sample request: https://ems.elnet.ee/teenus.php?vorming=I&sona=asutuste+arhiivid

All subject terms including a string(truncating mark %):
Request syntax: https://ems.elnet.ee/teenus.php?vorming=I&sona=%[keyword]%
Sample request: https://ems.elnet.ee/teenus.php?vorming=I&sona=%arhiiv%

Format: Record Marc21 Authority in machine-readable format (see https://www.loc.gov/marc/specifications/):
Request syntax: https://ems.elnet.ee/id/[keyword ID]#marc21
Sample request: https://ems.elnet.ee/id/EMS007185#marc21

Format: Record Marc21 in human-readable format (Marc21-I):
Request syntax: https://ems.elnet.ee/id/[keyword ID]#marc
Sample request: https://ems.elnet.ee/id/EMS007185#marc

Format: Record in MarcXML format (see http://www.loc.gov/standards/marcxml//):
Request syntax: https://ems.elnet.ee/id/[keyword ID]#xml
Sample request: https://ems.elnet.ee/id/EMS007185#xml

If the ID is in an inappropriate format,the answer is “Terms not found”:
Sample request: https://ems.elnet.ee/id/midaiganes#marc21
If the ID is in an appropriate format but no such ID is found or the term has been deleted, the answer is 0:
Sample request: https://ems.elnet.ee/id/EMS999999#marc21

Format: Machine-readable Marc21:
Request syntax: https://ems.elnet.ee/teenus.php?id=[ID]&vorming=M
Sample request: https://ems.elnet.ee/teenus.php?id=EMS005160&vorming=M

Format: Human-readable Marc21:
Request syntax: https://ems.elnet.ee/teenus.php?id=[ID]&vorming=I
Sample request: https://ems.elnet.ee/teenus.php?id=EMS005160&vorming=I

Format: MarcXML:
Request syntax: http://ems.elnet.ee/teenus.php?id=[ID]&vorming=X
Sample request: http://ems.elnet.ee/teenus.php?id=EMS005160&vorming=X

A field (except 00X fields) consists of the field number, two indicator positions and sub-fields for data content. An empty indicator position is marked by a slash. The sub-field sign consists of the sign $ and a letter or number. Below the most substantial elements are introduced, read more at https://www.loc.gov/marc/authority/ecadhome.html 

LDR  leader,e.g. 00000nza2200000n%00

001  control number which is EMS ID, e.g. EMS167171

003  code of the issuer of the control number ErEMS

008  fixed-length field for various coded info, the first 6 places indicate the compilation time of the record yymmdd, e.g. 130823|n|anznnbabn||n|

 040  compilation details of the record, do not vary: $aErEMS$best$cErEMS$fems

072  7 EMS subject field number where the term belongs, and EMS code, e.g. $a53$2ems

            The field can be repeated 

150  authorised thematic term, e.g. $ainfokeskkond

151  authorised geographic term, e.g. $aAbja-Paluoja

155  authorised form term, e.g. $aõigusaktid 

450, 451, 455  nonpreferred terms (synonyms) for authorised subject terms, e.g.450 $ainforuum; 451  $aAbja; 455 $anormatiivaktid 

450, 451, 455 9 English-language equivalents, e.g. 450 9 $ainformation environment; 451 9 $aNarva river; 455 9 $alegal acts 

550, 551, 555 related subject terms and their URLs on sub-field $0

$wg – broader term

$wh – narrower term

$w missing – other semantic connection

nt

150  $aalalõualuu

450  $amandibula

450  9$amandible

550 $wg$alõualuud$0https://ems.elnet.ee/id/EMS029481

550  $wh$aalalõuapõnt$0https://ems.elnet.ee/id/EMS149978

550 $aalalõualiiges$0https://ems.elnet.ee/id/EMS147267 

670    source, e.g. $aRegio Eesti Teede Atlas,Regio, 1998.

680  explanation with the sub-field symbol $i, e.g. $iIsikute, organisatsioonide ja süsteemide kogum, milles kogutakse, töödeldakse ja levitatakse infot. Hõlmab ka informatsiooni ennast.

The subject thesaurus is constantly updated and can be downloaded in both MARC21 and MARCXML formats.

Machine-readable MARC21: link

Human-readable MARC21: link

MarcXML: link