Editing Astrophysics Data System (section)

==Search engine==
[[Image:A complex ADS search.png|thumb|right|An example of a complex search combining object, title and abstract queries with a date filter]]
Since its inception, the ADS has developed a highly complex [[search engine]] to query the abstract and [[Object database|object databases]]. The search engine is tailor-made for searching astronomical abstracts, and the engine and its [[user interface]] assume that the user is well-versed in astronomy and able to interpret search results which are designed to return more than just the most relevant papers. The database can be queried for author names, [[astronomical object]] names, title words, and words in the abstract text, and results can be filtered according to a number of criteria. It works by first gathering synonyms and simplifying search terms as described above, and then generating an "inverted file", which is a list of all the documents matching each search term. The user-selected logic and filters are then applied to this inverted list to generate the final search results.<ref name="search">{{cite journal |last1=Eichhorn |first1=G. |last2=Kurtz |first2=M.J. |last3=Accomazzi |first3=A. |last4=Grant |first4=C.S. |last5=Murray |first5=S.S. |year=2000 |title=The NASA Astrophysics Data System: The search engine and its user interface |journal=Astronomy and Astrophysics Supplement Series |volume=143 |issue=1 |pages=61–83 |doi=10.1051/aas:2000171 |bibcode=2000A&AS..143...61E |arxiv=astro-ph/0002102 |s2cid=2787647}}</ref>

===Author name queries===
The system indexes author names by surname and initials, and accounts for the possible variations in spelling of names using a list of variations. This is common in the case of names including accents such as [[Umlaut (diacritic)|umlaut]]s and transliterations from [[Arabic alphabet|Arabic]] or [[Cyrillic script]]. An example of an entry in the author synonym list is:

:''AFANASJEV, V''
:''AFANAS’EV, V''
:''AFANAS’IEV, V''
:''AFANASEV, V''
:''AFANASYEV, V''
:''AFANS’IEV, V''
:''AFANSEV, V''

===Object name searches===
The capability to search for papers on specific astronomical objects is one of ADS's most powerful tools. The system uses data from the [[SIMBAD]], the [[NASA/IPAC Extragalactic Database]], the [[International Astronomical Union]] Circulars and the [[Lunar and Planetary Institute]] to identify papers referring to a given object, and can also search by object position, listing papers which concern objects within a 10 [[arcminute]] radius of a given [[Right Ascension]] and [[Declination]]. These databases combine the many catalogue designations an object might have, so that a search for the [[Pleiades]] will also find papers which list the famous [[open cluster]] in [[Taurus (constellation)|Taurus]] under any of its other catalog designations or popular names, such as M45, the Seven Sisters or Melotte 22.<ref>{{cite web |url=http://doc.adsabs.harvard.edu/abs_doc/help_pages/search.html#SIMBAD/NED/LPI/IAUC_Object_Names/Position |title=SAO/NASA ADS HELP: Abstract Query Form |at=2.2.2.2 - SIMBAD/NED/LPI/IAUC Object Names/Position |publisher=Harvard-Smithsonian Center for Astrophysics |access-date=30 October 2008 |archiveurl=https://web.archive.org/web/20080509091500/http://doc.adsabs.harvard.edu/abs_doc/help_pages/search.html#SIMBAD/NED/LPI/IAUC_Object_Names/Position |archive-date=9 May 2008}}</ref>

===Title and abstract searches===
The search engine first filters search terms in several ways. An M followed by a space or [[hyphen]] has the space or hyphen removed, so that searching for [[Messier catalogue]] objects is simplified and a user input of M45, M 45 or M-45 all result in the same query being executed; similarly, [[New General Catalogue|NGC]] designations and common search terms such as [[Comet Shoemaker-Levy 9|Shoemaker Levy]] and [[T Tauri star|T Tauri]] are stripped of spaces. Unimportant words such as AT, OR and TO are stripped out, although in some cases [[case sensitivity]] is maintained, so that while '''a'''nd is ignored, '''A'''nd is converted to "[[Andromeda (constellation)|Andromeda]]", and '''H'''er is converted to "[[Hercules (constellation)|Hercules]]", but '''h'''er is ignored.<ref>{{cite web |url=http://doc.adsabs.harvard.edu/abs_doc/help_pages/search.html#Stop_Words |title=SAO/NASA ADS HELP: Abstract Query Form |at=2.2.1.2 - Stop Words |publisher=Harvard-Smithsonian Center for Astrophysics |access-date=30 October 2008 |archiveurl=https://web.archive.org/web/20080509091500/http://doc.adsabs.harvard.edu/abs_doc/help_pages/search.html#Stop_Words |archive-date=9 May 2008}}</ref>

===Synonym replacement===
Once search terms have been preprocessed, the database is queried with the revised search term, as well as synonyms for it. As well as simple [[synonym]] replacement such as searching for both [[plural]] and [[Grammatical number|singular]] forms, ADS also searches for a large number of specifically astronomical synonyms. For example, [[spectrograph]] and [[spectroscope]] have basically the same meaning, and in an astronomical context [[metallicity]] and [[Abundance of the chemical elements|abundance]] are also synonymous. ADS's synonym list was created manually, by grouping the list of words in the database according to similar meanings.<ref name="architecture"/>

As well as [[English language]] synonyms, ADS also searches for English translations of foreign search terms and vice versa, so that a search for the [[French language|French]] word ''soleil'' retrieves references to [[Sun]], and papers in languages other than English can be returned by English search terms.

Synonym replacement can be disabled if required, so that a rare term which is a synonym of a much more common term (such as '[[dateline]]' rather than '[[calendar date|date]]') can be searched for specifically.

===Selection logic===
The search engine allows selection [[logic]] both within fields and between fields. Search terms in each field can be combined with OR, AND, simple logic or [[Boolean logic]], and the user can specify which fields must be matched in the search results. This allows complex searches to be built; for example, the user could search for papers concerning [[NGC 6543]] OR [[NGC 7009]], with the paper titles containing (radius OR velocity) AND NOT (abundance OR temperature).

===Result filtering===
Search results can be filtered according to a number of criteria, including specifying a range of years such as "1945 to 1975", "2000 to the present day" or "before 1900", and what type of journal the article appears in [–] non-peer-reviewed articles such as [[academic conference|conference]] proceedings. These can be excluded or specifically searched for, or specific journals can be included in or excluded from the search.