Proximity Operators

After return to the Commander window, the reaction retrieval may be executed separately 629 Dicls-Aldcr reactions between aliphatic dienes and cyclic dicno-pliiles are found. This partial result can be narrowed down by restricting tlie reaction conditions by means of the fact editor, The search field codes for the yield and the temperature can be found to be RX.NYD and RX.T, respectively, either by browsing the database structure or by applying the Find option, as described in the first example. To ensure that the retrieved reaction conditions belong to the same experiment, both search terms must be connected by means of the PROXIMITY operator. Before the retrieval is started, the option "Refine results in... 

It is often possible to search for bands of particular intensity in selected wavelength ranges. During the search all fields may be interconnected logically (search masks) or by logic operators (and or not proximity operators). A summary of information contained in a spectral data bank for a given compound is given in Tab. 22.3. 

Missions to the planets of onr solar system and their satellites will increasingly require the greatest possible productivity and scientific return on the large investments already made in the development and lannch of these sophisticated spacecraft. Particular destinations, such as the seas of Emopa, will place great demands on autonomous systems, which will have to conduct independent explorations in environments where communication with Earth is difficult or impossible. Proposed missions to near-Earth objects (NEOs) will entail autonomous rendezvous and proximity operations, and possibly contact with or sample retrieval from the object. 

The internal structure of a full-text database is significantly different from that of other types such as relational (row/column/table-oriented) or object-oriented databases. The domain of a full-text database is the indexing and storage of large amounts of textual data. Indexes based on words occurring in the text corpus, proximity operators to locate phrases and close spatial relationships between words, and probabilistic thesauri to define word, concept, and content clusters are important characteristics of this type of database. See Bibliographic Database Object-oriented Database Object-Relational Database Relational Database and Textual Database. 

Boolean Logical Operators and Other Proximity Operators... 

Along with AND, OR and NOT there are more operators for restricting a query. Using Boolean logic, the distance between search terms is not defined. In many cases it will be necessary to determine more precisely the proximity between two search terms in order to catch them in the same context. Other important proximity operators are listed below ... 

The number of documents increases with the distance between the search terms. Simultaneously the number of relevant documents declines because a relation between the search terms is no longer given. Proximity operators are vital especially for full-text and factual databases. 

In the field CN, proximity operators are not allowed for searching, but truncation is possible. The search term must be entered exactly as it is entered in the database record, inch brackets, hyphens and blanks. The field is phrase-indexed. There is one document for every substance. The simplest search is the search with a trade name ... 

In this case again the index should be consulted in order to find out whether a Heading Parent was retrieved. As every compound can only have one Heading Parent a combination of several Heading Parents through the use of proximity operators is excluded. 

The Basic Index contains every name segment of the CA Index Names and of every synonym. Basic Index searching inevitably requires the use of proximity operators. 

The system does not distinguish between small and capital letters. Search terms that are misunderstandable should be entered with spaces as in the case of Co and CO. The MF field is phrase-indexed and proximity operators are not allowed for searching. 

Other databases contain other stopword lists. The combining of search terms in the Basic Index is done through the Boolean operators AND, OR, NOT and proximity operators W, A, S, L and P (Sect. 6.2.3.5). 

As explained in Sect. 6.2.3, queries may be formulated with Boolean and proximity operators. The LINK operator is crucial regarding the search among Index Terms. It enables one to search for terms found within the same unit, i.e. within the same Index Term. 

The field Author (AU) may contain up to ten names of authors for every publication, or inventors names for patents. The field is phrase-indexed, proximity operators cannot be used. The surname comes first and given Christian names and/or initials always follow. 

The field Corporate Source (CS) names the organisation/institution where a publication was produced, or, in the case of a patent, the patent assignee(s). In this field, proximity operators are allowed, as the paragraph is single-word indexed. 

Since mid-1992 the system allows 30 letters for the inventor s name and three initials for Christian names. The field is phrase-indexed and thus not searchable with proximity operators. 

CAS abbreviations are transcribed into spellout versions, e.g. PREPN becomes PREPARATION (Fig. 171). A computer program splits all substance names into the smallest possible fragments. On the one hand, this feature allows easy retrieval of chemical names and name fragments, on the other hand, when a search for exact names is conducted, one must be ensure using the command language that name fragments are not retrieved. ESA-IRS has introduced a new proximity operator (T), restricting the terms to those that are parts of the same word. 

As on ESA-IRS, the chemical names are split into their possible fragments by a computer program. In order to offer search strategies that are similar to ESA-IRS, the proximity operator C was introduced. 

Proximity operators define the distance between the search terms, e.g. if they are next to each other or within a predefined distance, sentence or field. Also called context operators. 

Singfe-word inverted multiword-terms written with hyphen, are divided in single words. They must be searched with -> proximity operators without special charcters. 

Special characters e.g. hyphen and apostrophe, which are normally eliminated during indexing. Words in the document with a hyphen must be searched with proximity operators. The terms are single-word inverted. An exception are -y keyword list and -y thesaurus. 

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