Report:Delphion/Search Syntax/Allowed Operators/Truncation or Wildcard Operators
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Truncation Operators
Delphion offers two truncation operators: the unlimited truncation, represented by an asterisk (*), and the single-character wildcard, (?). The search engine supports both left and right-hand truncation, but there are some limits on left-handed truncation: in the German Application and German Granted files, unlimited left hand truncation (*) is supported. For all other files, single-character truncation (?) is supported, and the user has to define how many wildcards to use.
Left-handed keyword truncation is especially important in the chemical and biochemical arts, where chemical names can have varying prefixes. The lack of unlimited left-hand truncation in Delphion can be seen as a drawback in this respect; however, because fixed-character truncation is possible, keyword queries can still be designed to be as broad as necessary by using multiple ?’s. The Delphion help file gives the following example:
- ???oxide
Will return, for example:
- monoxide
- peroxide
- hexoxide
- alkoxide
- suboxide
- trioxide
- ethoxide
But will NOT return, for example:
- hydroxide
- nioboxide
The bottom line is, because left-hand truncation must be defined to include a limited number of characters, careful thought must go in to designing keyword strings to ensure that all possible variations of interest will be covered by the defined truncation.
Editor's Note:In contrast to Delphion's truncation options, some competitor search systems offer unlimited left and/or internal truncation in all collections, while others do not offer it at all. Left truncation can be especially important to chemical and biotechnology searchers, who often deal with keyword terms that may have multiple prefixes. Users should be careful to evaluate these wildcard options carefully.
Stemming
Delphion is also unusual in that it automatically applies stemming to all keywords (or phrases, meaning combinations of words without operators between them). In order to search an exact word or phrase in Delphion, the user needs to enclose it in quotes; otherwise, stemming will be automatically applied.
Editor's Note:Some may find the automatic stemming inconvenient, as it returns a larger number of hits and perhaps not all the variations of the word are of interest (for example, a search on “composite” can return a hit for the word “composition,” which may not be of interest). However, in most cases this feature is an advantage as 1) the feature can be turned off if necessary, and 2) it can return hits for grammatical variations of a word that maybe the searcher didn’t think to include in the search strategy, but might still be relevant.
