Search
Search instrutions
The PHG Foundation search engine returns results from all text and databases stored on the PHG Foundation site [unless you restrict your search with the resource limiter].
There are two types of search available via this engine
Information about these searches is set out below.
In both natural language and Boolean searches you can narrow search scope using specific search limiters as described below.
Natural language searching
This is a basic, ‘convenient’ and quick search.
To undertake a natural language search, just type the words you are looking for into the textbox. e.g. ‘genetic testing insurance’.
The search program will automatically return what it considers to be the best results.
Natural language searches are optimised for speed and relevance ranking. Because of this there are some limitations:
- Common words are ignored. For example ‘the’, ‘some’, ‘at’ are considered to have zero semantic value and the search-engine ignores them. This is because there are so many of these that the crawler would slow down significantly.
- Words of less than 3 letters are ignored. Thus ‘DNA’ will return results but ‘OU’ will return none. Again this is for speed and resource purposes.
- Whole words only. The search engine only indexes whole words; partial word searches will not return any results.
Result Ranking. Natural language searches are optimised to produce the most relevant ranked results based upon both the frequency and location of words in a document.
You can override the ranking using a search limiter.
The engine accepts any true word characters (letters, digits and underscores). Note: Single apostrophes (') are accepted; more apostrophes than this will be stripped by the parser.
Tips
-
Start with fewer words and then focus your search by adding more words or limiters to focus/improve your results.
- Avoid using apostrophes unless you have to : i.e. “Alzheimer’s” will probably return less results than “Alzheimer”.
Boolean searching
Boolean searching allows the use of logical commands (called ‘Boolean operators’) to limit or focus the scope of a search.
Two of the most useful Boolean operators are:
- Quotation marks around your search terms to search only for that exact phrase, and
- An asterisk as a wildcard character at the beginning or end of your search term
A full list of available Boolean operators is set out in the below table.
|
Operator |
Meaning |
|
+[word] |
The word is mandatory in all rows returned |
|
-[word] |
The word cannot exist in that record |
|
>[word] |
The word has higher relevance than other words in the string |
|
<[word] |
The word has less relevance than other words in the string |
|
~[word] |
The tilde operator gives a word a negative score. Note: It can be easily confused with the ‘<’ or ‘-’ operators. · Unlike the ‘-’ operator the word is still allowed to be in the record. · Unlike the '<' operator, which gives a reduced, yet still positive score (e.g 0.5%), the tilde ~ actually minuses from the overall score (e.g –1%) where the word is in the record. |
|
[partial word]* |
The wildcard may be used at the beginning or end of the word to match any longer words containing this word. · e.g. ‘*gene’ would match ‘transgene’ but not ‘genetic’ and ‘gene*’ would do the opposite. |
|
([word(s)/phrase(s)]) |
Parentheses are used to demarcate a sub-expression. e.g ‘>(testing insurance) |
|
“[phrase]” |
Only records matching the exact phrase between quotes will be returned. |