6.7 beta 1: Bug in logic operators

Mark Barnes · October 2015

Either I'm very sleepy, or there's a bug in the way that Logos is interpreting logic operators and parentheses when searching in 6.7. Maybe it's always been like this. But it's very confusing when search logic works in some cases and not others.

Take a search for God love. That's identical to God AND love, to (God AND love) and to (God love). So far so good. In other words, if there's no operator, the AND operator is assumed.

By the same logic, (God love) OR (Jesus peace) should give exactly the same search results as (God AND love) OR (Jesus AND peace). It doesn't. You can see that the search fails to parse, and Logos is searching for "or" as if it was a word, not an operator

Equally, ((God AND love), (Jesus AND peace)) ought to give the same results, too. It doesn't. (I appreciate I should expect some difference in counting, but the results should be the same.)

On the other hand ((God love), (Jesus peace)) does return exactly the same results as ((God AND love), (Jesus AND peace)), as you would expect. But actually both search results are wrong (all four terms are being ANDed).

It appears that there are two bugs here:

The OR is not being recognised in (God love) OR (Jesus peace).
The comma is not recognised in ((God love), (Jesus peace)), or in ((God AND love), (Jesus AND peace)).

Graham Criddle · October 2015

Mark Barnes said:
Maybe it's always been like this.

I've just checked and I see the same behaviour on a 6.5 SR1 system I haven't updated yet.

Bradley Grainger (Logos) · October 2015

It's always been this way.

A malformed Boolean expression is interpreted as a "bag of words" (instead of giving an "INVALID QUERY TRY AGAIN!" error; see also Google). You can't infer that because the search engine interprets "(God love)" (standalone) as "God AND love" that it always has that meaning when used in any context in any other query.

We have plans to improve the feedback when you enter an "almost correct" Boolean query, perhaps with a "Did you mean...?" prompt.

Mark Barnes · October 2015

https://community.logos.com/discussion/comment/768485#Comment_768485

Bradley Grainger (Faithlife) said:
A malformed Boolean expression is interpreted as a "bag of words" (instead of giving an "INVALID QUERY TRY AGAIN!" error; see also Google). You can't infer that because the search engine interprets "(God love)" (standalone) as "God AND love" that it always has that meaning when used in any context in any other query.

That doesn't explain ((God AND love), (Jesus AND peace)) returns different results to ((God AND love) OR (Jesus AND peace)).

It's the former query that's interpreted incorrectly — the comma is being ignored (i.e. treated as an AND instead of an OR).

Does that mean you can't use parentheses within a list?

Bradley Grainger (Logos) · October 2015

https://community.logos.com/discussion/comment/769001#Comment_769001

Mark Barnes said:
That doesn't explain ((God AND love), (Jesus AND peace)) returns different results to ((God AND love) OR (Jesus AND peace)).

Yes, it does. The former query is not syntactically valid.

Mark Barnes said:
Does that mean you can't use parentheses within a list?

The limitation is that Boolean operators cannot be used within a list. The comma operator and OR are not interchangeable.

Mark Barnes · October 2015

https://community.logos.com/discussion/comment/769055#Comment_769055

Bradley Grainger (Faithlife) said:
The limitation is that Boolean operators cannot be used within a list.

Thanks for the clarification.

Anything you can do to alert users that their query may not have been interpreted correctly would be appreciated.

MJ. Smith · October 2015

https://community.logos.com/discussion/comment/769057#Comment_769057

Is this wiki accurate? (I just added the last sentence.

5. Lists

Lists are used to specify alternative search items in a compact form. For example (who, whoever, whom) is a list that will match who or whoever or whom.
Parentheses ( ) are optional in simple searches.

Note you must use a list with proximity operators e.g. (who, whoever, whom) NEAR Christ because (who OR whoever OR whom) NEAR Christ will give incorrect results.
Note you cannot use a list with logical operators as it will give incorrect results.

But this wiki is inaccurate?

Lists are a very useful feature which provide shortcuts in a number of searches. A list is written like this: (term1, term2, term3, etc.). When Logos encounters a list, it performs the search using just term1. Then it repeats the search using just term2, then with just term3, etc. Once it has finished, it then ORs the results. Here are some examples:

(Jesus, Christ) is equivalent to Jesus OR Christ
(Jesus, Christ) AND love is equivalent to (Jesus AND love) OR (Christ AND love)
(“My God”, “My Lord”) is equivalent to “My God” OR “My Lord”, showing that phrases can be used in a list.

Lists are most useful when used with fields (see below), or when trying to ensure proximity operators are only used in the outer terms of your search. For example:

The search described earlier (master NEAR love) OR (master NEAR serve) OR (neighbor NEAR love) OR (neighbor NEAR serve) can be simplified to (master, neighbor) NEAR (love, serve). Logos treats the two lists separately, iterating through them until every combination as been reached, like this:
- master NEAR love
- master NEAR serve
- neighbor NEAR love
- neighbor NEAR serve

Please note: Some people get confused as they equate the list with the OR command. They are not the same, even though in a very basic search they will perform in the same way. Remember, Logos iterates through lists, then ORs the results.