We are now entering Phase Two testing of a significant AskTrip upgrade. One of the biggest changes is the search system underneath the answer.
Until now, AskTrip has relied on a single search: our current lexical search. This is a keyword-based approach and, in our testing, it remains the strongest single method. But no single search catches everything, so we are moving to a three-search approach:
- Lexical v1 – the current search
- Lexical v2 – a second lexical search
- Vector search – a semantic search
The aim is not to replace the current system, but to improve coverage by adding other ways of finding relevant references.
What is changing?
- Lexical v1 is the current AskTrip search.
- Lexical v2 is also a lexical search, but it generates the search in a different way. Broadly, it is another keyword-based interpretation of the same question, designed to pick up papers that the current search might miss.
- Vector search works differently. Rather than relying mainly on matching words, it looks more at similarity in meaning. That means it can sometimes surface relevant documents even when they do not use the same terminology as the question. This was explained in more detail in an earlier blog post on vector search [Click here to read more about vector search].
So, in simple terms, lexical v2 gives us a different keyword route, while vector gives us a different semantic route.
What did the testing show?
We undertook a small sample of 10 questions to explore the differences between the search types, so the findings should be treated with caution.
Counting every reference found by each method, regardless of overlap:
- Lexical v1: 38
- Lexical v2: 33
- Vector: 22
So the current search, lexical v1, performed best overall.
But the more interesting finding is the number of references found only by one search type:
- Lexical v1 only: 6
- Lexical v2 only: 4
- Vector only: 2
This suggests two things.
First, lexical v1 is still the strongest single search.
Second, it still misses relevant material. Across this small sample, lexical v2 and vector together found 6 unique references that lexical v1 did not retrieve. In other words, the two new methods together contributed as many unique references as lexical v1 did on its own.
Lexical v2 appears to add value by improving coverage within the same general keyword-search approach. Vector adds value differently: it finds a smaller number of unique references, but may help when relevant papers are expressed in different language.
The bottom line
The current AskTrip search is good – but it is not complete.
Moving from one search to three should reduce the risk of missing relevant evidence. Lexical v2 helps broaden keyword retrieval, while vector search adds a more meaning-based layer.
The sample is small, so these results are only an early signal. But they are encouraging, and they support the move to a multi-search system.
If testing goes well, this new search system should be part of a significantly upgraded AskTrip in early May.
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