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commercial websites' price sorting

### Program Information

Name: commercial websites' price sorting
Domain: web service and application
Functionality: help the users to sort the commercial good according to price
Input: q: a search criterion c: a sorting criterion s(q,c): a perfect search function
Output: Pages(s(q,c)): the results that the search engine return

#### Reference


Metamorphic Relations for Enhancing System Understanding and Use
https://dx.doi.org/10.1109/TSE.2018.2876433


### MR Information

#### MR1------

Description:
Property: Let $s(q, c)$ denote a perfect search function, where $q$ is a search criterion and $c$ is a sorting criterion — the results are sorted according to c. If $c1 (c2)$ denotes the criterion that sorts the results by price in ascending (descending) order, then $s(q, c1)$ and $s(q, c2)$ should return exactly the same set of results, but in reverse order.
Source input: $q_{s}$, $c_{s}$, $s_{s}(q_{s}, c_{s})$
Source output: $Pages(s_{s}(q_{s}, c_{s}))$
Follow-up input: $q_{f}$, $c_{f}$, $s_{f}(q_{f}, c_{f})$
Follow-up output: $Pages(s_{f}(q_{f}, c_{f}))$
Input relation: $q_{s}\equiv q_{f}$, $c_{s}(c_{f})$ denotes the criterion that sorts the results by price in ascending (descending) order
Output relation: $Pages(s_{s}(q_{s}, c_{s}))=Pages(s_{f}(q_{f}, c_{f}))$
Pattern: symmetry, change direction, add noise
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