imported from GitHub issues: https://github.com/wbstack/queryservice-ui/issues/4

GreenReaper:
If I type wdt:[CTRL+SPACE] (or wd:/ps: etc.) I get a popup box offering to autocomplete an entity. I can type P1 or Q2 and get results - but they're _local_ results, not Wikidata results. This is cool… but it isn't right, as that PREFIX isn't redefined in the query.

Conversely, using prefixes that _are_ defined in the query, and refer to local entities, doesn't work:

Unknown prefix 'wfd:'.

Similarly, mousing over wdt:P6 gives a popup with data on the local P6, even though it will actually use another P6.

This may mislead the user into writing [queries that run, but not as expected](https://furry.wikibase.cloud/query/sparql?explain&query=%23defaultView%3ATable%0A%0APREFIX%20wfd%3A%20%3Chttps%3A%2F%2Ffurry.wikibase.cloud%2Fentity%2F%3E%0APREFIX%20wfdt%3A%20%3Chttps%3A%2F%2Ffurry.wikibase.cloud%2Fprop%2Fdirect%2F%3E%0APREFIX%20wfp%3A%20%3Chttps%3A%2F%2Ffurry.wikibase.cloud%2Fprop%2F%3E%0A%0ASELECT%20%3FitemLabel%20%3FcreationDate%20(CONCAT(%22https%3A%2F%2Fen.wikifur.com%2Fw%2Fimages%2F%22%2C%20substr(%3FlogoMD5%2C%201%2C%201)%2C%20%22%2F%22%2C%20substr(%3FlogoMD5%2C%201%2C%202)%2C%20%22%2F%22%2C%20%3FlogoFileName)%20AS%20%3FlogoURL)%0AWHERE%0A%7B%0A%20%20%20%20%3Fitem%20wfdt%3AP2%20wfd%3AQ2%20.%0A%20%20%20%20%3Fitem%20wdt%3AP6%20%3FcreationDate%20.%0A%09SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22%5BAUTO_LANGUAGE%5D%2Cen%22%20%7D%0A%20%20%20%20OPTIONAL%20%7B%0A%20%20%20%20%20%20%3Fitem%20wfdt%3AP15%20%3FlogoFileName.%0A%20%20%20%20%20%20BIND(MD5(%3FlogoFileName)%20as%20%3FlogoMD5).%0A%20%20%20%20%7D%0A%7D), because the query service uses Wikidata as wdt:.

The situation is different to e.g. the Wikibase Registry where [wdt: has been modified](https://wikibase-registry-query.wmflabs.org/proxy/wdqs/bigdata/namespace/wdq/sparql?explain&query=%23defaultView%3ATimeline%0ASELECT%20%3Fitem%20%3FitemLabel%20%3FcreationDate%20(SAMPLE(%3Flogo)%20AS%20%3Fimage)%0AWHERE%0A%7B%0A%20%20%20%20%3Fitem%20wdt%3AP11%20wd%3AQ20%20.%0A%20%20%20%20%3Fitem%20wdt%3AP5%20%3FcreationDate%20.%0A%09SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22en%2Cen%22%20%7D%0A%20%20%20%20OPTIONAL%20%7B%20%3Fitem%20wdt%3AP8%20%3Flogo%20%7D%0A%7D%0AGROUP%20BY%20%3Fitem%20%3FitemLabel%20%3FcreationDate). (I don't think doing this is a good idea.)

Ideally, autosuggest would use prefixes defined by the server, modified by any PREFIX within the query - but this may not be easy. Perhaps using the new way of adding local prefixes would be helpful? It might also lead to fragmentation and incompatible queries. Adding such site prefixes automatically (if defined) might at least give a strong hint that you should declare them to use them.