When I throw such a query at my server, Mike Taylor's CQL parser reports that it didn't expect that second equal sign in the middle of the term it was processing. That suggests to me that you've inferred a missing Boolean, but the query grammar supports other options.
Proper query: http://viaf.org/viaf/search?query=local.names+%3D+ralph+and+local.personalNames+%3D+levan&httpAccept=text/xml
Query missing "and": http://viaf.org/viaf/search?query=local.names+%3D+ralph+local.personalNames+%3D+levan&httpAccept=text/xml
Either way, the general "query syntax error" gets returned.
I'm a little nervous about fixing users' queries for them. You don't know for a fact that the problem was actually a missing Boolean or that the missing Boolean was an "and". Too often I'm getting queries from robots and if they don't get told they have a problem, their code will never get fixed.
On a side note, when I clicked on the URL provided, I get an error 68, which is about sending records and authentication. Since I didn't send a record, I'd think that diagnostic 3 (authentication error) would have been more appropriate.
> -----Original Message-----
> From: SRU (Search and Retrieve Via URL) Implementors
> [mailto:[log in to unmask]] On Behalf Of J. Rupp
> Sent: Friday, July 07, 2017 5:50 AM
> To: [log in to unmask]
> Subject: SRU/CQL: Diagnostics Relating to CQL
> Dear Sir and Madam
> We have a question about diagnostics relating to CQL
> (https://www.loc.gov/standards/sru/diagnostics/diagnosticsList.html) and
> the proper behavior of the API regarding missing “boolean operator”.
> For example the correct request/query:
> The wrong one (boolean operator “and” missing):
> 1. What is the correct diagnostic number/description relating to a missing
> “boolean operator”?
> 2. Is it allowed that our SRU-API detects a missing boolean oprator and add
> “and” as boolean operator automatically?
> Thank you!
> If you have any further questions, please do not hesitate to contact me.
> Yours sincerely,
> on behalf of Deutsche Nationalbibliothek (German National Library) Jochen
> *** Reading. Listening. Understanding. German National Library ***
> Jochen Rupp
> Deutsche Nationalbibliothek
> Digital Services
> Adickesallee 1
> 60322 Frankfurt am Main