Among patent priorities a special cathegory is technical realtionships.
In Patstat Manual the definition of TLS205_Tech_rel is “patents which have been technically linked by patent examiners on the basis of similar content” and this gives as really few information about the kind of patents under examination.
It could be very interesting understand if there is a difference between the patents contained in the TLS_212_CITATION as cited patents and the ones contained in the TLS205_TECH_REL as patents with a technological relationship with a patent of reference.
To investigate this issue I started taking all the appln_id of the reference patent in both tables, and then I checked if there was a correspondence between the cited patents and the patent with a technological relationship. The result is that on 2400000 records contained il TLS205 just 800 appear in both tables.
But if we read the description of the DOCDB and INPADOC family we see that the fact that some patents are group in this particular way “means that most probably the applications share exactly the same priorities (Paris Convention or technical relation) as in table TLS204_PRIOR_APPLN and TLS205_TECH_REL and tls216_APPLN_CONTN”. So this sentence gives us a real clue about the kind of patent that we are handling (even if it could be argued that including technical realtionship in family definition could give a bias since it's defined by examiner).
Another tool that provide information about this table is the Link Method Indicator (LMI ) also called priority-linkage-type. It answers at the question: “Is the document-id in application-reference = document-id in the prioritiy-claim data-format="docdb", ignoring the filing-date? ” with a NO, case #5 that means that exists a technical relation between the two patents adding a note in which it is explained that the “technically related documents are those patent documents whose technical content has been identified within the EPO as being considered equivalent”.
So I can conclude that all the patents contained in TLS205_TECH_REL are very useful to study the duplication of patents.