Re: [rules-users] Condition syntax to access Map

2011/7/31 Mark Proctor <mproctor(a)codehaus.org&gt; Surely you mean that changes to Address should result in an update notification for the owning Person object. - But that's not what I meant. The LHS Person(...) alone fires due a Person inserted and not when an Address is inserted; it fires again if a Person() update is signalled. In contrast, Person() Address(...) fires after both have been inserted and again after *either one* has been updated. This "references" I doubt very much. Surely you can "insert" anything. And joins are possible on (primary key attributes as well. The notation a.b.c reflects an implementation technique for a hierarchical data type. (Traditionally, x-dot-y means "add the offset for y to the address resulting from x".) A more general concept for "navigation" in a data structure would have to separate a logical relationship from the implementation technique. It may be necessary to retain the "dot" notation for the hard coded access and to devise an entirely new notation for logical navigation. As a somewhat contrived example, assume that Address is stored as a map field with key "addr" and the street is the second text line of the address: declare Person name : String # default implementation as "JBean field" props : Map address : Address as props["addr"] # the implementation end declare Address lines : String[] street : String as lines[1] end Person( name == "Psmith", address/street == "Main Drag" ) Car( owner/address/street ... ) # Person owner Notice that explicitly using props["addr"] or lines[1] is just another implementation dependent notation which breaks as soon as someone decides to change it in the class. Such things should not permeate application code. Also, notice that a "navigation expression" could be dynamic, making navigation dependent on the object's state, or whatever. -W