diff --git a/idl/pEpACIDLang.yml2 b/idl/pEpACIDLang.yml2
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+// p≡p API Y language
+
+// Copyleft (c) 2019-2020, p≡p foundation
+// this file is under GNU General Public License 3.0
+// see LICENSE.txt
+
+// written by Volker Birk and Nana Karlstetter
+
+decl package @name;
+decl api @name;
+
+decl type @name;
+decl is @type;
+decl extends @type;
+
+// enum
+decl enum @name;
+decl item @name;
+decl hex is item (output=hex);
+
+// struct
+decl struct @name;
+decl field @type @name;  // optional: function=free for a free function
+
+// method
+decl method @name;
+
+
+// unimplemented
+// decl internal < field >; // internal field, p≡p engine only
+// decl flag @name;
+
+// decl protocol @name;
+// decl construct, new is construct;
+
+// readonly in parm, ownership remains with caller
+decl use @type @name (mode=use) alias parm;
+
+// inout parm, ownership remains with caller
+decl supply @type @name (mode=supply) alias parm;
+
+// in parm, ownership goes to callee
+decl provide @type @name (mode=provide) alias parm;
+
+// out parm, ownership goes to caller
+decl return @type @name (mode=return) alias parm;
+
+// factory delivers this, ownership goes to caller
+decl create @type @name (mode=create) alias parm;
+
+decl throws @except;
+decl caveat(mode=caveat) alias doc;
+
+
+// base types
+
+// string       text  
+//              p≡p engine uses UTF-8 strings which are NFC normalized. 
+//              Cf. https //dev.pep.foundation/Engine/Basic%20Concepts%20of%20the%20pEp%20Engine
+// binary       binary data
+// int          signed integer number
+// uint         unsigned integer number
+// size         size in memory
+// bool         true or false
+// timestamp    point of time
+// opaque       opaque type (was: 'any')
+
+//package idl {
+//    type string;
+//    type binary;
+//    type int;
+//    type uint;
+//    type size;
+//    type bool;
+//    type timestamp;
+//    type opaque;
+//}
+
+// collections
+// list     one or more elements, which have a sequence
+// set      one or more elements, which do not have a sequence
+// pair     two elements in sequence
\ No newline at end of file