ignal would have been discarded. 246 Validation of Communications Systems with SDL process DLC (0, maxDLC + 1) FPAR me DLCident, originator Boolean connected V76frame (V76para) V76para ! present ( DISC) V76frame CALL CRCok (UA : (. me .) (V76para) ! !CRC) basic block 11 VIA peer DLCstopped True ) False L Datalnd (me, V76para! I ! da'a) Figure 7.60 The basic block number 11 never executed in process DLC process DLC (0, maxDLC + 1) FPAR me DLCident, originator Boolean waitUA V76frame (V76para) V76para ! present basic block 15 ( UA ) RESET (T320) DLCstopped L_EstabConf connected Figure 7.61 The basic block number 15 never executed in process DLC 7.4.7.3 Add missing transitions The MSC in Figure 7.62 shows the parts missing in the SDL model to refuse a connection: first, in process dispatch under state waitEstabResp the input of L_ReleaseReq is missing: Figure 7.63 shows this input added, followed by the transmission of DM. Second, when DM is received in dispatch, the answer DM is missing: Figure 7.64 shows this answer added, passing the DM to process DLC. Now, as process DLC can receive DM, the basic block 15 should be covered by the exhaus- tive simulation. Exhaustive Simulation 247 cnx_refused dlca.dispatch inst_1_atob inst_1_btoa dlcb.dispatch dlca/ datalink/ datalink/ dlcb/ dispatch(1) atob(1) btoa(1) dispatch(1) l_estabreq( 0 ) inst_1_dlca.dlc dlca/dlc(1) v76frame( sabme : (.0.) v76frame( sabme : (.0.) ) t320(12.0) I_estabind( 0) waitEstabResp answer waitUA waitUA _releasereq( 0 added v76frame( dm : 0.) ) v76frame( dm (.0.) ) v76frame( dm : (.0.) ) dicstopped( 0 L_ReleaseReq basic block 15 input added _releaseind( 0 ) now covered Figure 7.62 Connection establishment from A refused by B process dispatch(1, 1) Saves waitEstabResp This is a priority input V76frame DLCpeer:= L_EstabResp L_ReleaseReg V7tframe V76para ! SABME ! DLCi (DLCnum) DLCnum = DLCs(DLCpeer) (DLCpeer, False) DLCpeer Null ) ( True ) ( False) DLCs(DLCpeer) L_Establnd L_ReleaseInd := OFFSPRING V76frame (DLCpeer) (DLCpeer) (DM :(. DLCpeer.)) V76fra