A REVZEW ] AS a service to our readers, PER has reached an a g r e e m e n t to reprint reviews of books and papers on simulation and modeling that originally appeared in A C M Computing Reviews. CR is a m o n t h l y jotu-nal that publishes critical reviews on a broad range o f c o m p u t i n g subjects including simulation and modeling. As an ACM m e m ~ r , you can subscribe to CR by writing to ACM H e a d q u a r t e r s . rl I. 6 I. 6.1 I. 6.2 SIMULATION AND MODELING Simulation Theory See ~1,807-05,49[1.6.2| Simulation Languages BAGRODIA, RAJIVE L. (Univ. of California, Angeles); CHANDY, K. M.; AND 8807-0549 M ISR.A,JAYADEV(Univ. of Texas, Austin) A message-based approach to discrete-~vent simulatio¢ IEEE Trans. Softw. Eng. SE-13, 6 (June 1987), 654--665. The authors clearly state their goals as (I) developing a message-based approach to discrete-event simulation, (2) showing that the addition of a small language fragment permits general purpose languages (GPLs) such as FORTRAN and Pascal to join a "class of simulation languages," and (3) giving an example of such a language, MAY, derived from FORTRAN. With the intent of accomplishing these goals, the authors explain the concept of message-based simulation and their design philosophy, note the constraints needed using some examples, and describe an implementation in MAY. This paper is disappointing. Kristen Nygaard (co-developer of SIMULA with O. J. Dahl) once remarked to me that "only the people who used SIMULA for simulation applications really understood the power of the language." In a larger context his criticism was directed more broadly at the softy, are enginering community that rushed to embrace SIMULA as the first language implementing the abstract data Dpe concept while ignoring equally importam characteristics and capabilities. The software engineering community continues to ignore the simulation programming language (SPL) and model representation developments; other-'is°, this paper would not have been published. (3) undefined terminologym'a small programming language fragment" is the crux of the transformation of GPLs to special class SPLs, but a general definition of a fragment is never given. Yet the most serious deficiencies of the paper lie in the ignorance of key issues that supposedly motivate the message-based approach: (1) The authors' entity offer~ nothing beyond the SIMULA process. The generalization of entity to encompass both resources and processes is borrowed directly from the S1MSCRIPT II permanent and temporary entities. (Note that even the terminology is the same.) (2) The wait-until (Boolean) construct has been a subject of discussion for many years [2]. and a justification for not including it in SIMULA is given in a renowned paper [3]. (3) The realization of the "'small programming language fragment" for the example MAY is through a FORTRAN preprocessor. This is a common technique for extending nonextensible languages, which was introduced for simulation applications through GASP in 1963 [4]. Finally, the design philosophy reflects a programmer's explanation of simulation modeling theory. The authors' statement that message-based simulations appear to be more natural for simulating distributed systems remains strictly an opinion in this reviewer's opinion. QR. E. ,Vance. Blacksburg. VA [I] [2] "i'his paper contains (1) conceptual misunderstandings~glMULA does provide message-passing but not in the explicit form preferred by the authors; (2) incorrect statements--a SIMULA object does not cease to exist when no references to it remain if it has not exhausted its operations (see [I ], pp. 48-.49); and [3] [4] BtR'rWlSTLE.G M.: DAHL O.-J.. Mvu~8/d.~. B.: A.~D NVG.4..,,.lU~,. K. SIMUL,I BEGIN. AuerbaclL Philadelphia, 1973. See C,R 12.6 (June 1974). Rev 7.6,834. VAUCHEX..J . G . A "Wait-Until" tlgorithm for general p'ar'p,o,se simulation languages. In Pro<eedin~ of the 1973 Winter Simulatmn Conference (San Francisco. CA. Jan. 1973), spon~red jo4nOv by AIIE, ACM, IEEE, ORSA. SHAKE., SIGSIM, SC3, TIMS. 177-183. NYGx.,dID, K., A.~D DANI_, O.-J. The development of the SIMULA langua$e. In History of Pro~ammin! Lan~'ua~es. R. L Wexelblat (Ed.), Acadern~ Pre~,.I.New York,.., 1981. 439.-.,480. Krvt^r. P.J. GASP--a gent(al aclimty ximulatmn profram. U.S. Steel Applied Re:search Labo~tory, Moaro,eville, PA, 1963. DESIG/,,I. L.A.N.GUAG,E$ GENERAL TF.RMS: Computing Reviews • July 1988 Copyright !987 As%ociadon for Computing Machinery, Inc. Reprinted by permission. PerformanceEvaluationReviewVol. 18 #2, August 1990

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