(in chronological order of composition)

1. Structured Modeling, draft research monograph, Western Management Science Institute, UCLA, 197 pages, 1/85. Revised 1/6/86. Requests are no longer being filled.

This originally was intended to be the heart of a book on SM. The topic kept expanding and developing, however, so the monograph was cannibalized and extended as a series of working papers. Some day the pieces may be put back together as a monograph.

2. "An Introduction to Structured Modeling," Management Science, 33:5 (May 1987), pp. 547-588. WMSI Reprint 219. Formerly WMSI Working Paper 338, 6/86 (revised 12/86, 2/87, 5/87, 8/87, 3/88).

This introductory exposition serves as the basic reference for all other papers on SM.

3. "Modeling Approaches and Systems Related to Structured Modeling," WMSI Working Paper 339, 27 pages, drafted 7/86; revised and released 2/87. Needs revision.

This companion paper to the previous one discusses related modeling approaches and systems by other authors. It was intended to elicit comments from the authors referenced.

4. "Integrated Modeling Systems," Computer Science in Economics and Management, 2:1 (1989), pp. 3-15. WMSI Reprint 238. Formerly WMSI Working Paper 343, 11/86 (revised 8/87, 3/88).

This paper discusses the general concept of integrated modeling systems in some detail and then considers how SM supports the different kinds of integration that are identified. Extensive use is made of the notion of a four-level model abstraction hierarchy: model instance, model class, modeling paradigm, and modeling tradition.

5. "The Formal Aspects of Structured Modeling," Operations Research, 37:1 (January-February, 1989), pp. 30-51. WMSI Reprint 234. Formerly WMSI Working Paper 346, 5/87 (revised 9/88, 1/89).

This companion to my 1987 Management Science article motivates and formally presents the definitions of all core concepts of SM, and the definitions of associated concepts and constructs. It also presents pertinent basic theory. A tightly integrated running example illustrates all of the main ideas. It stops short of presenting a language for representing structured models, but provides the foundation for all such languages.

6. "SML: A Model Definition Language for Structured Modeling," WMSI Working Paper 360, 129 pages, 5/88. Revised 11/89, 8/90 (now 137 pages). Not intended for publication.

This paper presents a complete language, SML, built on the core concepts of SM as applied to model definition, both for specific model instances and for classes of models. It also establishes rigorously the relationship between SML and the core concepts of SM. The FW/SM prototype implements SML. This paper is a reference work and not a tutorial; for that, see item 11 below.

7. "Computer-Based Modeling Environments," European Journal of Operational Research, 41:1 (July 1989), pp. 33-43. WMSI Reprint 237. Formerly WMSI Working Paper 363, 12/88.

This paper, a written version of two plenary speeches, says very little about SM but a lot about my views of what future modeling environments should be like. In particular, it discusses five desirable characteristics and three of the main design challenges that need to be surmounted in order to achieve this vision.

8. "Reusing Structured Models via Model Integration," Proceedings of the Twenty-Second Annual Hawaii International Conference on System Sciences, IEEE Computer Society Press, Los Alamitos, CA, pp. 601-611, held in Kailua-Kona, January 3-6, 1989. WMSI Reprint 233. Formerly WMSI Working Paper 362, 8/88 (derived from an earlier Informal Note), the appendices of which contain 3 detailed examples not in the published version. Minor revision (4/92), complete with appendices, reprinted in R. Blanning and D. King (eds.), Current Research in Decision Support Technology, IEEE Computer Society Press, pp. 25-55, July 1992.

This paper begins with a review of reusability and modularity ideas from the software engineering literature, most of which are applicable to the modeling context. Many features of SM support reusability and modularity, and these are noted. The main focus of the paper, however, is on achieving reusability and modularity via the integration of two or more models. A 5-step procedure for SML schema integration is proposed for this purpose. Detailed examples illustrate this procedure, and the pros and cons of SM for reuse are discussed at some length.
Some of this paper's examples are reused and discussed from an alternative viewpoint in R. Krishnan, P. Piela, and A. Westerberg, "Reusing Mathematical Models in ASCEND," in C. Holsapple and A. Whinston (eds.), Recent Developments in Decision Support Systems, Springer-Verlag, Berlin, 1993. One of the examples is the basis for the appendix of A. Andronico, L. Cossa, M. Gagliardi and C. Spera, "An Object Oriented Approach to a Model Management System: Characteristics and Examples" (see Part IIB of this Bibliography). Most of the examples are discussed in detail in M. Gagliardi and C. Spera, "Toward a Formal Theory of Model Integration" (see Part IIB of this Bibliography).

9. "Indexing in Modeling Languages for Mathematical Programming," Management Science, 38:3 (March 1992), pp. 325-344. An earlier version appeared as "A Taxonomy of Indexing Structures for Mathematical Programming Modeling Languages," Proceedings of the Twenty-Third Annual Hawaii International Conference on System Sciences, Vol. III, IEEE Computer Society Press, Los Alamitos, CA, pp. 463-473, held in Kailua-Kona, January 2-5, 1990; WMSI Reprint 241. Additional details appear in the appendices of WMSI Working Paper 371, 180 pages, 11/89 (revised 10/90 and 7/91).

All but the most rudimentary algebraic modeling languages for mathematical programming permit constants, variables, expressions, and constraints to be indexed. Because indexing plays a critical role in the design of translators from modeling languages into optimizer-ready data files, this paper takes a close look at exactly what one means by "indexing", and makes a comparative analysis of modeling languages from this point of view.
A taxonomy is given of the most commonly used kinds of indexing structures, namely those based on sets and relations, together with 25 detailed examples illustrating all categories of this taxonomy. We argue for the presence of certain index-related features in modeling languages, and against others such as so-called value-driven set membership (which is the subject of Laurel Neustadter's thoughtful paper "Value-Driven Sets in Modeling Languages: An Analysis," AGSM, UCLA, 9/89).
All examples are worked in full detail (in the working paper only) in four modeling languages: AMPL, GAMS, LINGO, and SML. The results are used to evaluate these languages in terms of relative expressive power, economy of notation, obedience to certain principles of "good" language design, compatibility with relational database technology, and other criteria. Many or all of the examples also have been worked by other people in other languages.

10. "FW/SM: A Prototype Structured Modeling Environment," Management Science, 37:12 (December 1991), pp. 1513-1538. WMSI Reprint 276. Formerly WMSI Working Paper 377, 35 pages, 5/90 (revised 3/91, 7/91), which contains additional details in its appendix about FW/SM's reference documentation generator.

This paper describes the capabilities of the FW/SM research prototype, and comments on how it contributes toward fulfilling a previously published agenda for the development of a new generation of modeling environments (see the EJOR article). The intended audience is all modeling system designers and evaluators, including those who do not happen to take a structured modeling approach. The 16 features noted at the outset are particularly worthy of consideration by this audience.

11. "The SML Language for Structured Modeling," 2-part paper in Operations Research, 40:1 (January-February, 1992), pp. 38-75. WMSI Reprint 279. This is an extract of WMSI Working Paper 378, 160 pages, 8/90.

This is a tutorial on the principal features of SML, a language for describing structured models formalized in Working Paper 360. SML is described in terms of four "levels" of increasing expressive power. Level 1 is "structural modeling," and is very easy to learn. Level 2 adds everything in SML except indices. Level 3 adds indices, but in away that does not support sparsity. Level 4 adds the features necessary to support sparsity, an aspect of many naturally occurring models.
This paper gives particular attention to the aspects of SML that may be worthy of being adapted and transplanted into other model description languages.
The Operations Research extract was constructed by omitting Sections 2.2, 2.3, 3.2, 3.3, 4.2, 4.3, 5.2, 5.3, and many of the appendices, of Working Paper 378. Part I treats levels 1 and 2, and Part II treats 3 and 4. Anyone who is serious about SML should study the working paper version carefully; those who wish access to the full details of SML must turn to Working Paper 360 (item 6).

12. Neustadter, L., A. Geoffrion, S. Maturana, Y. Tsai and F. Vicuña, "The Design and Implementation of a Prototype Structured Modeling Environment," Annals of Operations Research, 38 (1992), pp. 453-484. (Special volume on Model Management in Operations Research edited by B. Shetty, H. Bhargava, and R. Krishnan.) WMSI Reprint 297. Formerly WMSI Working Paper 380, 38 pages, 11/90 (revised 7/91).

This companion to my 1991 Management Science paper discusses FW/SM from the viewpoint of 4 design principles which, although known in the software engineering community, are particularly significant for modeling environments. We convey the main lessons learned from the 5-year implementation effort.

13. "An Informal Annotated Bibliography on Structured Modeling," WMSI Working Paper 390, 69 pages, most recently revised 5/99.  Previous editions: 11/86, 7/87, 1/88, 8/88, 2/89, 11/89, 8/90, 9/91, 8/92, 2/94, 10/95, 12/96, 8/98.  ITORMS, 1:2 (1996) published the 12/96 edition (archived on their site) and also the latest edition.

This document, whose contents are explained by its title, is updated periodically as a service to the Structured Modeling research community. Only items with substantial Structured Modeling content are included.

14. "Structured Modeling," in S.I. Gass and C.M. Harris (eds.), Encyclopedia of Operations Research and Management Science, Kluwer Academic Publishers, 1996.  Revised 6/99 for publication in the Millenium Edition of this encyclopedia.  On-line here.

This is a compact overview of SM for the general reader.

15. "The Changing Needs of Model Management," slides from a presentation at the ORSA/TIMS National Meeting, Boston, 11 pages, 11/93.

This paper, not written up, is based on another with R. Powers: "20 Years of Strategic Distribution System Design: An Evolutionary Perspective," Interfaces, 25:5 (September-October 1995), 105-127. That paper takes 6 long-term evolutionary perspectives on the title topic, namely evolution of:
(1) logistics as a corporate function
(2) computer/communications technology
(3) algorithms
(4) data development and management tools
(5) model features and software capabilities
(6) how companies actually use distribution system design software.
Each has lessons to teach concerning the design of modeling environments, and these do not seem limited to distribution modeling. Among them are the growing importance of model integration, of devices for managing model complexity, of dealing with the entire modeling life cycle, of model maintenance and extensibility, of paradigm neutrality, and of compatibility with relational database systems.

16. "Structured Modeling: Survey and Future Research Directions," ORSA CSTS Newsletter, 15:1 (Spring, 1994). WMSI Reprint 308.  Formerly WMSI Working Paper 432, 21 pages, 3/94.  Updated 5/20/96 and again 6/99.  ITORMS, 1:3 (1996) published the 5/20/96 edition (archived on their site) and also the latest edition.  On-line here.

Surveys and comments on recent research and research opportunities in structured modeling. Topics: improved modeling languages, approaches to various kinds of model integration, extensions designed for simulation modeling, and three topics falling under implementation strategies and technologies, namely host software, language-directed editors, and language-based customization of specialized application packages.

17. Geoffrion, A. and S. Maturana, "Generating Optimization-Based Decision Support Systems," Proceedings of the Twenty-Eighth Annual Hawaii International Conference on System Sciences, Vol. III, IEEE Computer Society Press, Los Alamitos, CA, pp. 439-448, 1/95.  A PostScript version is here.  Another version was presented (with F. Vicuña as coauthor) at the "Structured Modeling Implementations" session at the INFORMS International Singapore, 6/95.

This paper is drawn largely from item 49 of this Bibliography and also serves as a brief introduction to the project described in item 108 of this Bibliography.  Some of these ideas are used in S. Hamacher, L. Benegas, M. França and C. Lysias, “Sistemas de modelagem aplicados a problemas de distribuição de gás,” 1998 (extended abstract submitted for publication in Proceedings of XXX Sobrapo Meeting).

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