Pronunciation: di me'tr. The stress is on e, which is pronounced like e in equal.
Answers: There are many answers depending on your point of view. What is new? ====================================================== An important concept of Demeter is to split software into at least two parts: The first part defines the objects. The second part defines the operations. The goal of Demeter is to maintain a loose coupling between the objects and the operations, so that one can make modifications to either without serious impact on the other. This cuts down significantly on maintenance time. The most exciting and novel aspect of the Demeter technology is the concept of adaptive software based on traversal strategy graphs (strategies, for short). When you describe a traversal in a shorter form than writing it out completely, it is called a succinct subgraph specification. Strategies introduce a novel way of loosely coupling software artifacts to make evolution much easier. Strategies are very important since they appear in many aspects of object-oriented software development and other processes: groups of collaborating classes traversing objects e.g., navigation in UML/OCL www.ccs.neu.edu/research/demeter/course/f97/lectures/powerpoint/ file lec9.ppt www.ccs.neu.edu/research/demeter/course/f97/lectures/postscript/ files lec9*.ps defining collections and iterators for Generic Programming (see DJ tool) http://www.ccs.neu.edu/research/demeter/DJ/ transporting objects copying objects marshalling objects parameterizing classes collecting resources queries in data bases expressing views defining participants of collaborations connecting components structure-shy knowledge representation structure-shy planning etc. The programs described above are adaptive programs of dimension 2 since there are two parts. We also consider adaptive programs of dimension n: Adaptive programs are specified by n complementary, collaborating parts, each one addressing a different concern of the application. Those programs are now called aspect-oriented programs. Adaptive programming is the special case of aspect-oriented programming where graphs and strategies are utilized. The main goal of adaptive programming is to separate concerns by minimizing dependencies between the complementary parts, so that a large class of modifications in one part has a minimum impact on the other parts. The complementary parts approach has the advantage that programs become less tangled, more flexible, understandable, and shorter, without loss of run-time efficiency. One or more of the dimensions must be expressed using strategies for the program to be called adaptive. A condensed list of applications of adaptiveness sorted by technique to achieve adaptiveness. Law of Demeter ============== The Law of Demeter was developed early during the Demeter project by Ian Holland et al. and it provided the motivation for the work on Adaptive Programming. We called it "Law of Demeter" because we discovered it while working on Demeter but it is a general style rule for structure-shy programming. Design Pattern Support ===================================================================== Demeter/Java provides excellent support for working with design patterns. Traversal strategy graphs (strategies, for short) are useful for capturing groups of collaborating classes which are involved in a design pattern. Demeter/Java provides outstanding support for an improved form of the visitor design pattern. Behavior is expressed in terms of strategies and visitors which are loosely coupled to each other and to the class diagram. What is the most general definition of Adaptive Programming (AP) ================================================================ Adaptive Programming is the special case of Aspect-Oriented Programming where at least one of the aspects is expressible in terms of graphs and where the other aspects or components refer to the graphs using strategies. In summary, AP is about adapting to changes in a graph and about succinct specifications to achieve the adaptation. begin definition An adaptive program consists of n parts a1,a2, ... ,an, where each part ai expresses a concern expressed in language Ai. There is a combination function c which maps the n parts to an executable program c(a1,a2, ... ,an). In an adaptive program there must exist a graph-based concern, say A1, such that for a "large family" of changes S to elements of A1, the result of the combination function adapts to the change: c(S(a1), a2, ... ,an) ~= c(a1, a2, ... ,an) (adaptability cond.) ~= means that the two programs have "analogous", but different input-output behavior. In AP, the adaptiveness is achieved by using the following mechanism: Elements of A1 are mathematical structures consisting of sets and relations. At least one of the concerns, say A2, is expressed in terms of succinct specifications of a structure related to A1. A specification is succinct if it is "much shorter" than the structure it specifies. end of definition Example: n=2 Split program into two parts: behavior and class graph (e.g., a UML class diagram). Behavior _adapts_ to many changes in class graph. Behavior and class graph concern are connected by strategies, i.e., succinct subgraph or succinct pathset specifications. http://www.ccs.neu.edu/research/demeter/biblio/strategies.html Solves following problem: Many maintenance and evolution tasks for object-oriented programs become simpler and even partially automated. Method ===================================================================== The Demeter Method is a software design and development method for deriving object-oriented software from informal specifications, such as use cases and scenarios. The software is not described directly at the object-oriented level, but at the adaptive object-oriented level with the double benefit that the software gets both shorter and considerably more flexible. The software is called adaptive since it adjusts automatically to a large number of context changes. For other context changes it is easily adaptable by manual intervention. Interface ===================================================================== Demeter provides a high-level interface to your favorite object-oriented programming system. It defines a high-level interface for defining the structure of your classes and objects through class dictionaries. It also defines a high-level interface for defining the behavior of your objects through adaptive programs. When an application is written using adaptive programming, it is much easier to port to a new programming system, like going from C++ to Java. Book ===================================================================== Entitled ``Adaptive Object-Oriented Software: The Demeter Method with Propagation Patterns'', the book introduces the important concepts of adaptive software, such as class dictionaries, and propagation patterns. It presents a simple process model on how to develop adaptive software. The book is written for advanced undergraduate students, graduate students and professionals. The publisher is PWS Publishing Company. Framework Technology ===================================================================== Adaptive Plug-and-Play Components for Evolutionary Software Development is an OOPSLA '98 paper that makes the connection between frameworks and AP. The APPC style of programming can be viewed as programming with many little frameworks. Modeling Behavior with Personalities shows how to improve framework technology using the Laws of personalities. Research group ===================================================================== The developers of the Demeter technology. Demeter Research Group. Some easily accessible publications are: Karl J. Lieberherr, Ignacio Silva-Lepe and Cun Xiao, ``Adaptive Object-Oriented Programming using Graph-Based Customization'', Communications of the ACM, May 1994, pages 94-101. ftp://ftp.ccs.neu.edu/pub/research/demeter/documents/papers/LSLX93-adaptive-programming.ps Ignacio Silva-Lepe, Walter Huersch and Greg Sullivan, ``A Demeter/C++ Report'', C++ Report, SIGS Publications, February 1994. ftp://ftp.ccs.neu.edu/pub/research/demeter/documents/papers/SLHS94-demeter-cpp-report.ps To learn more, see WWW address: http://www.ccs.neu.edu/research/demeter Tools ===================================================================== The tools are distributed free of charge on the WWW in source (and object) form for Demeter/Java, Demeter/C++, Demeter/Perl5 and Demeter/CLOS. Users are very enthusiastic: From Bell Laboratories: "Demeter appears far superior to the methodologies for C++-driving front-end CASE that we've seen from IDE (Software Through Pictures) & Cadre." From Drexel University: "Extremely valuable --- I predict it will sweep the industry" Read more feedback on adaptive software technology. Information about how to get the Demeter Tools/C++ through the Internet is at: ftp://ftp.ccs.neu.edu/pub/people/lieber/DemeterTools.txt Information about how to get the Java Tools Demeter/Java and DJ is at: www.ccs.neu.edu/research/demeter Agriculture ===================================================================== The Greek goddess of Agrigulture. The Demeter project was named after Demeter because we were working on a hardware description language Zeus and we were looking for a tool to simplify the implementation of Zeus. We were looking for a tool name related to Zeus and we chose a sister of Zeus: Demeter. Later we promoted the idea that Demeter-style software development is about growing software as opposed to building software. We introduced the concept of a growth plan which is basically as sequence of more and more complex UML class diagrams. Growth plans are useful for building systems incrementally.
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