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employed because PCMEF subsystems support such communication. Acquaintance in the upward direction to objects in neighboring packages can employ interfaces in the acquaintance subsystem to eliminate cycles. Also, acquaintance that in effect spans non-neighboring objects can be channelled through interfaces grouped in the acquaintance package. The PCMEF dependency structure conforms to a number of important architectural principles (Maciaszek and Liong, 2004). Four of these principles are defined below (Maciaszek and Liong, 2003): 1. Downward Dependency Principle (DDP) The DDP states that the main dependency structure is top-down. Objects in higher layers depend on objects in lower layers. Consequently, lower layers are more stable than higher layers. They are difficult to change, but (paradoxically) not necessarily difficult to extend. Interfaces, abstract classes, dominant classes and similar devices should encapsulate stable packages so that they can be extended when needed. 2. Upward Notification Principle (UNP) The UNP promotes low coupling in bottom-up communication between layers. This can be achieved by using asynchronous communication based on event processing. Objects in higher layers act as subscribers (observers) to state changes in lower layers. When an object (publisher) in a lower layer changes its state, it sends notifications to its subscribers. In response, subscribers can communicate with the publisher (now in the downward direction) so that their states are synchronized with the state of the publisher. 3. Neighbor Communication Principle (NCP) The NCP demands that a package can only communicate directly with its neighbor package. This principle ensures that the system does not disintegrate to an incompressible network of intercommunicating objects. To enforce this principle, message passing between nonneighboring objects uses delegation. In more complex scenarios, a special “acquaintance” package can be used to group interfaces to assist in collaboration that engages distant packages. 4. Explicit Association Principle (EAP) The EAP visibly documents permitted message passing between classes. The principle demands that associations are established on all directly collaborating classes. Provided the design conforms to PCMEF, the downward dependencies between classes (as per DDP) command the associations.. Associations resulting from DDP are MANAGING COMPLEXITY OF ENTERPRISE INFORMATION SYSTEMS unidirectional (otherwise they would create circular dependencies). It must be remembered, however, that not all associations between classes are due to message passing. For example, both-directional associations may be needed to implement referential integrity between classes in the entity package. The architectural principles, as those explained above, define (in the holon context) “… a set of fixed, invariant rules, which account for the coherence, stability, and the specific structure and function of its constituent holons.” (Koestler, 1980, p.454). Koestler calls such a set a holon’s canon. The canon is fixed but it leaves room for variable strategies, which determine how rules are actually “implemented” 5 UNIFYING PROACTIVE AND REACTIVE DEPENDENCY MANAGEMENT 35 As stated in Introduction, the supportability of the system must be proactively designed into it as well as reactively monitored and verified. The resulting roundtrip engineering requires the support of a dependency management tool. This Section presents briefly how a dependency measurement tool, called DQ (Design Quantifier), is used for roundtrip engineering with metrics (Maciaszek and Liong, 2003). DQ is designed to analyze a program code and evaluate its conformance to the architectural framework (PCMEF or similar). DQ calculates class, message and event dependency values for each class in a subsystem, the sum of metric values for the subsystem as well as for the whole system. It highlights any nonconformances that it discovers. The nonconformance ranges from offending fields, offending methods to offending classes as governed by the implemented framework. DQ reverse-engineers a program and discovers all object dependencies. Class dependencies represented as associations are easily noticeable both in the system design and in the code. However, implicit dependencies such as acquaintance and local variables of methods are difficult to see. These implicit dependencies are hidden assumptions that may significantly impact the supportability features of a system. Implicit dependencies (typically in message and event dependencies) may introduce new class dependencies that need to be presented to the system designer. DQ performs an architectural conformance analysis (i.e. if the code conforms to the design).
36 ENTERPRISE INFORMATION SYSTEMS VI The tool accepts the PCMEF framework for conformance analysis but it can be easily configured to suit other frameworks. DQ understands and computes various complexity metrics, not discussed here (ref. Maciaszek and Liong, 2003). DQ is configurable for other frameworks provided the definition of the framework is given to it. The information that is required includes the notion of neighboring packages, naming conventions used to identify methods or classes of significance such as event classes, weights of different association links. With these values provided, DQ can calculate the dependency metrics for a system and can produce detail information whether the system conforms to the architecture. DQ supports roundtrip engineering by making the retrieved information available to any visual modeling tool. The tool can be used in visualization environments to provide informative details regarding the system. In particular, DQ can provide a trace of method calls (services) from one class to another and therefore provide an impact analysis on a system when a particular method is called (or modified). Tools like DQ provide useful reactive metrics for a given program and assist in proactive analysis of the program design. They can be used to verify that the system conforms to an architecture framework and if the dependency minimization principles are adhered to. Without a rigorous architectural framework, supported by tools that measure the conformance of the system to the framework, managing a complexity of any large development is infeasible. 6 SUMMARY AND CONCLUSION This paper summarizes fundamental findings of industry-based research conducted by the author over the last decade or so (Maciaszek et al., 1996). The research aims at identifying necessary conditions for building supportable systems. The intellectual background behind the research has been provided by the holon abstraction for interpretation of structures and behaviour of biological systems (Koestler, 1967; Koestler, 1980). To be able to manage complexity of enterprise information systems, we have to be able to measure complexity of system designs (proactively) and programs (reactively). Although not discussed in this paper, the metrics must be able to determine the comparative level of system’s supportability (understandability, maintainability and scalability). Object dependencies, to determine the supportability level, are initially computed from a system design. A proper architectural design, such as the PCMEF design, minimizes the object dependencies for a system. However, the principles of an architectural design can, and frequently are, broken by bad programming practices that allow for indiscriminate communication between objects. Computing dependencies from the code has two main goals. Firstly, we are able to discover programming violations of an architectural design. Secondly, we are able to reverse-engineer all dependencies from code to design models and, in the process, we are able to revise the dependency metrics for the system. The ultimate outcome is, hopefully, a system with supportability characteristics. Measuring supportability of designs and programs cannot be done manually. The paper referred to a tool, called DQ (Design Quantifier), which is able to analyze any Java program, establish its conformance with a chosen supportable architectural framework, compute complete set of dependency metrics, and visualize the computed values in UML class diagrams. REFERENCES GAMMA, E. HELM, R. JOHNSON, R. and VLISSIDES, J. (1995): Design Patterns. Elements of Reusable Object-Oriented Software, Addison-Wesley, 395p. KOESTLER, A. (1967): The Ghost in the Machine, Hutchinson of London, 384p. KOESTLER, A. (1980): Bricks to Babel, Random House, 697p. MACIASZEK, L.A. (2005): Requirements Analysis and System Design, 2 nd ed., Addison-Wesley MACIASZEK, L.A. GETTA, J.R. and BOSDRIESZ, J. (1996): Restraining Complexity in Object System Development - the "AD-HOC" Approach, Proc. 5th Int. Conf. on Information Systems Development ISD’96, Gdansk, Poland, pp.425-435 MACIASZEK, L.A. and LIONG, B.L. (2003): Designing Measurably-Supportable Systems, Advanced Information Technologies for Management, Research Papers No 986, ed. by E. Niedzielska, H. Dudycz, M. Dyczkowski, Wroclaw University of Economics, pp.120-149. MACIASZEK, L.A. and LIONG B.L. (2004): Practical Software Engineering. A Case Study Approach, Addison-Wesley, 829p.
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Page 5 and 6: vi TABLE OF CONTENTS PART 1 - DATAB
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Page 9 and 10: CONFERENCE COMMITTEE Honorary Presi
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Page 13 and 14: Invited Papers
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Page 37 and 38: EVOLUTIONARY PROJECT MANAGEMENT: MU
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RELATIONAL SAMPLING FOR DATA QUALIT
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TOWARDS DESIGN RATIONALES OF SOFTWA
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((Brown et al., 1998), pp. 159-190,
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sive data filtering, presentation (
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• implementation changes in servi
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MEMORY MANAGEMENT FOR LARGE SCALE D
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Data Rate [bytes/sec] 1600000 14000
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E.g., DV Camcorder Camera Packets (
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Procedure CheckOptimal (n rs 1 ...n
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MEMORY MANAGEMENT FOR LARGE SCALE D
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PART 2 Artificial Intelligence and
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110 ENTERPRISE INFORMATION SYSTEMS
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DYNAMIC MULTI-AGENT BASED VARIETY F
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AN EXPERIENCE IN MANAGEMENT OF IMPR
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ANALYSIS AND RE-ENGINEERING OF WEB
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Module p0 Customer Itinerary Send I
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departments: the marketing dept. se
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• An acyclic module M is usable,
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BALANCING STAKEHOLDER’S PREFERENC
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The scenarios will provide an abstr
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BALANCING STAKEHOLDER'S PREFERENCES
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BALANCING STAKEHOLDER'S PREFERENCES
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A POLYMORPHIC CONTEXT FRAME TO SUPP
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A POLYMORPHIC CONTE XT FRAME TO SUP
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FEATURE MATCHING IN MODEL-BASED SOF
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combination of solution domains - a
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• features for all the concepts:
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Existence In both steps it is possi
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matching strategies are maximal, mi
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TOWARDS A META MODEL FOR DESCRIBING
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elementary message (ae-message) can
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problems on a pragmatic level, whic
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TOWARDS A META MODEL FOR DESCRIBING
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INTRUSION DETECTION SYSTEMS USING A
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INTRUSION DETECTION SYSTEMS USING A
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(k� 1) (k) (k�1) (k) p � w
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Table 5: Performance Comparison of
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A USER-CENTERED METHODOLOGY TO GENE
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carries out the second phase of the
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1 1 1 1 2 PROCESS STORE ENTITY EDGE
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constraints rules. KOGGE (Ebert et
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PART 4 Software Agents and Internet
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CABA 2 L A BLISS PREDICTIVE COMPOSI
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y disables evidencing severe mental
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Figure 4: Symbols emission in DAR-H
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they evidence a generalization erro
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A METHODOLOGY FOR INTERFACE DESIGN
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and mobility loss coupled with redu
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Tradeoff: The default input is poss
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Sessions on the VABS which are held
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A CONTACT RECOMMENDER SYSTEM FOR A
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A CONTACT RECOMMENDER SYSTEM FOR A
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- "Going to the sources". The user
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Here are the matrix W and P for our
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EMOTION SYNTHESIS IN VIRTUAL ENVIRO
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theme turns out to be surprisingly
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6 FROM FEATURES TO SYMBOLS 6.1 Face
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sions are described by different em
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Electronic Imaging 2000 Conference
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to the accessibility problem for th
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Figure 3: Hierarchical View of the
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4 CONCLUSIONS AND FUTURE WORK On th
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PERSONALISED RESOURCE DISCOVERY SEA
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profile, the user defines his curre
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Abdelkafi, N. .....................
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