H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... Hyperindex beam down beam up Figure 1: Stratified hypermedia architecture s 2 D = the source of the link e 2 D = the destination of the link c 2 INI = the activation count of the link t 2 Theta = the time of creation of the link The time axis Theta is discrete and totally ordered, see e.g. [12]. So if we have one link 1 , created at time t, and another link 2 created at time t 0 , it is possible to decide which of these two links has been created first if t 6= t 0 . The links in the hyperindex can be partitioned into a set of static links and a set of dynamic links. The static ....

H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984-996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

....needs will be in two, let al..one five or ten years. Consequently, we need architectures that can enable the exploitation of unforeseen opportunities and meet unpredictable needs. Developing information systems in such rapidly evolving contexts becomes like shooting at a moving target [PW95a, PW94, PW95b] This requires us to look at organisations and their information systems as evolving systems [Pro94] Ideally, these systems should be in a constant state of co evolution. In the past years, IT industry has built up practical experiences with different approaches to, what could be ....

H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

....of the data schema is the set of valid populations at each point in time. If the schema does not evolve in the course of time, then the history of the database takes place within this fixed set of valid populations. How this view needs to be adapted in the case of evolving schemas is discussed in [PW95a] and [PW94] Usually a population of a data schema is modelled as a function: where is the set of (populatable) types defined in and is some domain of instances. The state space of a data schema can then be defined as: where is a predicate that determines whether is a proper population of . ....

....a schema version is within this ORM universe. The notion of having a universe of data schemas, and the data schema of a universe of discourse describing a journey (evolution) through this universe as a sequence of versions has been introduced before in the field of evolving information systems ( PW95a] PW94] Pro94] 14 4.1 Information structure universe We assume the reader has a basic working knowledge of the concepts underlying ORM or ER. A conceptual schema is presumed to consist of a set of types . This set can be divided in three subclasses. The first class is the set of object ....

H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

....to a more application centred approach. The general message of these architecture developments is that IT should empower a business with the means to go out and seek new challenges. Developing component based information systems in such rapidly evolving context is like shooting at a moving target [7 9]. Gaining a good understanding of the business context, and the direction in which it is likely to evolve, will make it easier to align business and IT. In [10, 11] it is also argued that business IT alignment is a continuous process, where business is a driving force and IT an enabling force. ....

H. A. Proper and T. P. van der Weide, "A General Theory for the Evolution of Application Models," Department of Computer Science, University of Queensland, Brisbane, Australia, Technical Report 317 1994.

....requiring the information system to evolve as well. This means that the underlying data schema has to undergo yet another set of transformations to incorporate the new requirements. This observation has led to the development of so called evolving information systems (see e.g. BKKK87, TS92, PW95, OPF94, PW94, HEH 94] 1 1.1 Schema Design Through Transformations To further motivate our view on a schema modelling process as a transformation process, we first take a closer look at the involved transformations. A conceptual schema design process usually starts out with an initial draft ....

....then also derive what a schema version within the universe is. 4.1 CDM Schema Universe The universe of data schemas is built from the extra temporal versions of the schema components as identified in section 2. The notion of a universe in which data schemas evolve has been used before in e.g. PW95, PW94] Formally, the information structure universe is provided by: The base sets, like and , provide the set of all possible relationship types and object types respectively. The functions defining the fabric of the information structure, like and , provide the players for any role that may ....

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995. 23

....such evolutions. Examples of application model elements are the object types and their instantiations . An instantiation of an object type assigns a population to object types. The underlying domain for populating object types is the set . For a more elaborate definition of , please refer to [30] [32] or [31] Such a set of functions is referred to as an application model history. In , each function exclusively describes the evolution of some application domain concept, and is referred to as an (application model) element evolution. The state of affairs of history at some point of time (the ....

....by introducing a disclosure schema, comprising the extra temporal schema, and the meta schema of the used modelling techniques. The disclosure schema will be defined gradually via a number of subschemas (stepwise refinement) In figure 11, the overall meta schema of the evolution theory from [30] [32] is provided. Note that this schema also contains constraints ( and methods ( which are not discussed in this text. ISU Figure 11: The meta schema for the general evolution theory As a first refinement, this schema is augmented with a set of (derivable) relations, enabling a convenient ....

H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

.... in ( 19] 20] PSM can be regarded as a common base for object role 3 modelling techniques like NIAM, FORM, ER ( 11] EER ( 27] and IFO [1] Allthough the introduction of the general theory is a substantial and essential part of this paper, focus is on the introduction of EVORM, contrary to [41] which addresses the general theory itself. 2 Modelling the Evolution of Information Systems In this section we discuss our approach to evolving information systems. We start with a hierarchy of models, which together constitute a complete specification of (a version of) a universe of discourse ....

....2.3 The approach The three ER schemata, and the associated action specifications, as discussed above, correspond to three distinct snapshots of an evolving universe of discourse. Several approaches can be taken to the modelling of this evolution (see for a more elaborate discussion [40] [41]) In this paper, we treat evolution of an application model as a separate concept. We will maintain the evolution of distinct application model elements, thus keeping track of the evolution of individual object types, instances, methods, etc. This has been illustrated in figure 7. Each dotted ....

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

....AM History AM Recording History Figure 10: Application Model Evolution for our example 11 4 Schema Evolution in Evolving Information Systems The framework for update in evolving information systems does not yet take the evolution of schemas into consideration. Nevertheless, in [PW93] PW95] Pro94] a formal discussion of this topic is provided. In this article we will only provide an example of schema evolution. It should be noted, however, that the framework for update is applicable for updates of any part of the application model. An event can be any change of state of the ....

H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

....of this set of acceptable logbooks. The logbook is intended as a structuring mechanism for initial specifications in the context of Snapshot Information Systems as well as Temporal Information Systems ( Sno90] Furthermore, it supports the development of Evolving Information Systems (e.g. [PW95], Tre91] NR89] The history of a UoD may also be described by an application model history, such as introduced in [PW95] In this view, the evolution of a UoD is seen as the evolution of its elements. An element evolution describes the state of the element at each point of time. This dual ....

.... the context of Snapshot Information Systems as well as Temporal Information Systems ( Sno90] Furthermore, it supports the development of Evolving Information Systems (e.g. PW95] Tre91] NR89] The history of a UoD may also be described by an application model history, such as introduced in [PW95]. In this view, the evolution of a UoD is seen as the evolution of its elements. An element evolution describes the state of the element at each point of time. This dual vision on evolving information systems will not be elaborated further in this paper. The organization of the paper is as ....

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H.A. Proper and Th.P. van der Weide. A General Theory for the Evolution of Application Models. IEEE Transactions on Knowledge and Data Engineering, 7(6):984--996, December 1995.

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