* Lehman, M. M., "The Programming Process", IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969  Home/Search   Document Not in Database   Summary   Related Articles   Check

..... Non linear relationships: An additional challenge in process modelling, prediction, control Other common characteristics of industrial software evolution processes relevant to the present discussion have been identified by a series of empirical investigations over a period of some 30 years [leh69,74,78,85,89], most recently as part of the FEAST 1 and 2 [www01] projects (1996 2001) These studies have assembled evidence supporting the suggestion that such processes tend to display similar behaviours at some level abstraction. Some of these have been encapsulated in statements, termed laws ....

* Lehman, M. M., "The Programming Process", IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969

....on computers, where continuous software process improvement is of major, universal concern. Keywords Best practice, management guidelines, software evolution, software evolution theory. 1. Introduction The software evolution phenomenon [leh01b] was first identified as such in the early 70s [leh69,bel72]. It is reflected in an intrinsic need for continuing maintenance and development of software used to address an application or solve a problem in real world domains. Until recently, however, it did not arouse general interest. This has now changed as demonstrated by events such as IWPSE 2001. ....

....for further improvement. It is increasingly recognised as essential for further systematic control and improvement of the software process [e.g. ben00] 2. Precursor Investigations One of the earliest investigations of software evolution was triggered by a study of the IBM programming process [leh69]. It has been actively pursued ever since. Thirty years of observation and interpretation has produced results that include eight laws of software evolution [e.g. leh74,85,97] the SPE program classification [leh85] a principle of software uncertainty [leh89,90] the FEAST hypothesis ....

* Lehman MM, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY, Sept. 1969.

....of S type systems [13,14] With few exceptions, business and organisational systems are of type E though they may be built from S type elements [7] Thus, the restriction to the latter does not imply a significant loss in generality of what follows. 3 EVOLUTION PHENOMENOLOGY A 1968 study [9] initiated a prolonged investigation of the growth of OS 360 370 and other systems. It led over a period of time to, inter alia, the identification of a series of eight behavioural descriptors that were termed laws of software evolution. The term laws was used because the observed patterns ....

*Lehman MM, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969.

....of Software Evolution Revisited MM Lehman Department of Computing Imperial College London SW7 2BZ tel: 44 (0)171 594 8214 fax: 44 (0)171 594 8215 mml doc.ic. ac.uk Abstract Data obtained during a 1968 study of the software process [leh69] led to an investigation of the evolution of OS 360 [leh85] and and, over a period of twenty years, to formulation of eight Laws of Software Evolution. The FEAST project recently initiated (see sections 4 6 below) is expected to throw additional light on the phenomenology underlying these laws, ....

....improvement to ensure beneficial exploitation of their potential. 1 Historical Background The first three of a total of now eight laws of software evolution 1 were formulated in the mid seventies [leh74] arising from analysis of data first acquired during a study of the IBM programming process [leh69] 2 . These three were discussed in somewhat greater detail in 1978 [leh78] Two further laws were introduced in a 1980 paper [leh80a] with the sixth introduced in a footnote [leh91] The remaining two have been discussed in presentations but are published here for the first time. All relate ....

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* Lehman M M, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969

....it really valid The assertion grew out of ruminations about the importance of orderly and systematic processes as the basis for assuring the quality of products and improving productivity in developing them. Applying the discipline of orderly process to software was not original with me. Lehman [13] and others [18] had suggested this long before. But I was troubled because I had started to see the development of a whole new discipline and technology around the idea of software process, and to notice the emergence of many notions and tools that seemed eerily familiar. I was starting to see ....

M. M. Lehman. The Programming Process. In IBM Res. Rep. RC 2722, IBM Res. Center, Yorktown Heights, NY 10594, Sept. 1969.

....to implement these needs were then developed, initially on an ad hoc basis, and added to, in general, a waterfall [roy70, boe76] type process. And so with other aspects of the software process. The need to understand and improve it was recognised from the beginning of the digital computer age [wil51, ben56, leh69, roy70, boe76]. The discussion at the NATO Software Engineering conferences [nau69] bux70] should also not be overlooked. Wider awareness was triggered by a series of International Process Workshops, the first of which was held in 1984 [spw84] A keynote lecture by Osterweil [ost86,97] and a response to ....

....Institute (SEI) at Carnegie Mellon University. This culminated in their CMM models, related improvement technology and the emergence of an international SPIN (Software Process Improvement Network) movement. 2. The Laws of Software Evolution A 1968 9 study of the IBM programming process [leh69] 3 provided, inter alia, quantitative data on various attributes relating to successive releases of IBM s operating system OS 360 and on the effort expended in going from release to release. As data on further releases became available a series of models reflecting the growth trends of the ....

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* Lehman MM, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969

....systems system dynamics PROCESS MODELLING AND PROGRAMMING The ICSE 97 program committee will not have found it difficult to select Lee Osterweil s classic paper Software Processes are Software Too [1] as the most influential paper of ICSE 87. As evidenced by a number of earlier publications [2, 3, 4, 5] and the first three of the now regular International Process Workshops [6, 7, 8] this paper did not pioneer the concept of process studies and process modelling. But, as predicted, his fresh approach and the underlying philosophy captured and retained the imagination and fascination of individual ....

.... SOFTWARE PROCESS A second major development that signals a change in direction for process modelling arises from the realisation that the software process is a complex, multi loop, multilevel feedback system [11] This was first recognised following a 1969 study of the IBM programming process [3, 12] which led eventually to a study of the evolution of OS 360 and to the conclusion that the system s growth was regulated by a self stabilising feedback process [13] From this it followed that understanding and improving the process required it to be treated as a feedback system [14] Moreover, in ....

Lehman M M, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969. Also. in [13], 39 - 83

....over 25 years ago [bel72, leh78] The FEAST hypothesis (section 6) identifies this attribute and its consequences as the constraint. The laws of software evolution are now understood to be their reflection [leh96c] 2 The Laws of Software Evolution A 1968 9 study of the IBM programming process [leh69] provided, inter alia, quantitative data on various attributes relating to successive releases of IBM s operating system OS 360 and on the effort expended in going from release to release. As data on further releases became available a series of models reflecting the growth trends of the system ....

* Lehman MM, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969

....or mechanism from which the information was derived. The latter constitutes genuine feedback control [oxf81] that includes application and system definition and their operational domain. Evolution of the system and its components is driven, guided and controlled by feedback from many sources [leh69,85]. The regular system dynamics that emerges determines many of the characteristics of 31 5 95, 11:38 am 2 526 CACM[papers] the evolution process [bel72, leh85] In strong contrast, S type processes are, at the highest level, open loop by definition. The specification of an S type program ....

....of feedback in the development of E type software and its role in determining the dynamics of that process has long been recognised. It was referred to in passing by several speakers at the Garmisch Conference [nau69] At about the same time it was briefly discussed in the 1969 Programming Process [leh69] report. The first tangible evidence of an identifiable dynamics of evolution followed some years later [bel72] More detailed studies were reported in subsequent papers [leh80,85] As an example brief mention may be made of the early identification of the feedback stabilised and controlled growth ....

Lehman M M, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969. Also. in [leh85], pp. 39 - 83

....little attention as a research topic, it has long been recognized as a significant factor in software processes. It was, for example, referred to in passing by several people at the software engineering workshop in Garmisch [10] and is also discussed briefly in Lehman s Programming Process report [7]. Sequence No. 0 1000 2000 3000 4000 5000 6000 7000 8000 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Size Figure 1: The Growth of OS 360. Lehman and Belady [1] 9] provide one of the earliest examples of feedback control at work in the evolution of OS 360. Figure 1 depicts the growth of OS 360 in ....

M. M. Lehman. The Programming Process, pages 39--83, 1969. In [9].

....mastering the feedback aspects of the software evolution process, opening up new paths for process modelling and improvement. Keywords: Software: process, evolution, process metrics, dynamics and improvement; Lehman s laws 1 Introduction A 1968 study of the IBM software programming process 1 [leh69,85] led, inter alia, to metric based studies of OS 360 2 [bel72,leh74,85] and other systems [leh80b,kit82] Analysis of data relating ultimately to some 26 of OS 360 releases and sub releases, identified and ordered by their release sequence number rsn [cox66] yielded insights into various ....

....metrics work [fen96,ieee94,kit82,96,vot95] FEAST 1 is believed to exemplify an original metrics based approach to the study of the software process and software evolution. This approach has been consistently followed from the first primitive study of OS 360 in the late sixties and seventies [leh69,85] to the current investigation. The study was triggered by a general observation; the universal and persistent problems accompanying software development and maintenance, i.e. software evolution. Following recognition of the problem as appropriate for research investigation [leh69,85] and ....

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* Lehman MM, The Programming Process, IBM Res. Rep. RC 2722, IBM Res. Centre, Yorktown Heights, NY 10594, Sept. 1969

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