annotate @ 2:fbd7baf6a61f

added content about sw design; some formating
date Fri, 05 Feb 2010 16:40:51 +0100
parents 9b555c009f19
children aebbe3e76f5e
rev   line source
meillo@2 1 .\".if n .pl 1000i
meillo@0 2 .de XX
meillo@0 3 .pl 1v
meillo@0 4 ..
meillo@0 5 .em XX
meillo@1 6 .\".nr PI 0
meillo@1 7 .\".if t .nr PD .5v
meillo@1 8 .\".if n .nr PD 1v
meillo@0 9 .nr lu 0
meillo@0 10 .de CW
meillo@0 11 .nr PQ \\n(.f
meillo@0 12 .if t .ft CW
meillo@0 13 .ie \\$1 .if n .ul 999
meillo@0 14 .el .if n .ul 1
meillo@0 15 .if t .if !\\$1 \&\\$1\f\\n(PQ\\$2
meillo@0 16 .if n .if \\n(.$=1 \&\\$1
meillo@0 17 .if n .if \\n(.$>1 \&\\$1\c
meillo@0 18 .if n .if \\n(.$>1 \&\\$2
meillo@0 19 ..
meillo@0 20 .ds [. \ [
meillo@0 21 .ds .] ]
meillo@1 22 .\"----------------------------------------
meillo@0 23 .TL
meillo@0 24 Why the Unix Philosophy matters
meillo@0 25 .AU
meillo@0 26 markus schnalke <>
meillo@0 27 .AB
meillo@1 28 .ti \n(.iu
meillo@2 29 This paper discusses the importance of the Unix Philosophy in software design.
meillo@0 30 Today, few software designers are aware of these concepts,
meillo@0 31 and thus most modern software is limited and does not use software leverage.
meillo@0 32 Knowing and following the tenets of the Unix Philosophy makes software more valuable.
meillo@0 33 .AE
meillo@0 34
meillo@2 35 .if t .2C
meillo@2 36
meillo@2 37 .FS
meillo@2 38 .ps -1
meillo@2 39 This paper was prepared for the seminar ``Software Analysis'' at University Ulm.
meillo@2 40 Mentor was professor Schweiggert. 2010-02-05
meillo@2 41 .br
meillo@2 42 You may get this document from my website
meillo@2 43 .CW \s-1
meillo@2 44 .FE
meillo@2 45
meillo@0 46 .NH 1
meillo@0 47 Introduction
meillo@0 48 .LP
meillo@0 49 Building a software is a process from an idea of the purpose of the software
meillo@0 50 to the finished program.
meillo@0 51 No matter \fIhow\fP the process is run, two things are common:
meillo@0 52 the initial idea and the release.
meillo@0 53 But the the process inbetween can be of any shape.
meillo@0 54 The time of release and the maintainance work after the release are ignored here, for the moment.
meillo@1 55 .PP
meillo@0 56 The process of building splits mainly in two parts:
meillo@0 57 the planning of what and how to build, and implementing the plan by writing code.
meillo@0 58 This paper focuses on the planning \(en the design \(en of software.
meillo@0 59 The here discussed ideas may be applied to any development process.
meillo@0 60 Though the Unix Philosphy does recommend how the software development process should look like,
meillo@0 61 this shall not be of matter here.
meillo@0 62 Similar, the question of how to write the code is out of focus.
meillo@1 63 .PP
meillo@1 64 This paper discusses the connection between software design and the Unix Philosphy.
meillo@1 65 Software design is the work between the requirements and the plan of how the internals and externals
meillo@1 66 of the software should look like.
meillo@1 67 However, the term ``Unix Philosophy'' was used but not explained yet.
meillo@1 68 .PP
meillo@1 69 The Unix Philosophy is the essence of how the Unix operating system and its toolchest was designed.
meillo@1 70 It is no limited set of rules, but what people see what is common to typical Unix software.
meillo@1 71 Several people stated their view on the Unix Philosophy.
meillo@1 72 Best known are:
meillo@1 73 .IP \(bu
meillo@1 74 Doug McIlroy's summary: ``Write programs that do one thing and do it well.''
meillo@1 75 .[
meillo@1 76 %A M. D. McIlroy
meillo@1 77 %A E. N. Pinson
meillo@1 78 %A B. A. Taque
meillo@1 79 %T UNIX Time-Sharing System Forward
meillo@1 80 %J The Bell System Technical Journal
meillo@1 81 %D 1978
meillo@1 82 %V 57
meillo@1 83 %N 6
meillo@1 84 %P 1902
meillo@1 85 .]
meillo@1 86 .IP \(bu
meillo@1 87 Mike Gancarz' book ``The UNIX Philosophy''.
meillo@1 88 .[
meillo@1 89 %A Mike Gancarz
meillo@1 90 %T The UNIX Philosophy
meillo@1 91 %D 1995
meillo@1 92 %I Digital Press
meillo@1 93 .]
meillo@1 94 .IP \(bu
meillo@1 95 Eric S. Raymond's book ``The Art of UNIX Programming''.
meillo@1 96 .[
meillo@1 97 %A Eric S. Raymond
meillo@1 98 %T The Art of UNIX Programming
meillo@1 99 %D 2003
meillo@1 100 %I Addison-Wesley
meillo@2 101 %O .CW \s-1
meillo@1 102 .]
meillo@0 103 .LP
meillo@1 104 These different views on the Unix Philosophy have much in common.
meillo@1 105 Especially, the main concepts are seen by all of them.
meillo@1 106 But there are also points on which they differ.
meillo@1 107 This only underlines what the Unix Philosophy is:
meillo@1 108 A retrospective view on the main concepts of Unix software;
meillo@1 109 especially those that were sucessful and unique to Unix.
meillo@1 110 .PP
meillo@1 111 Before we will have a look at concrete concepts,
meillo@1 112 we discuss why software design is important
meillo@1 113 and what problems bad design introduces.
meillo@0 114
meillo@0 115
meillo@0 116 .NH 1
meillo@0 117 Importance of software design
meillo@0 118 .LP
meillo@2 119 Why should we design software at all?
meillo@2 120 It should be general knowledge, that a bad plan is better than no plan.
meillo@2 121 As stated earlier in this document, the process of building a software
meillo@2 122 means going from an idea to a release.
meillo@2 123 The development process tells how to get from the idea to the release.
meillo@2 124 Software design tells how the built software should look like.
meillo@2 125 .PP
meillo@2 126 It is not enough that the released software offers all requested functionality.
meillo@2 127 It is a misbelief that only function matters.
meillo@2 128 Building a software the first time is only a small part of the overall work.
meillo@2 129 The larger part begins when the software is released for the first time
meillo@2 130 \(en maintainance and extending work..
meillo@2 131 This part soon covers more time than the time which was needed to build the software the first time.
meillo@2 132 .\" cf. brooks?
meillo@2 133 .PP
meillo@2 134 The extendability and maitainability of a software highly depends on its design.
meillo@2 135 Good design eases these tasks much.
meillo@2 136 Bad design, in contrast, requires much more effort for maintaining and
meillo@2 137 extending the software.
meillo@2 138 Developers should, for their own best, have maintainability and extendability in mind
meillo@2 139 when they design the software.
meillo@2 140 .PP
meillo@2 141 Users of the software do not care about maintainability and extendability,
meillo@2 142 at least not directly.
meillo@2 143 They care about usability and flexibility.
meillo@2 144 They want the software to directly solve their problems.
meillo@2 145 They want to be able to to use all its functions if they learned a few of them.
meillo@2 146 They want to use the software for similar tasks.
meillo@2 147 Software is successful if users enjoy using it.
meillo@2 148 Good software design can offer great flexibility and usability.
meillo@2 149 .PP
meillo@2 150 Good design matters for developers \fIand\fP for users.
meillo@2 151 Hence both groups should care about good software design.
meillo@2 152 Bad design limits the software in some way.
meillo@2 153 It may still provide all requested function, but it will have worse quality,
meillo@2 154 and thus require more work effort for developers or frustrate users.
meillo@2 155 .PP
meillo@2 156 Good software design is to the implementation like data structures are to algorithms
meillo@2 157 \(en if you get the former right, then you do not need to care about the latter,
meillo@2 158 it will simply go the right way.
meillo@2 159 .\" cf. ??? ``good data, bad algos''
meillo@0 160
meillo@0 161
meillo@0 162
meillo@0 163
meillo@0 164 .NH 1
meillo@0 165 The Unix Philosophy
meillo@0 166
meillo@0 167 .NH 2
meillo@0 168 what it is
meillo@0 169 .LP
meillo@0 170 definitions by McIlroy, Gancarz, ESR (maybe already in the intro)
meillo@0 171 .LP
meillo@0 172 cf. unix tool chain
meillo@0 173 .LP
meillo@0 174 enabler pipe
meillo@0 175
meillo@0 176 .NH 2
meillo@2 177 Architecture
meillo@2 178 .LP
meillo@2 179 the most important design decision.
meillo@2 180
meillo@2 181 the topic here
meillo@2 182
meillo@2 183 .NH 2
meillo@0 184 Interface architecture
meillo@0 185 .LP
meillo@0 186 standalone vs. tool chain
meillo@0 187 .LP
meillo@0 188 software leverage
meillo@0 189 .LP
meillo@0 190 possiblities
meillo@0 191
meillo@0 192 .NH 2
meillo@0 193 Results
meillo@0 194 .LP
meillo@0 195 The unix phil is an answer to the sw design question
meillo@0 196 .LP
meillo@0 197 tool chains empower the uses of sw
meillo@0 198
meillo@0 199 .NH 1
meillo@0 200 Case study: nmh
meillo@0 201
meillo@0 202 .NH 2
meillo@0 203 History
meillo@0 204 .LP
meillo@0 205 MH, nmh.
meillo@0 206 They are old.
meillo@0 207
meillo@0 208 .NH 2
meillo@0 209 Contrasts to similar sw
meillo@0 210 .LP
meillo@0 211 vs. Thunderbird, mutt, mailx, pine
meillo@0 212 .LP
meillo@0 213 flexibility, no redundancy, use the shell
meillo@0 214
meillo@0 215 .NH 2
meillo@0 216 Gains of the design
meillo@0 217 .LP
meillo@0 218
meillo@0 219 .NH 2
meillo@0 220 Problems
meillo@0 221 .LP
meillo@0 222
meillo@0 223 .NH 1
meillo@0 224 Case study: uzbl
meillo@0 225
meillo@0 226 .NH 2
meillo@0 227 History
meillo@0 228 .LP
meillo@0 229 uzbl is young
meillo@0 230
meillo@0 231 .NH 2
meillo@0 232 Contrasts to similar sw
meillo@0 233 .LP
meillo@0 234 like with nmh
meillo@0 235 .LP
meillo@0 236 addons, plugins, modules
meillo@0 237
meillo@0 238 .NH 2
meillo@0 239 Gains of the design
meillo@0 240 .LP
meillo@0 241
meillo@0 242 .NH 2
meillo@0 243 Problems
meillo@0 244 .LP
meillo@0 245 broken web
meillo@0 246
meillo@0 247 .NH 1
meillo@0 248 Final thoughts
meillo@0 249
meillo@0 250 .NH 2
meillo@0 251 Quick summary
meillo@0 252 .LP
meillo@0 253 good design
meillo@0 254 .LP
meillo@0 255 unix phil
meillo@0 256 .LP
meillo@0 257 case studies
meillo@0 258
meillo@0 259 .NH 2
meillo@0 260 Why people should choose
meillo@0 261 .LP
meillo@0 262 Make the right choice!
meillo@0 263
meillo@0 264 .nr PI .5i
meillo@0 265 .rm ]<
meillo@0 266 .de ]<
meillo@0 267 .LP
meillo@0 268 .de FP
meillo@0 269 .IP \\\\$1.
meillo@0 270 \\..
meillo@0 271 .rm FS FE
meillo@0 272 ..
meillo@0 273 .SH
meillo@0 274 References
meillo@0 275 .[
meillo@0 276 $LIST$
meillo@0 277 .]
meillo@0 278 .wh -1p