Re: Re: Conformist
"Paul Rayner [email protected] [domaindrivendesign]" <[email protected]> Thu, 17 Mar 2016 20:46:12 -0600
| Newsgroups | gmane.comp.programming.domain-driven-design |
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| Message-ID | <CAKKp0qhjgujFQy_VPTb+uCZgxHCkYT+be8zyQafXZKRXL80e=Q@mail.gmail.com> |
--001a113d3a1c5ec90f052e49c226 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable s/that happen/that pattern/ On Thu, Mar 17, 2016 at 8:45 PM, Paul Rayner <[email protected]> wrote: > Tom, > > Conformist is typically conforming to the upstream domain model without > sharing the actual implementation. However, conformist could also include > utilizing the upstream implementation, but purely in a client-only > relationship (not changing the upstream code) and perhaps only making > additive changes. Most teams that start sharing actual code wind up as > shared kernel unless they're really careful, but often without applying t= he > guidelines and warnings that go along with that happen, and get themselve= s > in all kinds of difficulties. > > Paul. > > On Wed, Mar 16, 2016 at 5:03 PM, [email protected] > [domaindrivendesign] <[email protected]> wrote: > >> >> >> Tom, >> >> I agree that there is only little advice on how to implement the concept= s >> of DDD. Most of the samples one can find are way to simple to be a guida= nce >> for the questions arising from real world implementation problems. >> >> Let's for a moment assume that you are right. What are the consequences >> of A directly using entities and domain services of B? How to they alig= n >> with some of the more general goals of software architecture and DDD in >> particular? >> >> >> If A directly references entities of B, the B developers are no longer >> free to change their entities without the risk to break something in A. >> That is not only a compile time problem. Usually A starts piling up >> assumptions on the behavior of the B entities nobody outside of A is awa= re >> of. Changing the behavior of an entity in B could break those assumption= s >> causing bugs in A that are hard to find because they show up much later. >> Choosing this path deliberately could be called =E2=80=9EShared Kernel= =E2=80=9C. Anyway, >> only after some time you will probably call it =E2=80=9EBig Ball Of Mud= =E2=80=9C. >> >> >> The idea of bounded contexts is to divide the whole system into several >> smaller systems by setting up boundaries between them. There are good >> reasons for that explained in the blue book. One that goes for the >> developers: It gives you more freedom to change your stuff within the >> context without raising the risk to break something outside. But you wil= l >> have to respect the boundaries=E2=80=A6 >> >> >> Does that make sense? >> >> >> Rgs, >> >> >> Thomas >> >>=20 >> > > --001a113d3a1c5ec90f052e49c226 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <head> <style type=3D"text/css"> <!-- /* start of attachment style */ .ygrp-photo-title{ clear: both; font-size: smaller; height: 15px; overflow: hidden; text-align: center; width: 75px; } div.ygrp-photo{ background-position: center; background-repeat: no-repeat; background-color: white; border: 1px solid black; height: 62px; width: 62px; } div.photo-title=20 a, div.photo-title a:active, div.photo-title a:hover, div.photo-title a:visited { text-decoration: none;=20 } div.attach-table div.attach-row { clear: both; } div.attach-table div.attach-row div { float: left; /* margin: 2px;*/ } p { clear: both; padding: 15px 0 3px 0; overflow: hidden; } div.ygrp-file { width: 30px; valign: middle; } div.attach-table div.attach-row div div a { text-decoration: none; } div.attach-table div.attach-row div div span { font-weight: normal; } div.ygrp-file-title { font-weight: bold; } /* end of attachment style */ --> </style> </head> <html> <head> <style type=3D"text/css"> <!-- #ygrp-mkp { border: 1px solid #d8d8d8; font-family: Arial; margin: 10px 0; padding: 0 10px; } #ygrp-mkp hr { border: 1px solid #d8d8d8; } #ygrp-mkp #hd { color: #628c2a; font-size: 85%; font-weight: 700; line-height: 122%; margin: 10px 0; } #ygrp-mkp #ads { margin-bottom: 10px; } #ygrp-mkp .ad { padding: 0 0; } #ygrp-mkp .ad p { margin: 0; } #ygrp-mkp .ad a { color: #0000ff; text-decoration: none; } --> </style> </head> <body> <!-- |**|begin egp html banner|**| --> <br><br> <!-- |**|end egp html banner|**| --> <div dir=3D"ltr">s/that happen/that pattern/<div class=3D"gmail_extra"><div= ><div class=3D"gmail_signature"><div dir=3D"ltr"><div class=3D"gmail_signat= ure"><br></div></div></div></div><div class=3D"gmail_quote">On Thu, Mar 17,= 2016 at 8:45 PM, Paul Rayner <span dir=3D"ltr"><<a href=3D"mailto:paul@= virtual-genius.com" target=3D"_blank">[email protected]</a>></span= > wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;bo= rder-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr">Tom,<div><br></= div><div>Conformist is typically conforming to the upstream domain model wi= thout sharing the actual implementation. However, conformist could also inc= lude utilizing the upstream implementation, but purely in a client-only rel= ationship (not changing the upstream code) and perhaps only making additive= changes. Most teams that start sharing actual code wind up as shared kerne= l unless they're really careful, but often without applying the guideli= nes and warnings that go along with that happen, and get themselves in all = kinds of difficulties.=C2=A0</div><div class=3D"gmail_extra"><span class=3D= "HOEnZb"><font color=3D"#888888"><br clear=3D"all"><div><div><div dir=3D"lt= r"><div>Paul.<div><br></div></div></div></div></div></font></span><div><div= class=3D"h5"><div class=3D"gmail_quote">On Wed, Mar 16, 2016 at 5:03 PM, <= a href=3D"mailto:[email protected]" target=3D"_blank">thomasschanko@y= ahoo.com</a> [domaindrivendesign] <span dir=3D"ltr"><<a href=3D"mailto:d= [email protected]" target=3D"_blank">domaindrivendesign@yah= oogroups.com</a>></span> wrote:<br><blockquote class=3D"gmail_quote" sty= le=3D"margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(= 204,204,204);border-left-style:solid;padding-left:1ex"> <u></u> =20 <div style=3D"background-color:rgb(255,255,255)"> <span>=C2=A0</span> <div> <div> <div> =20=20=20=20=20=20 =20=20=20=20=20=20 <p></p><p><span>Tom,</span></p> <p><span>I agree that there is only little advice on how to implement the c= oncepts of DDD. Most of the samples one can find are way to simple to be a = guidance for the questions arising from real world implementation problems.= =C2=A0</span></p> <p><span>Let's for a moment assume that you are right. What are the con= sequences of =C2=A0A directly using entities and domain services of B? How = to they align with some of the more general goals of software architecture = and DDD in particular?</span></p> <p><span></span><br></p> <p><span>If A directly references entities of B, the B developers are no lo= nger free to change their entities without the risk to break something in A= . That is not only a compile time problem. Usually A starts piling up assum= ptions on the behavior of the B entities nobody outside of A is aware of. C= hanging the behavior of an entity in B could break those assumptions causin= g bugs in A that are hard to find because they show up much later. Choosing= this path deliberately could be called =E2=80=9EShared Kernel=E2=80=9C. An= yway, only after some time you will probably call it =E2=80=9EBig Ball Of M= ud=E2=80=9C.</span></p> <p><span></span><br></p> <p><span>The idea of bounded contexts is to divide the whole system into se= veral smaller systems by setting up boundaries between them. There are good= reasons for that explained in the blue book. One that goes for the develop= ers: It gives you more freedom to change your stuff within the context with= out raising the risk to break something outside. But you will have to respe= ct the boundaries=E2=80=A6</span></p> <p><span></span><br></p> <p><span>Does that make sense?</span></p> <p><span></span><br></p> <p><span>Rgs,</span></p> <p><span></span><br></p> <p><span>Thomas</span></p><div><br></div><p></p> </div> =20=20=20=20=20 =20=20=20=20 <div style=3D"color:rgb(255,255,255);min-height:0px"></div> </div> =20=20 </blockquote></div><br></div></div></div></div> </blockquote></div><br></div></div> <!-- |**|begin egp html banner|**| --> <br> <br> <!-- |**|end egp html banner|**| --> <div width=3D"1" style=3D"color: white; clear: both;"/>__._,_.___</div> =20=20=20=20=20=20 =20=20 =20=20=20=20 <div id=3D"fromDMARC" style=3D"clear:both; margin-top: 10px;"> <hr style=3D"height:2px ; border-width:0; color:#E3E3E3; backgroun= d-color:#E3E3E3;"> Posted by: Paul Rayner <[email protected]> <hr= style=3D"height:2px ; border-width:0; color:#E3E3E3; background-color:#E3E= 3E3;"> </div> <!-- Start Recommendations --> <!-- End Recommendations --> <!-- |**|begin egp html banner|**| --> <img src=3D"http://geo.yahoo.com/serv?s=3D97476590/grpId=3D8116923/grpspI= d=3D1705007181/msgId=3D24746/stime=3D1458269214" width=3D"1" height=3D"1"> = <br> <!-- |**|end egp html banner|**| --> =20=20 <!-- |**|begin egp html banner|**| --> <br> =20=20=20 =20=20=20=20=20 =20 <!-- |**|begin egp html banner|**| --> <div id=3D"ygrp-vital" style=3D"background-color: #f2f2f2; font-fam= ily: Verdana; font-size: 10px; margin-bottom: 10px; padding: 10px;"> <span id=3D"vithd" style=3D"font-weight: bold; color: #333; text-tr= ansform: uppercase; "><a href=3D"https://groups.yahoo.com/neo/groups/domain= drivendesign/info;_ylc=3DX3oDMTJlc2FtcTBrBF9TAzk3MzU5NzE0BGdycElkAzgxMTY5Mj= MEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwN2dGwEc2xrA3ZnaHAEc3RpbWUDMTQ1ODI2OTIxMw--"= style=3D"text-decoration: none;">Visit Your Group</a></span> <ul style=3D"list-style-type: none; margin: 0; padding: 0; display: in= line;"> <li style=3D"border-right: 1px solid #000; font-weight: 700; di= splay: inline; padding: 0 5px; margin-left: 0;"> <span class=3D"cat"><a href=3D"https://groups.yahoo.com/neo/groups/do= maindrivendesign/members/all;_ylc=3DX3oDMTJmYWt0cTZmBF9TAzk3MzU5NzE0BGdycEl= kAzgxMTY5MjMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwN2dGwEc2xrA3ZtYnJzBHN0aW1lAzE0NT= gyNjkyMTM-" style=3D"text-decoration: none;">New Members</a></span> <span class=3D"ct" style=3D"color: #ff7900;">1</span> </li> </ul> </div> <div id=3D"ft" style=3D"font-family: Arial; font-size: 11px; margin-top: 5p= x; padding: 0 2px 0 0; clear: both;"> <a href=3D"https://groups.yahoo.com/neo;_ylc=3DX3oDMTJkaDIzZjdtBF9TAzk3ND= c2NTkwBGdycElkAzgxMTY5MjMEZ3Jwc3BJZAMxNzA1MDA3MTgxBHNlYwNmdHIEc2xrA2dmcARzd= GltZQMxNDU4MjY5MjE0" style=3D"float: left;"><img src=3D"http://l.yimg.com/r= u/static/images/yg/img/email/new_logo/logo-groups-137x15.png" height=3D"15"= width=3D"137" alt=3D"Yahoo! 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