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Topic Title: Poll - Which Linking Convention Do You Use?
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Created On: 19-Apr-2004 02:50
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 19-Apr-2004 02:50
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Paul Miller

Posts: 376
Joined: 2-Oct-2002

Hi,

As bit of a poll - I'm interested to know which linking convention is favoured by DOORS users.

Top - Down Convention: (ie: link direction is from from higher level modules to lower level modules eg: System to Sub-System)

Down - Up Convention: (ie: link direction is from from lower level modules to higher level modules eg: Sub-System to System)

Top - Down is considerered to be intuitive and the terminology such as "Impact" and "Trace" used by the DOORS tool supports this convention.

However, some sites prefer the Down - Up convention as this allows the author of a lower level module to establish links without needing RMC access rights to a higher level module, and/or because the link entity relationships have been depicted in a Down - Up context.

Please reply by indicating either Top-Down or Down-Up , plus any supporting commentary.


-------------------------
Paul Miller
Specification Practices Specialist,
EuroCyber,
Melbourne, Australia.
Mobile: +61 (0)418 135 103
Web Site: http://www.eurocyber.biz
E-mail: miller@eurocyber.biz">pmiller@eurocyber.biz
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 19-Apr-2004 08:35
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Tony Goodman

Posts: 1098
Joined: 12-Sep-2002

We always link from the lower level to the higher level. This is mainly for the reason you mention: you dont need write access to the higher level item. This becomes more important in DOORS 7 as we can now link to baselines.

-------------------------
Tony Goodman
http://www.smartdxl.com
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 19-Apr-2004 12:01
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Roy Bond

Posts: 39
Joined: 25-Mar-2003

We also use the Bottom Up approach - primarily to control user access.

We then modified the formal.dxl file to 'correct' the direction of the Impact and Trace analyses.


Roy Bond
Engine Control and Monitoring Systems
MTU Aero Engines
Munich
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 19-Apr-2004 13:15
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David Rose

Posts: 80
Joined: 10-Oct-2003

We link Down-up as well.

We do this not primarily to easy our tracability. Plus if you look at it in a logical manner, the lower you level document the more specific your requirements are. By linking up we are able to say these 5 sub-requirements satisfy this requirement.

On a different note, do the impact and trace wizards work from the top down? We don't use them very often since we developed our own traceability and impact scripts.

-------------------------
David A. Rose TSgt USAF
NCOIC System Administration
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 19-Apr-2004 16:14
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Douglas Zawacki

Posts: 97
Joined: 14-Aug-2003

Paul,

Niether !

We actually cannot use top-down or bottom-up because of the access rights we have established for the formal modules. This certainly causes some frustration with DXL coding because they have changed directionality on me on more than one occasion (again for access rights).

But if I were to have to choose one, I'd say the most prevalent in our scheme is Top-down.

It's unfortunate that one must have access rights to the source module in order to establish a link. That has been a painful issue when designing the security model.


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 19-Apr-2004 16:42
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Anton Drexler

Posts: 25
Joined: 9-Dec-2003

Douglas,

what, for heavens sake, are the principles you are using for designing your DOORS structure?

From a methodical point of view, creating links from, say, a SW requirements spec to a system requirements spec is as well engineering work as writing the SW reqs themselves. Thus, writing SW reqs and creating links to reference documents is done under the same responsibility and, hence, by the same person (or group). So it's clear that for both parts of the work the same access rights have to be provided.

Maybe you have a totally different approach in the business process you are mapping to DOORS; if yes, I would be highly interested to learn about (if this is not restricted by any security policy).

Regards

Toni Drexler
Consultant for Quality Management and Requirements Management
a.s.drexler@gmx.de
(at the moment, supporting RM at Eurocopter Germany)

PS: At EC, we do bottom-up linking




Edited: 20-Apr-2004 at 12:37 by Anton Drexler
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 19-Apr-2004 21:33
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Louie Landale

Posts: 2070
Joined: 12-Sep-2002

Lower to Upper is clearly superior. That's because it is in fact the lower level spec owner that decides which of her requirements "satisfy" the parent requirement. The parent owner may very well decide which of his requirements must be satisfied by a particular child owner (and thus "Allocate" to that child spec), but the actual link is in control of the child since the actual requirement therein is in control of the child.

Parent specs tend to get locked down before child specs and the "source" of the link owns the link. Thus linking up means you can create links between locked-down parents and not-locked-down children.

If the target of the link "owned" the link then top-down would be superior.

Linking top-down has some interum benefit: the parent "Allocates" to a child. The child spec is initially created with an exact copy of the parents requirements, and the link goes down and means "Drives". The child owner than starts working decomposing such parent requirements, and when a couple new requirements are created she links up and "Satisfies" the parent and in so doing either removes the old parent requirement (and so the Drives link), or removes the link itself.

- Louie

Actually Raytheon has a pretty good scheme: Create a text attribute for each parent called "Link_Parent". Child owners insert the AbsNo of the parent object they WISH to link to in that attribute. Write a DXL that periodically creates such links, erasing all others. Thus, typical users never actually create any links. This is great if you do any archiving/restoring since link recreation is already handled. Also, away DBs can "link" to local parents by simply having a copy and inserting their desired links; and when its restored at the master the create links script auto-links it.
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 20-Apr-2004 00:06
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Paul Miller

Posts: 376
Joined: 2-Oct-2002


I have a preference for the Top-Down approach as this matches the Impact, Trace and other analysis type terminology that DOORS uses.

I guess we don't yet have a problem with authors of lower level child modules being given the necesary access rights to higher level parent modules to establish links. A level of professional trust has to be established when allowing edit access to other people work, there's always the occasional exception, but I've found that most professionals stick to simple rules.

I've also been exposed to sites that use Down-Up - they seem happy with it but problems can occur if there is a sharing of DOORS data between Customers, Prime Contractors and Sub-Contractors.

It would be nice if the linking convention is a configurable property of a DOORS DB or Project so that the context of the Impact, Trace and other analysis functions don't have to be reversed which I have found to cause some depair for new comers.


-------------------------
Paul Miller
Specification Practices Specialist,
EuroCyber,
Melbourne, Australia.
Mobile: +61 (0)418 135 103
Web Site: http://www.eurocyber.biz
E-mail: miller@eurocyber.biz">pmiller@eurocyber.biz
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 20-Apr-2004 09:56
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Peter Seager

Posts: 32
Joined: 10-Feb-2003

We normally use the top down convention. It was in use when I took over as Requirements Manager for the project. As others have said, it needs some trust between engineers, but works and to me is logical. Between updates, we make the Object Text and Heading Read only for the engineers which helps everyone.

I have also inherited the Database Manager job. Here the rules are slightly different. All the projects use top down as their choice except if they have to link into another project. In this case the source module is always within their project. It seems to work without problems, partly I expect, because often the source project has the system spec and this links to a unit spec in the invaded project.

The real trick is to make sure traces flow one way to keep the DXL simple. Down one link, up the next can be done but is harder.

I guess one reason I like Top down is that I started from RTM where links are actually stored in the equivalent of link modules and all these problems go away. With RTM top down is the norm. Scripts are a little harder because you have to take into account the concept of primary and secondary ends to the link but once you get your head round that its more versatile.

Peter Seager
Raytheon Systems Ltd, Harlow

Edited: 20-Apr-2004 at 10:13 by Peter Seager
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 20-Apr-2004 10:30
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Jonathan Marshall

Posts: 27
Joined: 10-Apr-2003

We use Down-Up for essentially the same reasons as described by Louie. We also have a DXL which converts a string attribute, which contains the identifier of the requirement you want to link to, into links.

Jon

-------------------------
Jonathan Marshall
EADS Astrium
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 20-Apr-2004 14:30
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Louie Landale

Posts: 2070
Joined: 12-Sep-2002

The "impact" and "trace" wizards supplied are such trash that I just write my own layout DXL. That pretty much resolves any problem where "trace" means ... well ... whatever it actually means.

- Louie
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 20-Apr-2004 14:34
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Louie Landale

Posts: 2070
Joined: 12-Sep-2002

Just to be argumentative; there ARE organizations that work as follows: the Cognizant engineer (knows about technology such as EMI), under supervision of the book boss (responsible for a particular spec), decomposes the EMI requirements in that spec and dictates the content of the EMI requirements in the lower spec. These requirements are then inserted into that lower spec. The lower level book boss, then, is responsible to organize the requirements and add clarity, but is NOT responsible for enhancing its real content. With this scheme links "should" go down.

But in general I agree with you: the lower spec owner (perhaps supervising the EMI guy) decomposes parent requirements, enhances them, and then links them to the parents they satisfy.

- Louie
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 20-Apr-2004 21:14
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Douglas Zawacki

Posts: 97
Joined: 14-Aug-2003

I agree with to down-up approach. But I did not design our system that we are using today.

Anton,

I can't tell you the specifics of our scheme but I can say that the fact of Telelogic requireing writable access to the source module when establishing a link is one of the things that screwed us.

Writable module access and the ability to create/view links should be mutually exclusive....

The other thing that screwed us up was the fact that our Processes and security are complex (and way to anal sometimes) that instead of buying into the bottom up approach they want top level (access rights) people to establish the links of their sub-ordinates. I do not agree with this logic but I cannot change the world.

I agree with the bottom-up approach for the waterfall style of project managment. Typically, the top level information is more likely to be "Locked down" earlier but we do not adhere to any "waterfall" type of approach. We are trying to support an "iterative approach to software development" Thus, everything at every level could change.

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 21-Apr-2004 10:45
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Peter Seager

Posts: 32
Joined: 10-Feb-2003

I agree with Louie about the impact and trace tools. The Analysis Wizard is the usual starting point for me. Builds the structure quickly and then you can go in and customize the actual attributes you display. Looking forward to Version 7 where you don't destroy all your work by accidently selecting the Views drop-down menu.

Edited: 21-Apr-2004 at 10:58 by Peter Seager
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 23-Apr-2004 11:00
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Paul Tiplady

Posts: 176
Joined: 28-Oct-2003

Well we're still starting out really, but having at least five separate database in three countries on two continents, each separately managed and maintained means we are using both Down - Up and Top - Down.

The Down-Up method is used for traceability from high level requirements through design into implementation (where the links go the other way, of course), and to link test specs to design and requirements. Links are pointing UP the left side of the V-model and BACK across from the right to the left side of the V-model.

The Top-Down method is used where the items under DOORS control are limited to requirements, validation and release schedules (you could think of it as tracing the top slice of the V-model). Because the release schedules come first, everything links into them as target, even though they are controlling what's happening on the right side of the V-model. This is less common, and my last communication with the guys trying this method out indicates they're trying to reverse all their links, without much success yet.

I prefer (and am recommending) Down - Up for all our projects, and writing a script to generate trace info into an RTF file.

-------------------------


Paul dot Tiplady at TRW dot com
TRW Automotive
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 23-Apr-2004 13:32
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Andreas Schwarz

Posts: 3
Joined: 27-Mar-2003

We also use Down-Up for essentially the same reasons. (Access rights)

Andreas Schwarz
AUSTRIAN AEROSPACE

-------------------------
Andreas Schwarz a.schwarz@ieee.org
Austrian Aerospace htp://www.space.at

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 12-May-2004 13:39
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Graham Stradling

Posts: 67
Joined: 19-Sep-2002

We use down->up, as our main route too. It tends to be the normal method of most users.

-------------------------
Graham Stradling,

Alcatel-Lucent.
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 21-Jul-2004 19:05
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Nolita Morgan

Posts: 27
Joined: 27-Dec-2002

Down-up (access rights)

-------------------------
Nolita C. Morgan
Computer Systems Analyst
NEXRAD Radar Operations Center
http://www.roc.noaa.gov/
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 24-Feb-2006 23:02
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Akilah Jones

Posts: 23
Joined: 14-Dec-2005



Edited: 24-Feb-2006 at 23:08 by Akilah Jones
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 24-Feb-2006 23:15
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Akilah Jones

Posts: 23
Joined: 14-Dec-2005

We use the Bottom-Up convention, however we do not have a script to "correct" the direction of the trace and impact analysis. I know, from reading the forum post, that one can modify the "formal.dxl" script to get the correct direction. However, being that everyone is relatively new to DOORS here, no one knows how to properly modify the file. I know that at least Roy Bond has modified the script. But, I would greatly appreciate it ANYONE could post the modified script in a reply to this message. Akilah S. Jones Assoc. Software Engineer Hamilton Sundstrand Power Systems San Diego, CA 858-627-6157 akilah.jones@hs.utc.com
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