We designated the files conta i n i ng the data that drives the computer-aided processes in Manu facturing as DATA fi les. Every drawing sheet i n t h e fu l l d ra w i ng p a c kage i s e l e c t ro n i ca l l y released as a p lot fi le. These on-l ine files, called DRAWING fi les, are effectively the master draw i ngs, and any local ly generated paper prints are temporary worki ng copies . D RAWING fi l es are i ntended only for human i n terpretation (view ing or plotting) ; they do not have to be inter preted as structured data by other fu nctional process software . DATA fi l es are used for that purpose .
B o t h DATA a n d D RAWI NG fi l e s a re m a d e available through a single u n i fied process avail able anywhere on Digita l 's world-wide i nternal
DECnet network . Data secur i ty is provided i n the software by a n access control l ist of specifi ca l ly a u t horized users i n Man u facturing. A l ist method rather than password control was c ho sen since the VMS system has a l l the capab i l i ties to i m pl e m e n t l i s t c o n t r o l ( i d e n t i fy i n g r e mote u sers) . C o n trol o v e r a ccess to t h e o n l i ne p rod u c t d atabase rema i ns w i t h t h e data managers.
The files are organized aroun d the Part Num ber and Revision N umber of the p hysical object . A complete DATA a n d DRAWING fil e set is pro vided for each revision, thus lead ing to a degree of redundancy between fi les. We original ly con sidered solving this redu ndant-data problem i n
1 3 7
On-line Manufacturing Data Access on tbe VAX RROO Project
the traditional CAD/CAM way by defi n i ng sepa rate u n iversal i nterface fi les and designi ng i nte gra ted da tabases fro m w h i c h a n v needed fi l c could be extracted . To achieve t h e pri mary goa l of m i n i m i z i n g a l l de lays i n product data trans fns . however, we concluded that provi d i ng the process s r ec i fi c . bur red u nd a nt , fi l es needed d i rectly i n Manufactu r i ng was worth the pri c e .
T h i s technique e l i m i nated a l l hand-off dclavs a n d a l l o wed t he a l ready proven processes to operate effi c iently . Of course . the risk was t hat data in the redundant fi lcs could in some way d i verge . The refore . Engi n e e r i n g assu med t h e responsi b i l i ty o f veri fyi ng that t h e data was con sistent between them . Engineering uses spec i a l software t o verify t h a t a l l fi les i n a s e t . some of which come from d i fferen t CAD tools . represen t the identical design object and revision state .
The DATA fi les u t i l i zed arc those the starr-up team i d e n t i fi ed as b e i n g d i re c t l y needed for each man ufacturi ng process . Our i deal target for DATA files was the spec ific data set needed by a " work cel l " of t h e m a n u fa c t u ri n g p l a n t : t h i s rypi caUy i n c ludes bot h a computer resource a nd speci fic people that together rece ive and adapt the generic data to the i m mediate needs of their parti cular p l a nt a n d process . To m i n i m i ze rhc process starr - u p r i m e . e l i m i n a t e q u e u es . and ass i g n respons i b i l i t i es c l e a r l y , M DA a vo i d e d usi ng i n termed i a te data formats. These formats h isrori ca I I y req u i re d prcproccssi n g by s o m e t h i rd p a r r y before rhcy c o u l d be u s e d i n t h e plant. W e expected t h e plants t o adapt t h e DATA fi l es to t h e s r c c i fi c n e e d s of t h e i r own pro cesses. For soph is t i ca ted data consu mers w i t h comp l ex m a n u facturing needs, t he source-data design fi les are a lso i ncl uded w i t h the o n - l i n e data.
The practica l real i ties of the many CAD/CAM processes i n usc first req u i red a smooth ly oper ating fi le-ma nagement process . A large n u mber of fi l es are req u i red to support the b u i l d - a n d test processes for o n e designed object. A typi c a l Digital parr (e .g. , a complex C P U logic module)
i s today completely speci fi ed by ') () to 70 DATA
fi les a nd 3 0 to ') () D RAW I N G fi l e s . W i t h t h a t
many fi l es i nvo lved , a k e y to su ccess for t h i s type of fi le m a nage m e n t i s tota l d a t a a c q u is i tion . Thus the process was made mandatory ( not voluntary ) ; rhat is. it cou ld not depend on some one's rememberi n g to do someth i ng The o n l y w a y to acco m p l i s h c o m p l et e d a t a acq u i s i t i o n
1:) 8
was t o i n tegrate t h e data- manage m e n t process w i t h the CAD too ls t h a t generated the sou rce fi les.
The principal JVI DA i m ple m entation concept was to use the extensive VNIS subd i rectories that ' ' be longed ' ' ro e a c h object a n d rev i s i o n a n d t h e n col lect a ll t h e ap rropriate fi les i n to t h e appropriate d i recto r i es . T h i s tec h n i q u e m a kes p o ss i b l e a u s e r d a t a - a c c ess p r o c e s s b a s e d d i rectly o n t h e VMS system i n which a user can a nswer seve ra l q u est ions a b o u t rhc object or rev i s i o n for w h i c h d a t a i s need ed . M DA t h e n pro vi d es h i m w i t h a d i rectory con ta i n i ng t h e fi les relevant r o t h e requested object o r revision . This d i rectory represe nts t h e b o u n d e d set of data . Within t hat set each DATA and DRAW I NG fi le is " named" so that i t is completely identi fi ed even i f moved later to other manufacturing locat i on s . The fi l e - n a m i n g sch e m e i s a lso not c ryptic so t ha t manufacturing users can speci fy and recogn i ze the particu lar fi lcs they nee d .
An underlying objective of the M DA program
was t o p r ov i d e a n e n v i ro n m e n t i n w h i c h a released data fi l c was perceived as bei n g as sta ble as an approved and re leased paper drawi ng. Whenever a set of DATA and DRAWING fi les for a given revi s i o n of an object arc re leased . that set of data becomes " read -only" and is placed under strict contro l . The engineering gro u p w i l l n o t mod i fy a n y fi le w i t h i n t h e set belongi ng to that revis i o n . and su bse q u e n t revi s i ons of rhat object do not overwrite prior revisions.
MDA a l lows users to pu l l data selectively as it is needed rather t han pus h i ng i r a u tomatica l ly to predetermi ned receivers . 'fhe strategy here i s to d e l i ver not d a t a , b u t a u to m a t i c a l l y genera ted not i fi c a t i o n m e ssages o n D i g i t a l ' s e l ectron i c
VAXmai 1 syste m . The generation of m a i l i s tied
to the design-management functions of the hard ware des ign ers a n d the coord i na to rs for c n g i nccri ng change orders (EC:Os ) . The m a i l mes sages are sent to designated representat ives i n a n y o f t h e m a n ufact u r i n g p l a n ts a ro u n d r h c world r o i n form t h e m t o p u l l whatever data t hey req u i re fro m t h e o n - l i n e syste m . Data users i n M a n u fac t u r i n g arc n o t i fi e d b y a u t o m a t i c mes sages whenever new data is issued or when the s t a tu s of e x i s t i n g d a ta c h a nges . T h i s m e t h o d takes advantage of the exis t i ng V M S Mai l fac i l i t i es for iden t i fy i ng remote users. A user access contro l list has been i m p lemented , and a l l user transactions arc logge d . These techn i q ues con-
Digital Technical journal
firm that new data has been received by users and provide an audit tra i l of who accessed par ticular data in case an error is discovered later. Much of the data provided for the product is i ntended for the specific assembly and test pro cesses implemented by the start-up team . Provi sion of this data is made possible by the close coup l i ng of the Engineering Design and start-up team efforts and the sophistication of the data driven fabrication and test processes . In other words, the designs of high-technology products are now a i med a t specific manufacturing p ro cesses for assembly and test. Except for simple dimensional data, much of this product data can no longe r be " post processed " ( by software means only) onto a different manufacturing pro cess. A major process a l teration m ight requ i re reconvening the start-up team and adapting the design and data for the new process.
Revision Management
Each revision o f a part means that t h a t physica l design object has changed i n some way . I n the MDA process a comp l ete set of DATA and DRAW ING files is provided for every revision; there is no i m p l ied or referenced data . All active rev i sions sti l l being bui lt rem a i n o n l i ne , and subse q u e n t revisions do not overw r ite earl i e r rev i s i o n s . I f t h e s a m e D RA W I N G fi l e a p p l i e s t o different revisions, i t w i l l b e provided w i t h each of those revisions. We were concerned i ni ti a l ly that this simpl ified approach wou l d generate a l a rge n u m ber of red u n d a n t files, p a rt i c u l a rl y D RAW I N G fi l e s . H oweve r , a n a n a l ys i s of t h e c o mp l eted sets s h owed t h a t , w i t h t h e C A D design processes i n use, only 1 0 t o 2 0 percent of the fi les were unchanged from one p hysical revision to the next. Our conclusion now is that having some redundant fi les is a cheap price for the benefit and s i m p l i c i ty of having fu l l data sets. Thus no data set has to reference data fro m another set , a nd old rev i s i o n s c a n b e rea d i ly archived .
The MDA process currently has one significant l i m i tation . U n l i ke the existing p rocedur es for paper drawi ngs , there is no standar d control process for putting a formal revision on a DATA file. On the other hand , i t is not clear that a con trol process is sufficiently valuable in a product environment that is tota l ly data drive n . Trad i tiona l l y , when necessary , a paper d rawing can be changed separate from t he physical revision of the object i tself. That can not cu rrently be
Digital Technical Journal No. 4 Februm:v 1 987
done for DATA files since there are no standard procedures that are equivalently recognized for naming them or for controll i ng revisions. I f the DATA files real ly defi n e the physical product , then an erroneous data fi le defi nes t he wrong physical product . In that case, it can be argued, the right way to sign i fy the change is to update the revision of the object i tself. At the present time, if an i ncorrect DATA file is i ncluded in the released data set, the only unequ ivocal way to correct that problem is to advance the p hysical revision and generate a new set of data .
Within the MDA process, the status of any file is specifically marked . (The mere existence of the fi l e within the process does not i mply any particular status . ) Typ i c a l categories of status a re verifi e d , i ssued , released , and obsolete. A status is i mplemented by using the fi le-owner s h i p capa b i l i ties wit h i n the VMS system . As its name i mpl ies, M DA provides on- l i ne access to a l l needed data and drawi ngs for a n y a n d a l l revisions. However, t he formal status (pre l i m i nary , released , etc) o f e a c h part a n d revision avai lable on l in e is controlled and specified by other existing standard procedures. That status i s confi rmed by M DA but cannot be determ i ned solely from the status information that M DA pro vides on l ine with the data .
The M DA process i s not d i rectly cou pled to the control procedures in Manufacturing, but is l i nked d i rectly w i t h status-set t i n g activities i n Engineering. For exa m p l e , the issued status i s s e t b y a p roced ure run b y the prod uct's E C O