The CERN X-Window User Interface Management System (XUIMS) is a modular and highly configurable software development environment allowing the interactive design, prototyping, and production of OSF/Motif Human Computer Interfaces (HCI). Fully compliant with the X11R5 and OSF/Motif industry standards, XUIMS covers complex software areas like the development of schematics, the visualization and on-line interactions with 2D and 3D scientific data, the display of relational database data, and the direct access to CERN SPS and LEP accelerators equipment. The guarantee of consistency across the applications and the encapsulation of complex functionality in re-usable and user-friendly components has also been implemented through the development of home made graphical objects (widgets) and templates. The XUIMS environment is built with commercial software products integrated in the CERN SPS and LEP controls infrastructure with a very limited home-made effort. Productivity and quality have been improved through less coding and better HCI prototyping

Van den Eynden, M

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1XUIMSThe X-Window User Interface Management System at CERNM.Vanden Eynden (E-mail : veym@dxcern.cern.ch)CERN SL Controls GroupEuropean Laboratory for Particle PhysicsCH 1211 Geneva 23, SwitzerlandABSTRACTThe CERN X-Window User Interface ManagementSystem (XUIMS) is a modular and highly configurablesoftware development environment allowing theinteractive design, prototyping, and production ofOSF/Motif Human Computer Interfaces (HCI).  Fullycompliant with the X11R5 and OSF/Motif industrystandards, XUIMS covers complex software areas likethe development of schematics, the visualization andon-line interactions with 2D and 3D scientific data, thedisplay of relational database data, and the direct accessto CERN SPS and LEP accelerators equipment.The guarantee of consistency across the applications andthe encapsulation of complex functionality in re-usableand user-friendly components has also beenimplemented through the development of home madegraphical objects (widgets) and templates.The XUIMS environment is built with commercialsoftware products integrated in the CERN SPS and LEPcontrols infrastructure with a very limited home-madeeffort.Productivity and quality have been improved throughless coding and better HCI prototyping.INTRODUCTIONThe X-Window and OSF/Motif industry standards are inuse since 1992 to produce the Human ComputerInterfaces required for the control of the two CERNlargest particle accelerators : SPS and LEP. Thedecision to base the HCI software activity on industrystandards was made to avoid, as much as possible,vendor-specific developments and to guarantee, thereby,the software investment for a long time [1].  The desireto optimize the production of HCIs led to several marketinvestigations and product evaluations.  In 1994, acommercial User Interface Management System wasselected to become the kernel of the CERN X-WindowUser Interface Management System (XUIMS) [2].X-WINDOW AND OSF/MOTIF The X-Window and OSF/Motif software market hasrapidly evolved during last two years and today offers alarge choice of HCI software developmentenvironments.  One could still consider the developmentof HCIs using only the standard X-Window andOSF/Motif libraires, but if a higher degree of abstractionand reusability is required, or if special features (i.e. 2Dand 3D scientific data visualization) are needed, thenusing a powerful software development environmentbecomes mandatory. The four next sections summarisethe different strategies that can be envisaged for thedevelopement of OSF/Motif interfaces.X-WINDOW AND OSF/MOTIF LIBRARIESThe X-Window and OSF/Motif  libraries (Xlib,XtIntrinsics, and Xm) are intended to be called from a Capplication and contain low level functions for thecreation and manipulation of HCI components (i.e.buttons, labels, lists of elements). Any modification inthe HCI requires a change in the C program (i.e. editing,compilation, and debugging development cycle). Thefinal HCI C code is not understandable by any InterfaceDevelopment Tool (IDT) or User Interface ManagementSystem (UIMS) and has therefore to be maintainedmanually.OSF/MOTIF USER INTERFACE LANGUAGEThe OSF/Motif UIL language is a specificationlanguage for describing the initial state of a userinterface for a Motif application. The specificationdescribes the objects (i.e. menus, form boxes, andbuttons) used in the interface and specifies the functionsto be called when the interface changes state as a resultof user interaction.  The main advantage of UIL is that itis understood by most IDTs and UIMSs. Nevertheless,UIL does not address the dynamic aspects of theinterface (i.e. printing an information message when theuser presses a button) and still requires therecompilation of the UIL file after each modification.2INTERFACE DEVELOPMENT TOOLSStandard  Interface Development Tools (IDT) help thedeveloper to design the layout of the interface through aWhat You See Is What You Get (WYSIWYG) interfaceand to generate the corresponding C code. Theapplication code has then to be inserted into stubs. Themain disadvantage of  the IDT is that he HCI behavior(i.e putting an alarm message on the screen) must stillbe handled by the application code, leading to non-reusable software (see chapter about HCI developmentprinciples).USER INTERFACE MANAGEMENT SYSTEMSUser Interface Management Systems (UIMS) add to theIDT functionality the possibility to design and prototypethe dynamic behavior of the HCI. These tools canusually import UIL files and export UIL, C, or C++ HCIcode. Their ability to address both the static anddynamic aspects of the HCI offers for the first time thepossibility to put in place a real HCI softwaredevelopment lifecycle policy.These considerations led us to buy a commercial UIMSand to enrich it with :• new HCI components such as 2D and 3D graphicswidgets,• additional high level C functions (i.e. routines fordirect SPS and LEP equipment access),• templates for a common style and behaviour withinthe SPS and LEP operational environment.THE XUIMS ARCHITECTUREAs shown in Fig 1, XUIMS is a highly modular andconfigurable environment composed of the followingbuilding blocks :• The XFaceMakerTM UIMS. XFaceMaker[3] has aWYSIWYG editor for the interactive creation ofHCI layouts.  The HCI behavior is specified in theform of procedural scripts in a high-level, C-likeprograming language called FACE. The behaviorcan be tested within the tool using the built-ininterpreter and debugger for the FACE scriptinglanguage. C, C++, and UIL code are generated bythe tool. Additional C libraries can be linked into theUIMS kernel (i.e. libraries for SPS and LEPaccelerator equipment access) in order to extend thebasic functionalities of XFaceMaker. Working HCIsproduced with XFaceMaker can run  on anyworkstation without run-time fees (this is also thecase for the other commercial products used inXUIMS). XFaceMaker also allows the programmerto define templates (composite objects) and to addnew widgets to the standard OSF/Motif widgets set.Fig 1 : The XUIMS Architecture    • The XDrawMakerTM drawing package. XDrawMaker[4] is a drawing editor enhanced by the ability toanimate objects. When used with XFaceMaker,every object becomes a widget that can be includedand manipulated in the HCI. Attributes of objects incomplex schematics (see Fig 2) can be handled asany standard OSF/Motif widget. Almost anyimaginable task can be handled with XDrawMaker.Fig 2 : Schematics of CERN’s intricate particle beam network            built with XDrawMaker.            Courtesy of the CERN SL Transfer Line project team. • The XRTTM 2D, 3D, and Table widgets.  The XRT/2Dwidget can display virtually any type of two-dimensional graph, including barcharts, X-Y plots,pie charts, area graphs, and logarithmic scientificcharts. The XRT/3D widget can contour and zone3D data. Users can dynamically rotate, zoom andscale views. The XRT/table widget allowsdevelopers to display and manipulate tabular data.  XFaceMaker        UIMSXDrawMakerXRT WidgetsXuims WidgetsXuims TemplatesXuims Library  Xuims DB3The XRT widgets were selected for their excellentreal-time performance.  Fig 3 shows Xplore, theCERN off-line scientific data visualization packagebuilt with XUIMS and the XRT/2D widget. • The XUIMS library.  This C libary containsadditional functions used for direct access to the SPSand LEP accelerators equipment, for direct access tothe UNIX file system, for providing on-linehypertext help on the WWW, and for the handling ofHCI components (i.e. flashing widgets, informationmessages, and cursor manipulations). • The XUIMS widgets.  Extending the OSF/Motifwidgets set with XFaceMaker is a trivial exercise.New widgets and their associated code can bedeveloped interactively with the WYSIWYG editorand added to the standard palette afterwards. Thisimportant feature has been used to create additionalwidgets for formatted numeric entries, for fileprinting and screen dumping, and for providing helpon version. • The XUIMS templates.  As shown in Fig 3, atemplate is a model, defined by a pre-designedobject, that can be applied to other objects, calledthe instances of the template, which inherit theattributes defined in the template. A template canalso be a composite object (i.e. a main window withpredefined buttons and actions). Templates are veryuseful to encapsulate high level functionality in areusable way and to enforce consistency across theapplications.    Fig 3 : The CERN Xplore off-line scientific datavisualization. Package built with the XUIMS 2D template.• The XUIMS resources database.  The main purposeof this database is to guarantee a standard behaviorfor all X-Window applications running in the SPSand LEP control room.  Consistency is importantboth between applications and within a singleapplication.  Consistency helps the user transferfamiliar skills to new situations.  The user can applythe knowledge learned from one application toanother application, reducing the amount of learningand subsequent calls (i.e. an operator will easilyrecognize a push-button in an application if allpushbuttons have the same background andforeground colors). A primary XUIMS resourcesdatabase [5] contains low priority definitions ofresource values (i.e. fonts and colors) affecting all X-Window HCIs. If needed, a secondary resourcedatabase containing higher priority resource valuescan be provided by the developer for one given HCI.THE HCI DESIGN WITH XUIMSTHE INTERFACE AND THE APPLICATIONThe fundamental principle of HCI softwaredevelopment is the separation between the applicationand the interface [6].The application can be seen as the set of routines andalgorithms specific to the process or equipment to becontrolled (i.e. routine for switching a vacuum pumpON and OFF). The interface can be seen as a set ofwindows through which the user will interact with theapplication.In terms of reusability, one application code may beinvoked by several interfaces  based on differenttechnologies (i.e. a C library used to control anequipment  could be invoked either from an OSF/Motifoperator interface, or from a C program running on aVT100 terminal).The lack of separation between the application andinterface software layers leads, in most cases to non-reusable software (i.e equipment access code containinglowlevel OSF/Motif library calls). A functionalspecification of the data flows between   the interfaceand the application layers is a mandatory step towardsbetter software reusabiblity and a better developmentlifecycle.  The HCI development lifecycle described inthe next section is a first step in this direction.THE HCI DEVELOPMENT LIFECYCLEAs shown in Figure 4, a typical HCI developmentlifecycle with XUIMS [6][7] can be decomposed asfollows :I. The application concept. This phase, also called theuser requirements phase, is aimed at gatheringquantifiable HCI requirements, identifying the futureusers of the system and drawing the HCI metaphor. 4II. The functional specification.  This phase consists ofthe translation of an application concept (developedby a user) into a functional software specification. Itshould be independent of any particular windowingor graphical system.  The functionality of theapplication and interface layers should be carefullyanalysed as well as the data flowing through thesetwo layers. Experience has shown that this phase isvery often omitted by developers. This situationleads in most cases to the development ofmonolithic, windowing-dependent, non-reusablecode. III. Prototyping the interface.  This exercice is aimed atbuilding a first prototype of the HCI layout with aUIMS. The benefits of this phase are theimprovement of the user requirements and thedetection of inconsistent or contradictoryrequirements. At this stage, no connection between the interfaceand the application is implemented. IV. Designing the application.  This phase consists in theimplementation of the application routines (i.e.database access, algorithms, interlocks, ...) asdefined in phase I. V. Generating the working application.  This phaseconsists in linking together the interface codegenerated by the UIMS and the application code inorder to produce the working application.Fig 4 : The HCI development lifecycle with XUIMSVery often the HCI lifecycle has to be iterative andprototyping should never be ignored. This XUIMS HCIdevelopment lifecycle allows the developer to draw thevisual metaphor through which the user views andmanipulates the system before starting any other codingeffort.CONCLUSIONSXUIMS is operational since September 1994 and is usedby an ever growing community of software engineers.Major rejuvenation projects such as the SPS transfer lineproject and several graphical interfaces for the controlof SPS beam instrumentation and beam transfer havebeen developed with XUIMS.  Off-line softwareprojects like the interface to the SPS and LEP Oraclelogging system have also been developed using theXUIMS graphics capabilities.  The robustness of theend-user applications as well as the openness of theenvironment encourages us to reduce as much aspossible home-made developments and to collaboratewith industry. CERN engineers now spend more time onthe analysis and less time on coding. Unfortunately,providing good HCIs remains a difficult task involvingdetailed technical knowledge (i.e. layering of the X-Window system) and concepts of ergonomics. Buildinga functional specification from user requirements is acrucial phase very often omitted by software developers.By using XUIMS, turning a functional specification intoa working application is now a quicker process.ACKNOWLEDGMENTSMany CERN members contributed to both specificationand implementation of XUIMS. I would like to thanks inparticular P.Ninin from the CERN ST division whohelped in the selection of the commercial products, allmembers of the SL division who contributed to establishthe requirements for the future, and finally Y.Maumaryfor his very good feedback and suggestions.REFERENCES[1] The CERN PS and SL Controls ConsolidationProject      CERN PS and SL Controls Groups      CERN Note PS/91-09 or SL/91-12[2] The CERN SL and ST User Interface Management       System - XUIMS       Software User Manual.  P.Ninin, M.Vanden Eynden       CERN SL Note 94-53 (CO)[3] XFaceMaker User’s Guide V3.0.       Non Standard Logics, FR  Functional Specification   Interface Prototyping   Application     Design      Working         HCI    Interace    Design  Application     Concept      InterfaceCode Generation    ApplicationCode Generation5[4] XDrawMaker - The Animated Drawing Design Toolfor the X Window System.       Non Standard Logics, FR[5] The SL X-Window Migration Project       Resources Management Policy.       M.Tarrant, M.Vanden Eynden       CERN SL Note 93-77 (CO)[6] Software Engineering The PSS-05 Way.       Quality Systems & Software[7] Software Engineering Standards.       C.Mazza, J.Fairclough, B.Melton, D. De Pablo,A.Scheffer, R.Stevens - Prentice Hall XFaceMaker is a trademark of Non Standard Logics, France. XDrawMaker is a trademark of Non Standard Logics, France. XRT/2D, XRT/3D, and XRT/Table are trademarks of KL Group, Inc.

XUIMS: the X-Window User Interface Management System at CERN

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