THIS OLD HOUSE WITH SAS

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1 THIS OLD HOUSE WITH SAS William H. Crouch Old Dominion University Abstract When asked what tools to bring to the job site, Bob Vila would probably list such items as a saw, a ruler, and hammer. While SAS/AF software FRAME entry would be an unlikely candidate for inclusion, the object oriented methodologies that it supports are ideally suited for the development of a home construction application that demonstrates the versatility of the SAS System. The graphical user interface (QUI) that is inherent in SAS! AF software FRAME entry, provides a natural environment that increases application integration through support for dynamic data exchange (DOE), dynamic link libraries (DLL), and object linking and embedding (OLE). This application utilizes this QUI to explore selected activities related to the construction of a house. Among the activities included are: cost estimation, project scheduling, site selection, and materials management. Introduction This application was developed to address two distinct objectives. The fjrst and foremost objective is to teach how SAS/ AF, and SAS/SCL software can be integrated with other software development tools to create dynamic applications that reinforce object oriented concepts. This application is introduced in a senior level software development class, where SAS is the primary language. The students are all majors in information systems and have completed one semester of COBOL and at least one semester of object-oriented programming with C++. Because this application is introduced in the middle of the course they have also written numerous applications using other components of the SAS system, such as SASISTA ~ SAS/GRAPH, and SASlOR software. With thi~ programming background it is appropriate to explore the methods that can be utilized to share data and functions in a Windows environment. This application introduces dynamic data exchange (DOE), dynamic link libraries (DLL), and several techniques for using object linking and embedding (OLE). Restated, this fllst goal is to teach students SAS as an additional development tool that can be applied to problems that are inherent in a business enterprise. The second objective is to reinforce the statistical concepts that are learned in the introductory quantitative methods and management science courses. As such, this application incorporates regression analysis, project scheduling, material requirements planning, as well as illustrating object-oriented concepts. The incorporation of various statistical techniques in the SAS application requires that the student be proficient at software development and understand the fundamentals of quantitative approaches to decision making. The House Construction Application Although the primary purpose is to demonstrate the utility of the SAS system, a brief introduction to the rational behind the choice of a housing application is given. The house construction application was created for two reasons. First, because of the activities involved in building a house, it permitted the inclusion of the statistical techniques previously outlined. Secondly, and most important in an educational environment, is the fact that numerous students expressed interest in this type of application. This is not particularly surprising when it is noted that the average student taking this class is married, has two children and is thirty years old. Even though they have yet to embark on their chosen career path, they have dreamed of owning, and perhaps even building a house. To transform this dream into a possible reality several critical questions must be addressed. They are: How much will it cost, where should it be located, what material should be used and finally, what are the specific planning and construction activities that are involved and in what order must they be completed. This application which is divided into four major modules provides answers to these questions. Although the SAS program consists of forty-seven FRAME entries, discussion will be primarily focus on those that are related to housing price estimation. The hierarchial relationship between those entries that will be discussed is shows in Figure 1. Each of the FRAME entries is associated with a corresponding SCL program. The SCL programs are comprised of sections labeled INIT, MAIN, and TERM. In addition, most of the SCL programs have additional sections with names that correspond to the push button control objects that are defmed in the FRAME entries. The welcome screen, 462

2 provides a brief overview of the application and the kinds of tasks that are involved. The price determination module will be used to demonstrate data sharing between other Windows packages while exploring regression models, price estimation, and graphic data presentations. Figure 1. House construction application shown in Figure 2, is the first to be displayed and is typical of most of the FRAME entries in this application in that it incorporates imported graphics and has three or more control push buttons. Figure 3. The application selection menu Price Determination Module The price determination module consists of six FRAME entries. The primary function of each is as follows: Figure 2. The welcome screen The "Cancel" push button always issues a cancel command, while the "Help" push button always issues a simple message that is then displayed in a text entty box. The help message varies from FRAME to FRAME, but is always at most a single line of text. The "Continue" or "OK" push button usually initiates the processing and frequently invokes another FRAME entty. In this case selecting the "Continue" button causes the "apps" FRAME entty to appear. As can be seen from Figure 3, this screen serves as the primary menu. Processing proceeds from this application selection screen to one of the four major modules, which will estimate the cost of the house, suggest the location, specify the required materials, or generate a project schedule with the associated charts and diagrams. This a. price - module main menu and control program b. data - determines the source of the input data for the application c. model - generates regression models d. estimate - estimates cost based on regression model for the data selected e. graph - determines options used for graph output f. graph 1 - output graph window The module is invoked when "Price Determination" is selected as the application. To provide greater flexibility this module is designed to accept the input data from three distinctly different sources. The input data can be imported from an external file, read in from an existing SAS data set, or extracted from an Excel spreadsheet. Because of this option the first requirement is to ascertain the source of input data. This information is obtained by presenting the input data screen depicted in Figure 4. This FRAME entty named "data", its supporting HSERVICE entries and the associated SCL program will be used to examine object linking and embedding, dynamic data exchange, and dynamic link libraries. 463

3 two copies are produced. One copy is used by the server and the other is stored in the client. Both of these can be updated and modified. Changes made in one copy are not reflected in the other. The application that initiates any changes determines which copy is modified. If for instance while using SAS FRAME entry, you double click on embedded object originally created by CorelDRA W, the CorelDRA W edit screen would display SAS copy of the data. Any changes made would, in general, impact only that FRAME entry in that SAS application. Figure 4. Input data sources Object Linking and Embedding (OLE) OLE is a Windows communication protocol that enables one application, referred to as the client, to use the services or data of another application, called the server, by placing the necessary data or links in the receiving application's document OLE as such, permits the integration of objects from a wide variety of sources making possible the creation of compound documents. OLE objects can be either linked or embedded. The type of OLE object determines how it is stored and manipulated. A linked object in a compound document contains only a pointer or the dynamic link to the server. The actual data that represents the object remains separated from the client document. This single copy of the data is shared by both applications. The presence of the dynamic link guarantees that any changes made by the server will automatically be reflected the next time the client application is invoked. There are two advantages to this approach. First, it reduces the problems associated with data integrity. There is only one copy of the object, although it could be shared by a multitude of applications. The second advantage is that the size of the client documents will be minimized. The storage requirements for the link are relatively modest when compared to those of the actual object. This is especially true when the object contains graphics. A disadvantage to this approach is that the link information must be maintained. It: for example, the original file containing the object is moved, the link information must be updated. The same problem can occur if the client application is moved to a different workstation or network that does not share the same file structure. Embedded objects contain the actual data in addition to the server information. When an embedded object is created A benefit to using an embedded object is that the links to the original data do not need to be maintained, although links to the server application are required if any future editing is anticipated. The disadvantages to using embedded objects are the increased size of the compound document and the data integrity problems inherent when multiple copies of a file are maintained. In addition to linked and embedded objects SAS also supports static objects. These are typically graphics that are imported from the clipboard. These graphics, while enhancing the appearance of the screen can not be edited. They contain only data and lack information about the application that originally created them. Creating OLE Objects The completed version of the "data" FRAME entry as shown in Figure 4 consists of the nine objects. Table I provides information about these nine objects. Name Object Class Object Type datacap OLE - Paste Special static datalg OLE - Paste Special linked data2g OLE - Insert Object embedded data3g OLE - Read Object same as original external PushButton control sasdata PushButton control Excel PushButton control cancel PushButton control help PushButton control Table 1. "data" FRAME entry objects Figure 5 shows the "data" FRAME entry prior to the inclusion of the OLE objects. As previously stated, Figure 4 is the completed version. In Figure 5 the background color has not been set, to make the regions more visible. 464

4 ~f<: Interactive Systems ~ CJ= J7~C",r;::" CC~CCPC 5Ecu-ycr ~C~_ K\llllll\1'IIJ\'(I',Irf-i{:Mf-I~1 datacap r Special Attributes dialog box shown in Figure 7 to appear. An attribute dialog box similar to this is utilized in creating all OLE objects. The title bar indicates how the object was created. The name entry is used to give the object a name. The type entry is always filled in and is not modifiable. In this case the type is a "Picture", indicating a static object. - The last entry is required and is where the entry name is supplied. This example shows how a simple static entry can be created by using an object from the clipboard '--~~- Figure 5. partially completed source data screen The names that appear in the regions in Figure 5 are for reference pmposes only. The four empty regions will be used to demonstrate several methods of creating OLE objects. The frrst two objects named "datacap" and "datalg" represent paste objects. Creation of all paste objects requires actions in both the server and the client application. In this example the server application is CorelDRA W and the client is SAS. To create the first object the screen title "Select Source ofoata" is created in CorelDRA Wand then copied to the Windows clipboard. At this point the appropriate region labeled "datacap" is selected. From the pop-up menus select first Fill and then OLE - Paste Speeial. The Paste Special dialog box shown in Figure 6 should appear. Figure 6. Paste special dialog box This dialog box displays the name of the file "DATACAP.CDR" and the application "CdrawS" that was used in its creation. To create a static object, Picture is selected as the data type and Paste is selected as the method of inclusion. This would cause the OLE - Paste Figure 7. OLE - paste special attributes dialog box CorelDRA W was also used to create the second paste object, "datalg". Although this object will be linked, the method used to create it is almost exactly the same as the one previously discussed. The steps are as follows: a. create drawing in CorelDRA W b. save the drawing c. copy drawing to clipboard d. create or select desired region e. select Fill and OLE - Paste Special from pop-up menus f. choose Object in Paste Special dialog box (Figure 6) g. select Paste Link as method of linking in Paste Special dialog box (Figure 6) g. enter entry name in OLE - Paste Special Attributes dialog box (Figure 7) For the necessary links to be established correctly, it is critical that the file be given a name prior to copying it to the clipboard. If the steps listed above are followed correctly, the Type field shown on the OLE- Paste Special Attributes dialog box will be "Linked". Unlike the previous object, this linked object can be modified at any point in the future by simply double clicking in this region on the FRAME entry. 465

5 Although the clipboard is required to paste an object, it is not utilized when an object is created by either inserting it from another application or copying it from an existing FRAME entry. When inserting an object the desired region is created or selected. The options Fill and OLE- Insert Object are selected from the pull down menus. An Insert Object dialog box similar to that shown in Figure 8 will appear. The application packages that are listed are those that are currently registered with Windows on your system. Applications are usually registered as part of the installation the data from an existing object. To create an object of this type, select the region and choose Fill and OLE - Read Object from the pop-up menus. The Read Object Attributes dialog box will be displayed. As can be seen in Figure 10, the only entry is the name. The name that is entered must match the name of an existing FRAME entry member. Because of this requirement it is often wise to use Figure 10. OLE- read object dialog box Figure 8. Insert object dialog box process. From the list provided choose the Object Type and select OK. Control will now pass to this application package, allowing the object to be created. Each server application has a slightly different method for inserting the object. CoreIDRA W, for instance has an entry in the File menu to exit the program and return the client. The OLE Insert Object Attributes dialog box will appear. This dialog Figure 9. OLE - insert object attribute dialog box box, as seen in Figure 9 requires only the name of the entry. The last OLE object "data3g" is created by simply reading the fully qualified name. It should be noted that the entry type should be HSERVICE. The previous examples have shown three distinctly different methods for creating OLE objects in SAS FRAME entry programs. Dynamic Data Exchange (DDE) Dynamic data exchange offers an alternative method for transferring data and instruction between two different applications. It is less flexible than OLE, but is still appropriate in many situations. The most common situation is when the server is a Windows spreadsheet or database. Excel is used as the vehicle to demonstrate this technique in the House Construction program. When the "Excel Spreadsheet" option is selected the section labeled Excel: in the SCL program is executed. The actions that are preformed are: a. invoke Excel b. open the required spreadsheet c. use the DDE triplet to create a fileref d. manipulate the data in a data step The actual statements that accomplish these tasks are provided in the following segment. The DDE triplet refers to the three identifiers that are required for the client and the server to communicate. The highest level is the application 466

6 name. In this example that is Excel. The second level is the topic. This is typically the document which contains the infonnation that is to be shared. At the lowest level is the item. In this case that is the rows and columns that serve as the cell addresses. 1* The process should execute asynchronously. *1 options noxwait noxsync; 1* Invokes Excel and opens the spreadsheet x 'd:\msoffice\excel\excel c:\spyder\excel\athouse.xls'; '* Creates fileref for the Excel spreadsheet, and identifies the selected rows and columns. *1 filename indata dde 'Excellc:\spyder\Excel\[athouse.XLS]Sheetl!RI CI :RSOC6'; '* Data step reads in the data *' data sasdata.hslabel (keep= y _name y)abel x_name l-x_names x_laben-x_labeis) sasdata.hsdata (keep= y x l-xs); '*- independent variable array array x (S) 8 xl-xs; '*- independent variable labels./ */./ Note: Only the statements relevant to DDE have been included. Those statements that actually process the data have been omitted. To this point the examples that have been presented demonstrate how SAS has incorporated two very power methods for sharing data. Although the use of DDE and OLE expand the capabilities of the SAS system, an even more powerful tool exists in dynamic link libraries. Dynamic Link Libraries (DLL) Dynamic link libraries represent one of the foundations of the Windows application interface. These libraries are separate files that contain functions that can be called by programs and other DLLs to perfonn most common activities. The Windows system can be though of a collection of these libraries. The tenn dynamic linking refers to the process that Windows uses to link a function call in one module or program to the actual function in the library module. The "data" FRAME entry provides an ideal opportunity to use a DLL. When the "External File" option is selected the name of this file must be ascertained. The most common method of obtaining this type of infonnation is through the use of an Open Files dialog box. A short function has been written in C and stored in a DLL to display the required dialog box and return to SAS the name of the file. Figure I I shows this dialog box when the function is called from the SAS program. infile indata; if _n_ = I then do; input y _name $ y _labei$; do i = 1 to S; input x_name {i} $ x_label {i} $; end; 1* one observation with variable names and labels *1 output sasdata.hslabel; end; input y xl-xs; output sasdata.hsdata; run; Figure 11. Open files dialog box To employ any function that is part of a DLL several attributes must be known. As a minimum the SAS program 467

7 must know the name of the DLL, the name of the function the data type of the variable the function returns, and th~ SASCPLUS, and the name of the function is SASOpenFile. The prototype for SASOpenFile is: For this example, the purpose for calling the function is to determine the path and filename of the file to be used in the pricing models. The relevant statements are provided below: void far PASCAL _export SASOpenFile(cbar * path_name); For SAS system this information is entered into a text file that is read prior to the function call. For this sample program the name of that file is "attrib.tab". filename sascbtbl 'c:\spyder\sas\attrib.tab'; data patbname; /* variable to for the path name */ /* attrib.tab routine minarg= maxarg= callseq= arg I update SASOpenFile I I byaddr stackorder= 12r stackpop= called arch= bit16 module= sascplus; format= $cstr200.; The parameters that are included in the routine statement indicate the name of the function, the minimum number of arguments, the maximum number of arguments, the method used to reference the arguments, the order arguments are placed on the stack, the routine that is responsible for the stack, the architecture the DLL expects, and the name of the DLL. Care must be exercised when entering the function name because C is case sensitive. The second statement in this file provides information about the argument that is passed to the function. In thi.s example the arg statement indicates that the argument is a 200 character string that is null-terminated. The "update" modifier designates that this argument as both input and output This function does not have a separate return value. In addition to the attribute file at least two statements must be included in the SAS program to call functions that are part of DLLs. The first is a filename statement. It is used to associate the reserved fileref SASCBTBL with the file that describes the DLL routine. The second entry required is one of the forms of call module statement. The form of the call module statement that is selected is dependent on the data type of the return value. *1 length pathname $ 200; 1* function is called, passing the pathname variable as an argument */ call module( 'SASOpenFile', patbname); /* the path name is written to a macro variable called path *1 call symput('path', pathname); run', data process; infile "&path"; 1* other statements *1 run; Conclusion This application was developed to serve two purposes. The first was to introduce students to SASI AF software FRAME entry and demonstrate how the use of dynamic data exchange (DDE), object linking and embedding (OLE), and dynamic link libraries (DLL) make the SAS system more versatile. An understanding of SAS FRAME objects, SCL, and the methods outlined here for sharing data and functions with other applications should permit students to develop client'server application using the SAS system that provide the business enterprise with powerful and flexible systems. The second goal was to provide a framework which would allow various quantitative techniques to be explored. Although the modules that address this objective are beyond the scope of this paper, the comments from students who 468

8 have used the application has been very positive.. When students are relieved of the tedium of doing the calculations by hand they indicate that quantitative methods are very useful in the decision making process. In fact, two students have used the House Construction application in actually building a house! Please refer to following references for further information about the topic covered. References SAS Institute Inc. (1994). Microsoft Windows Environment: Changes and Enhancements to the SAS system, Release 6.10, Cary, NC: SAS Institute Inc. SAS Institute Inc. (1994). SAS/AF Software: FRAME Entry, Usage and Reference, Version 6, First Edition, Cary, NC: SAS Institute Inc. SAS Institute Inc. (1994). SAS Technical Support TS-322, Accessing External DLLs from the SAS System, Cary, NC: SAS Institute Inc. SAS Institute Inc. (1994). SAS Technical Support TS-325, The SAS System and DDE, Cary, NC: SAS Institute Inc. SAS Institute Inc. (1994). SAS Technical Support TS-460, Accessing External DLLs with SAS 6.1xfor Win32s, Cary, NC: SAS Institute Inc. SAS, SAS/AF, SAS/GRAPH, SAS/OR, SAS/SCL and SAs/STAT are registered trademarks or trademarks of SAS Institute Inc. in the USA and other countries. indicates USA registration. CorelDRA W is a trademark of Corel Corporation. OLE is a trademark of Microsoft Corporation. 469