MacNews: An Interactive News Retrieval Service for
Contents
1. File Edit Article Query Mas OOOO SSN mets date date 2 01 L 05 11 89 1301 79 lines unread The American woman who walks through the gate to a peasants g i cottage in Poland looks calm and cheerful dressed as if she were ae heading off to a Mets game 2 05 11 89 0236 300 lines unread Editors Here is a list of stories that have moved Wednesday May 10 and through 2 30am Thursday May 11 on The New York Times News Service The list goes backward to 9 a m EST Included is story number priority code category code and keyword 3 05 10 89 2327 82 lines unread CINCINNATI Pete Rose as he has to do for so much of this season could only sit and agonize The Mets using just three hits and a long running comedy of errors by the Reds scored six E unearned runs in the sixth inning Wednesday on the way to an 11 4 jii Figure 3 1 A Processed Query 30 2 1 As the system is receiving the article a status box displays the number of lines in the article and the number received so far When this completes an article window is opened and activated as seen in Figure 3 2 At this point the user may read the article print the article search for some partic ular text or save the article The user can also request other articles up to a total of six or process another query before deciding to exit MacNews 3 2 Performance The MacNews system has relatively good performa2. also accessible with the eR keystroke of the menu is enabled To read an article the user clicks the mouse on the summary of interest and executes the Read option When the article is received the next group of the Article menu functions become active The menu options include Close accessed with the Macintosh standard keystroke aW or the window s close box Save As 16 xS Print oP and Find oF which allows the user to do text searches in the article window The final set of commands are dynamically added deactivated and deleted They allow a user to go directly to a particular article window by taking the menu option or typing ban where n is the number of the article window For example if article windows one and two exist the user can go between them using the menu or typing p lt 1 or p42 or as usual if the window is partially visible click the mouse on some portion of the window If article window one is then closed the bal and respective menu item are disabled Then when article window two is closed the menu is rebuilt and the options to go to a specific window no longer appear on the menu and since no article windows are open the Close Print Save As and Find options are disabled If on the other hand another article was read before article two was closed the menu will be rebuilt containing the ability to access and manipulate the open article window one Therefore the user is always only able to execute com
3. if the program as MacNews does contains scroll bars the programmer is forced to violate abstraction barriers in order to get the scroll bar and text to work together properly Also the scroll bar must created with coordinates that make it fit into a particular window instead of the availability of some high level routine that request a vertical scroll bar fifteen pixels wide to be created for some window Additionally the programmer must indicate that the scroll bar cannot be typed into otherwise the Macintosh software will blindly insert text as if the area under the scroll bar was visible Also once a program decides to use text windows it cannot display multiple fonts or font styles in the same window The lack of a more powerful text manager is a drawback in creating applications that need to implement a graphical display of text items The Macintosh Event Manager provides a powerful way to handle differ ent actions a program needs to execute as explained in Sections 2 2 1 and 2 2 2 However the currently running program also receives events that are intended for other programs Thus a program must always check if the event just received occurred in a window it is managing A true multi user system would automatically issue events to the correct program This would elimi nate a number of problems that the programmer of an application is forced to consider 2 3 3 Serial Driver The Macintosh serial driver provides three basic proce
4. This type of dialog is preferred because it is important that the user know what happened The final type of dialog the modal dialog is used for such things as setting the modem options and getting search criteria There is a need for an additional notification system which is not provided by the Macintosh System a way to display information which is important but not time sensitive For example when the total number of matches in the system has been determined or all the summaries have been received the user should also be informed of the situation However the information is not as urgent as the fact that a connection couldn t be established because the modem was not on But placing this information in a simple dialog means that it will disappear possibly without the user ever reading the message And if the modal dialog or alert mechanism is used the user must respond to the message before continuing even if it may be of little importance to 18 them at the time The Macintosh tends to place messages of this type in an alert dialog with an icon indicating that it is a note rather than something of warning or caution status The approach has two flaws it is unclear that a user in most cases notices which icon is presented in the alert and the user is still forced to respond with a return or clicking the mouse in the alert window It would have been possible to implement a message buffer window that would perhaps have
5. loop divides the process of establishing a connection into smaller more manageable tasks Thus when a user requests that a query be sent the modem loop first accomplishes all the necessary supporting tasks When a request is received the modem loop determines based upon the current connection state if it is possible to handle the request immediately or not If it is not possible the modem loop does the next possible step and reposts the original request The modem loop uses the message segment of the main event loop triggering event to determine what the user is requesting An example will help explain the interaction Assume the user is ready to process their first query When the user selects the menu option Ask the event loop triggers on a menu event The menu event calls a procedure that prepares the query for processing adding appropriate terms and posts a modem event with the message Query Upon receiving the request the modem loop checks its current state and determines 20 that it is in a beginning state and the only task it could complete next would be to open the serial drivers and reset the modem It also determines that it could dial the phone next and that would bring it closer to completing the Query request So it posts two modem events one to dial the phone and one to process the query When the Dial event is received it is completed and the modem loop returns Then when the Query message is received again the same pro
6. not be added The summary window unlike the query window does have a scroll bar as it is expected that it will contain more text than can be visible at any one time Finally the article windows up to a maximum of six are created after the user requests an article All the article windows are effectively identical excepi that they are slightly offset from each other and that they are called by a different number An article window is a standard Macintosh text window complete with title bar scroll bars and a close box The user may also copy text from the article window to other windows or modify the article by using a word processor such as MacWrite The article windows also do not have grow boxes though their implementation is not hindered by the current program The designs of the original program included complex text manipulation that would have prevented the use of grow boxes See Section 4 1 for additional information 15 2 1 2 Menus MacNews includes five basic menus They are from left to right the Apple menu the File menu the Article menu and the Query menu The Apple menu contains all the installed Desk Accessories and an About MacNews option It is standard Apple practice to have the desk accessories and information about your program as options in the Apple menu and Mac News maintains this practice The file menu contains three items Options Page Setup and Quit The Options item allows the user to set the
7. to the scroll bar located in the window The exists field is set when the window represented by the structure is created and is unset when the window is destroyed The type field is set to indicate whether the window that is represented is an ar ticle window query window or summary window Finally the linesInFolder represents the number of lines of text in the window and is needed to do Mac intosh text manipulations The main desire behind having all these items in a single structure was to maintain a location where information about the window could be kept altogether The addition of the exists and type field allow the same structure to be used for a variety of different windows Addi tionally space for the structure only occupies only 26 bytes until the various elements such as the text handle are created at which point space in the heap is allocated to store the contents of the handle The only other data structure used in the implementation of MacNews is a structure to keep track of summaries Summaries are stored as an array of pointers to the structure shown in Figure 2 3 This is done so that only a minimal amount of space is consumed until the summaries are received The summary number is simply the array element number The startPos and endPos indicate the starting and ending positions of the summary text in the summary window This permits the program to determine which summary the user is requesting Siuce the text of the summary wi
8. IS project is extremely valuable as a system with a broadcast channel and a duplex modem connection that can be used as a backup mechanism Gifford87a 4 2 Conclusions On a whole the MacNews implementation was successful It has provided many questions that will require future research but it has given us an idea of what the Macintosh can provide in the way of enhanced user interface for information systems MacNews manages to avoid many of the problems that are associated with other systems Some of these such as the remote process ing are handled by the BCIS framework However several other problems were avoided in the design of MacNews by including full menu or keystroke 35 control keeping the user informed and providing full local processing of information in article or summary units Although the current Macintosh Operating System 6 0 2 is not ideal for communications there is reason to believe that the interface will be greatly improved under System 7 0 Under the features of the new system it is apparent that the Macintosh would provide an even more powerful base for information system interfaces As hoped the work of MacNews has provided an invaluable experience in programming the Macintosh that should ease any transitions of future BCIS systems Finally it is apparent that despite some flaws in design the Macintosh Operating System provides a mechanism for the effective implementation f a sophisticated information ser
9. MacNews An Interactive News Retrieval Service for the Macintosh by David Andrew Segal Submitted to the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degree of Bachelor of Science at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY May 1989 David Andrew Segal 1989 The author hereby grants to MIT permission to reproduce and to distribute copies of this thesis document in whole or in part Signature of Author Department of Department of Electrical Engineering w Computer Science 19 May 1989 Certified bym A David K Gifford Associate Professor of Computer Science Thesis Supervisor Accepted by Ene Leonard A Gould Chairman Departmental Committee on Undergraduate Thesis ARCHIVES users INSTITUTE JUN 16 1989 USRARIAS MacNews An Interactive News Retrieval Service for the Macintosh by David Andrew Segal Submitted to the Department of Department of Electrical Engineering and Computer Science on 19 May 1989 in partial fulfillment of the requirements for the degree of Bachelor of Science in Department of Electrical Engineering and Computer Science Abstract MacNews is a news retrieval program for the Apple Macintosh computer The program using a standard modem connects with the Boston Community Information System BCIS project database to provide the user with news articles of interest MacNews meets the demands of a standard Macintosh inte
10. ammer cannot create a file with a name of type char without causing the system to crash at some later point The programmer is forced to use type Str255 which is then required to be cast to other types when the programmer wants to use a C string manipulation library procedure The problem also occurs for other types that are declared in Pascal but not in C Matters are exacerbated when the programmer uses strict type checking The equivalence of C and Pascal types by the type checker does not equate into equivalence of the types for the procedure calls Finally there appears to be inconsistency in the Macintosh Toolbox con ventions For example to insert text in a window one must send a pointer to ASCIT text as an argument with a separate argument indicating the length of the string To get text that is in the window however one sends a handle as an argument And if one wants to display text in a dialog window the argument is a Pascal string a string with the first byte containing the length of the string 2 3 2 The Managers The Macintosh window dialog and event managers combined with a Re source Editor provide an excellent basis for setting up an application 25 The most basic manger any application uses is the window manager On top of the window manager is the text manager that handles most of the tasks about maintaining text in windows For example to insert some text one simply calls the Toolbox routine TEInsert However
11. cess applies the next step in the connection process gets accomplished and if necessary an additional step in the connection process that must be done to ultimately fulfill the Query request is posted to the event queue and the original Query request gets reposted This continues until the modem loop determines it can send the query Additionally after sending the query the modem loop posts an event that checks on the receipt of information about the number of matches and summary text At any point when a failure is detected the modem state is returned to the highest level possible and ail outstanding events are flushed from the queue Thus if the program is unable to open the serial driver it cleans up whatever it accomplished notifies the user of the error and marks the modem as being in the beginning state If on the other hand the text of the article is received in the wrong order the program flushes the buffers notifies the user and returns to a state where it is waiting for the user to request an article If however the server crashes while receiving an article the modem can be returned to the beginning state and the user is notified that the connection was lost The program only posts the next event as opposed to the next n events needed to complete a task because the Macintosh System Event Queue is of finite size it only holds twenty events and it throws away events that overflow the available space Since the communicat
12. ck is reset every time a character is read 33 Chapter 4 Summary This chapter discusses the areas of future research and enhancement that should be added to improve the MacNews program The second section includes the preliminary conclusions and evaluation of MacNews 4 1 Future Research There are several items that should be improved in the MacNews program First the user s request should be parsed locally for syntax Currently when the user asks a query the server machine determines if an error occurred This however means that not only must a connection be made if one doesn t already exist but the feedback to the user is simply The query did not parse properly as opposed to a more descriptive message such as Missing left parenthesis Additionally an ability to hang up the modem at anytime or cancel the current processing should be added to the system to improve its usability Secondly MacNews should take better advantage of the Macintosh graph ics display Currently only the font is chosen to be news like But the system should perhaps present more of an article texture by providing columns and headlines The original MacNews design called for columns This however led to several conceptual errors that must be researched more fully The first problem was how to decide when to hyphenate words across columns This 34 problem is a well known and difficult research goal Next if the program presents an artic
13. d MacNews Our expe rience with MacNews supports our hypothesis that the Macintosh Operating System is a suitable environment for information systems 1 1 Boston Community Information System The Boston Community Information System BCIS project was designed to explore new information system technologies The system consists of a large distributed database containing information received from the New York Times and Associated Press news wires and several different news re trieval client programs By using one of the client programs and a powerful query language Segal86 users are able to conduct full text searches on the entire database When a user submits a query the BCIS system responds with the number of items in the database that matched the query and a summary for each matching item The summary consists of the date of the article and the first line of text which for news articles tends to be a good indication of the article s contents A user can request the full text of an item by selecting its summary Currently BCIS consists of a polychannel system running on IBM PCs Gifford88 Segal86 an electronic mail program Gifford87c and a UNIX network based program Gifford8S7b MacNews was the first attempt to implement a BCIS client program using the Macintosh environment 1 2 Other Information Systems Information systems can generally be divided into three classes e Those that are dumb terminal interfaces into the i
14. dles the management of all the system dialog windows e macnews c the main module of the program Calls all preliminary set up procedures and then runs the main event loop as discussed previously e menus c manages and creates the program s menus e print c handles the printing of articles and management of the printer driver e serial c completely controls the serial connections including the mo dem loop management e windows c manages all the MacNews windows Then there are three modules which contain specific knowledge about parts of the MacNews purpose These modules are article c summary c and query c They control the obvious specifics of MacNews s operation 24 2 3 Macintosh Support One of the main reasons the Macintosh was chosen for the implementation of MacNews was because of its environment This section describes what support the Macintosh Toolbox provided for MacNews along with some crit icisms about the Macintosh programming environment 2 3 1 Pascal vs C The Macintosh Toolbox was fully implemented in Pascal yet MacNews was implemented in C While in most cases the compiler provided the mechanism for conversion there were still occasions where the programmer was forced to consider the Macintosh Toolbox language For example in the Pascal used to implement the Toolbox all strings are of type String 255 which the THINK C user s manual properly equates with type char in C However a progr
15. dures SerGetBuf which returns the number of characters in the buffer FSRead which reads characters from the buffer and FSWrite which writes characters This ab straction is fine if the number of characters needed to be read is known or whenever there is a character it can be read However if the program wishes to read the input up to a certain character leaving the rest of the input buffer alone it is forced to read the data a character at a time While for 1200 baud communications this is not a problem it is a potential problem as much faster communications become more available Additionally there is 26 no mechanism to have the Macintosh release the processor to other programs until a character is on the line and return to the correct segment of code ie there aren t true process swaps on the Macintosh that would permit better asynchronous communications management 2 3 4 Documentation A major problem with the Macintosh is lack of good documentation and of program examples Apple Corporation provides a set of reference manuals called Inside Macintosh Apple85 but these are not always complete accu rate or free from contradictions For example the documentation for TEClik the procedure that one calls to handle mouse clicks in text windows does not state that the procedure checks the event queue for a double mouse click So if a programmer decides to implement their own meaning for a double click they will get inconsistent beha
16. e Computer in Apple87 Secondly it was hoped that a user familiar with some other program of the Boston Community Information System such as Walter Gifford87b or the PC Program Segal86 would be able to make an easy transition to the Macintosh program To meet the latter of these requirements the concept of a separate query window summary window and article windows remained To meet the first requirement the standard Apple keystroke equivalents were used and all transactions can be done through the menu And as an example of an idea that was not affected by either requirement multiple article windows were implemented MacNews also had the following rather straight forward functional re quirements 11 e allow the user to formulate a query e connect to the BCIS server e communicate the query with the server program e retrieve summaries of the items that match the user s query e retrieve the full articles as requested by the user e allow user manipulation of the articles such as the ability to save print and search the articles Finally in order to simplify future code maintenance and to allow for portability to future Macintosh systems there was a desire for all the code to be written in C MacNews was completely implemented in THINK Cor poration s LightSpeed C 1 6 Organization of the Thesis The remainder of this thesis is organized as follows e Chapter Two presents the design of MacNews along with a discussion
17. e polychannel IBM PC version of the Boston Community Information System was implemented in 1984 The technology available at the time did 10 not permit extensive use of graphics or other user friendly enhancements While the users of the system found that it provided an valuable service they overwhelmingly indicated the need for a better interface Gifford87a The users s suggestions included better keystroke commands the ability to use a mouse stronger control to save files longer query lines better menu facilities searching ability and the use of windows Gifford87a Thus the BCIS Project already perceived to be valuable in its struc ture and content seemed an ideal system to implement changes to test the hypothesis that the Macintosh computer provides a powerful base for im plementing information systems Additionally BCIS provided a framework that would to allow a program to properly split the processing of a user s requests between the host and local machines thereby avoiding some of the speed problems of other systems MacNews uses a standard modem connected to the computer to connect to the BCIS server machine It was hoped that MacNews would implement an improved interface to the BCIS Project 1 5 Specifications The design of the MacNews user interface had two basic requirements The first was to bring the BCIS project into the Macintosh world This included being careful to stay within the guidelines set forth by Appl
18. er has crashed It is possible however that the time out will occur when the system is especially 31 File Edit Article Query pS Article Window mats dal type NYT Copyright 1989 The New York Times aa priority Urgent data 05 10 89 2327EDT CAtEgOry Sports 1 g subject BC METS REDS The Arng title METS OVERCOME BUMBLING FUMBLING REDS WITH 11 4 cottage ij WIN heading a JOE SEXTON 2 ol CINCINNATI Pete Rosa as he has to do for so much of this Editors season could only sit and agonize The Mets using just three hits through and a long running comedy of errors by the Reds scored six Service unearned runs in the sixth inning Wednesday on the vay to an 11 4 tory at Riverfront Stadium The Reds with infielders throwing the ball into the outfield and pitchers throving it into dugouts and against the backstop committed three errors and a wild pitch as the Mets chugged and o chuckled their vay around the bases They sent 11 players to the plate and had move than half of them cross it With one out and runners on first and second the Cincinnati and a tor shortstop Barry Larkin heaved Ron Darling s sure double play arned grounder into right field allowing Keith Hernandez to score Figure 3 2 The Received Article 32 slow To prevent this from occurring the time outs have been chosen to be long enough for most server delays and the ne out clo
19. essing summaries the idle cursor is used The MacNews idle cursor however has hands that advance as the seconds pass to assure the user that something is actually being executed The ask cursor is displayed anytime MacNews is waiting for information about the number of matched articles and finally the receive cursor is displayed while the program is receiving article text While these different cursors have no functional value they do provide additional feedback to the user Another mechanism that provides feedback to the user are dialog win dows There are three types of dialogs those that simply display messages and require no user action to disappear dialogs those that display messages but require the user to hit the return key or click the mouse in its window to disappear alerts and those that the user selects a button to cause some action modal dialogs When MacNews wishes to notify the user of changes in a process that changes state often the plain dialog is used For example while a connection to the server is being established or the lines of article text are being received the state of the process is displayed in a narrow di alog window When the particular process has completed that is either the connection is established or the article received the dialog and its message disappear When the program needs to notify the user of some situation such as the connection being unable to be established the alert dialog is used
20. he Query and Summary Windows 14 The query and summary window are separate windows but they act as a single window in some respects That is they are activated separately a user is working in either one or the other window but they move in a single plane This effectively allows the user to limit the scope of understanding to two different types of windows a processing set of windows the query and summary and article windows The query window is the small window located at the top right hand corner of the screen lts title bar contains the program name and a close box that allows the user to close the window Using the close box on the query window causes the program to exit It does not contain a grow box so it s size is fixed Nor does it contain a scroll bar as the maximum length query fully fits within the fixed window size The user is able to fully manipulate text within this window This includes the ability to paste text that the user copied from the other system windows The summary window is directly below the query window Users may copy text from the buffer but they cannot modify the contents of the window The window does not include a title bar or close box The absence of these tools is not problematic since the query and summary window act together in the processing set The summary window also does not contain a grow box though in the current implementation there are no reasons why one could
21. ion speed is slow in com parison with the Macintosh speed the cost of having to repost the Query request numerous times is minimal This implementation of the connection process allows the tasks required to establish the connection to be divided into manageable pieces It also allows the computer to respond to the user in between doing the various steps of processing a query Additionally this design allows for better control over errors and an understanding of the actual modem state that the program must return to when it encounters a particular error Perhaps the most 21 important benefit of the design is that it allows for a top level understanding of establishing a connection without needing to concern oneself with the actual underlying details of completing each step of the connection 2 2 3 Data Structures MacNews actually needs to store a minimal amount of information in data structures Most of the data received is plain text displayed in a window without concern to its actual contents Thus there are only two MacNews data structures one for window structures and one for summaries The structure for a window contains seven fields which are shown in Fig ure 2 2 The WindowRecord and WindowPtr types contain the information necessary to do most manipulations on Macintosh windows The TEHandle is a pointer to a pointer called a handle and of C type char of the text contained in the window and the ControlHandle is a handle
22. le with two columns side by side it important that the user not have to page to continue one column and then page back to finish the article This however leads to questions of what happens if the user would shrink the screen size or scroll down three lines This problem and original intent to include columns was the reason that the article grow boxes were not included in MacNews Finally the latency of determining the layout of the screen should not be so large that the user will loose interest Another problem was in making MacNews Multifinder compatible The only documentation available on making an application Multifinder avail able that the author was able to locate is only available to registered Apple Developers Additionally there is uncertainty as to whether the energy ex pended in providing better Multifinder compatibility will be wasted when the much awaited Macintosh System 7 0 is released System 7 0 is expected to provide true multi tasking which would seem to indicate the demise of Multifinder In any case the syster w undoubtedly have to be modi fied to provide proper compatibility with the Macintosh multiple application software whatever that turns out to be Finally MacNews should really be expanded to be a polychannel system As discussed in Section 2 3 3 it is unclear if such a system is possible under current Macintosh software due to the inability to have true process swaps However it is clear that the BC
23. lls the appropriate procedures to act upon the user or system request When there is no pending event the Macintosh system posts a NULL 19 event which simply causes the loop to be executed with no action needed to be taken A Macintosh event has several segments the type segment which is used as the trigger and a message segment that contains some additional information about the event that occurred For example if the user clicks the mouse the type of the event is a mouse down and the message contains information on where and when the mouse was clicked Since the event loop is executed regularly certain maintenance procedures are also called every time through the loop MacNews calls the following pro cedures in its event loop A cursor maintenance procedure which checks the position of the cursor to see if it should be the text or arrow cursor A menu maintenance procedure which checks if any changes in the state of the program require the menu options to change A text idle procedure which idles the text cursor in the active text window And the SystemTask proce dure which allows the Macintosh to perform whatever system maintenance tasks it needs to accomplish including updating the desk accessory alarm clock After the initial set up procedures are run the program is completely controlled from the event loop 2 2 2 Modem Loop The modem connection protocol of MacNews is completely managed by a modem loop procedure The modem
24. mands that logically make sense to execute Finally the Query menu contains two options Ask lt A and New rN Ask processes the query currently in the query window and New clears the query and summary windows leaving any articles in windows alone 2 1 3 Keeping the User Informed Apple provides several methods to notify the user of different events occurring during the program s execution The first of these dynamic menus is used by MacNews as discussed in the preceding section The others are the use of dialogs and the ability to change the cursor A user can determine the state of the program by which cursor is dis played The standard Macintosh cursor is the arrow cursor that points to different objects However anyone that has used a Macintosh is also familiar with the watch or idle cursor indicating that the machine is busy Thus the user is able to be kept informed of the machine s state by which cursor is displayed MacNews implements five cursors the standard arrow cursor the idle cursor and ask cursor a text cursor and a receive cursor The arrow cursor is the default When a user moves into an active text window the cursor changes to the text cursor The text cursor makes it easier for the user to distinguish 17 which character position the cursor is truly on so that the user s movements can be more controlled When MacNews is executing a procedure that takes a long time such as waiting for a connection or proc
25. n an eye pleasing manner the generation of the various screens seems to take much too long much greater than just modem delays for a user to endure The program does not seem to do prefetching of the material so that if the user wants to view a following page they must wait for the material to be received over the communications link Additionally when an action is occurring a WORKING box is placed in the upper right hand corner of the screen and the keyboard is locked but the user is not really informed as to what is going on Finally the search ability of the program is limited to specific preset phrases that restrict the freedom of the user The LEXIS NEXIS system is a general information retrieval sys tem that contains many different databases including court decisions law review articles and the articles from several different newspapers and news wires It uses a query language that allows a user to search in a particular database eg the New York Times database and find matches anywhere in the text The ability to search in this manner is extremely powerful How ever the screen presentation is extremely basic It does not take advantage of graphics menus or mouses The system also forces a user to remember dot commands commands that consist of a followed by several letters when they are not using the special terminals which have special action keys ie a SIGN OFF key Another problem with this system i
26. nce On average it takes thirty five seconds to connect to the host all of the delay caused by the latency of the modem Summaries are received about every two seconds each summary is on average four lines and 320 characters Once again the delay appears to stem entirely from the modem sneed I am unsure how the program will handle faster modems and whether code will have to be optimized to use them efficiently Right now over 90 of the modem loop time is spent in wait loops that advance the cursor hand allow for system tasks and check if a character has arrived The discussion in section 2 3 3 presents the manner in which the Macintosh serial driver abstractions may impede on future speed ups in communications 3 3 Robustness MacNews appears to interact marginally well with other programs Undoubt edly it will have to be enhanced to be more Multifinder compatible if the Macintosh does not expand to true multi tasking See Section 4 1 The program seems to be robust in the handling of communication errors It determines with fairly good accuracy what type of error occurred and what recovery is necessary from resetting the server to resetting the connection Additionally all the modem transactions have time outs while waiting for a response This seems to adequately handle the cases where the connection terminates during any of the transactions It also prevents the program from completely hanging waiting for a character when the serv
27. ndow is static as 22 struct NewsWindowRecord int exists int type WindowRecord wRec WindowPtr wPtr TEHandle TEH ControlHandle vScroll int linesInFolder F3 Figure 2 2 The Window Data Structure discussed in Section 2 1 1 the character position never changes The status field indicates whether the summary is read unread or in an article window This allows the program to provide better information to a user For example if the user requests to read an article already in a window the program can easily go to the window containing the article Finally the lines field holds the number of lines contained in the article the summary represents This is used to insure that all the lines of text are actually received when a user wishes to read a particular article Both of these data structures arose from the design considerations of MacNews and seemed to simplify the implementation of the program 2 2 4 Modularity This section describes how the code for MacNews was organized into sepa rate files or modules The modularity of the program allowed for each code segment to be tested separately It also allows for future changes to be more easily implemented The central modules have functional value They are as follows 23 struct SummaryRecord long startPos long endPos int status int lines Figure 2 3 The Summary Data Structure e cursors c handles cursor set up and maintenance e dialogs c han
28. nformation database ie the user runs their own modem program to connect to the server machine Examples of services in this class are CompuServe The Source and Dow Jones News Retrieval e Those that provide the user interface on the personal computer but do all the processing at the host The LEXIS NEXIS system is an example of this type of service e In the final class are systems that provide both a user interface and processing power on the personal computer MacNews the BCIS PC program Prodigy and AppleLink are included in this group of services The Prodigy AppleLink and LEXIS NEXIS information sys tems are explored more fully below Prodigy is an interactive personal service program that runs on the IBM or compatible line of computers with a graphics monitor and modem The user is able to see the latest news read stories get stock information purchase items and play games The program s various screens contain graphics intended to make the presentation more accessible to a large group of users The various actions are selected by moving the cursor to various boxes l Prodigy is a service mark of Prodigy Services Company a partnership of IBM and Sears AppleLink is a trademark of Apple Computer Company LEXIS and NEXIS are trademarks of Mead Data Systems containing action phrases and then hitting return While the program does present a large number of information sources i
29. of the support provided by the Macintosh Toolbox e Chapter Three presents the actual operation of the program and a brief discussion on the performance of the program and its fault tolerance e Chapter Four discusses the conclusions that have been observed in light of preliminary experimental evidence and areas for future research and enuancement 12 Chapter 2 System Design This chapter describes the design of the user interface and program structure of MacNews The user interface conforms with the Macintosh guidelines Apple87 and the program structure is modular to allow for future changes or upgrades 2 1 User Interface The main goals of the user interface was that it be stream lined easy to use and conform to the Macintosh guidelines while allowing a user of other BCIS programs to easily adapt to the Macintosh version The design is presented in three sections the program s windows the design of the menus and the notification system The user interface is an adaption of many ideas for a window version of BCIS including some preliminary design notes for X Walter a version of one of the BCIS programs that would run under the X Window System Segal87 2 1 1 Windows MacNews has three basic window types a query window a summary win dow and article windows When a user starts MacNews both the query and summary windows are placed on the screen See Figure 2 1 13 File Edit 8riicie Query Figure 2 1 T
30. one or two lines of the last messages much the way EMACS keeps a one line buffer with the last message remaining at the bottom of the screen until another message replaces it However this did not seem to be standard in the Macintosh system For lack of a better solution messages of the aforementioned type are currently implemented as note alerts which as discussed forces the user to respond This may make the program more annoying to use especially for the experienced user The dialogs and cursors combine to keep information flowing to the user Therefore it is hoped that the user does not imagine that the computer has crashed when there is a long operation running 2 2 Program Structure This section describes the implementation or code organization of MacNews First the main two control sections of the code the event and modem loops are discussed Then the data structures used are justified And finally the modular organization of the code is presented 2 2 1 Event Loop Macintosh applications are all built upon an event driven system The Mac News system is likewise built around a main event loop Events of all types such as keyboard actions mouse clicks and disk inserted events are posted to the Operating System Event Queue Every time through the loop a call to the Macintosh Event Manager inquires about whether an event is waiting in the queue Then the loop determines what type of event it has received and ca
31. rface while maintaining continuity with the other programs of the BCIS project The design and implementation of MacNews is presented It is our conclusion based on preliminary results that the Macintosh Operating System does provide a good environment for information systems Thesis Supervisor David K Gifford Title Associate Professor of Computer Science Acknowledgments I would like to thank Professor David K Gifford for providing a freshman with the opportunity to work in his research grcup In my three and a half years with the Programming Systems Research Group I have learned a great deal not only about computer science but also about myself I would also like to thank several members of the lab who have provided immeasurable help with both my courses and the development and comple tion of this thesis At various times they provided suggestions answers and criticisms Robert G C t James William O Toole Jr Ricardo R Jenez and Mark A Sheldon all have my deepest gratitude Finally to whom this thesis really belongs my mother and the memory of my father Two persons without whom I obviously would not be here and to whom I owe everything I am Contents 1 Introduction 1 1 Boston Community Information System 1 2 Other Information Systems o LS Callar Seas oy we ce Be Ae pig oe ee Sd ELE Motivations rs eaaa ES a Bald a 1 5 Specifications wb e cana la Ae eee GD OS 1 6 Organi
32. s that all processing apparently occurs at the host Each page of a document is requested sepa rately each search request requires the host to search the article and each summary is retrieved with a separate user request Additionally a request to go back a page requires the system to receive the page again Also the system only allows printing a page at a time or at the Mead central location whose output is mailed to the subscriber The lack of any local processing makes the modem latency very noticeable at all times Finally the only knowledge the system contains is about special fields that exist in each of the libraries files a library is simply a collection of related databases How ever the presentation mechanism does not take advantage of the knowledge Thus a law review article text is displayed with the footnotes in between portions of text This presentation combined with the slow speed make the system annoying to use for reading the actual results of one s search The final system is AppleLink which allows Apple Developers to get technical information communicate with other developers get Apple press notices etc As this is the only system that was written for the Macintosh it is no surprise that it takes better advantage of the Macintosh environment than the previous two systems AppleLink implements both remote and local processing in an efficient manner A user can perform full text searches and receive the
33. server telephone number and the mo dem baud rate An advanced Macintosh user can use a Macintosh Resource Editor such as ResEdit to change the default options MacNews reads the default options from the resource file every time the program is run Once a connection to the BCIS server is established the Options menu item is deac tivated It is activated again anytime the connection to the server is closed The Page Setup allows the user to set the printer default information The defaults are taken from the Macintosh System File thus the user s printing defaults are the same in MacNews Finally the Quit option exits the pro gram A user may also exit by using the query window close box as discussed in the preceding section or typing the keystroke gt Q where ba stands for the Apple Key on the Macintosh keyboard If the user has article windows open confirmation is requested before exiting The first two commands do not have keystroke equivalents as they are not expected to accessed often The Edit menu contains the standard Macintosh text editing commands Copy and Paste These are accessed by the standard Macintosh keystroke equivalents pC and oxV respectively These commands move text to and from the Macintosh TEScrap text scrap pad The Article menu is initially completely disabled as there are no article functions which can be executed until a query is processed and summaries arrive When the summaries are received the Read option
34. titles of the matching documents The user can also request the full text of the matched item However there are three problems with this system First the user does not receive a summary of matched items thus one is often forced to start retrieving the text of the matched item only to determine that it is not of interest Secondly the hierarchical structure of the databases is often confusing and the user must know specifically which directory to search There is no ability to search all the files at once Finally there isn t a concept of separate sections of the document Thus a user is forced to do full text searches even if for example the ability to search a subject field would be much more productive 1 3 Goals The design and implementation of MacNews had several modest goals The first was to see if certain design ideas were both able to be implemented and easily used by a end user The second was to provide the BCIS with a starting point on the Macintosh hardware Not only to make it available to another group of users but also to work on improving its interface Also there was a desire to see if problems that other systems faced could be avoided when attention was paid to both the overall system retrieval design which BCIS has done and to the specifics of an interface which the Macintosh would provide Finally was the personal desire of the author to learn more about programming the Macintosh computer 1 4 Motivation Th
35. vice 36 Bibliography Apple85 Apple Computer Inc Inside Macintosh Volumes I II HI and V Addison Wesley Publishing Reading 1987 Apple87 Apple Computer Inc Human Interface Guidelines The Apple Desktop Interface Addison Wesley Publishing Reading 1987 Chernicoff87 Chernicoff Stephan Macintosh Revealed Volumes I and II Hayden Books 1987 Cote87 Robert G Cot An Automatic News Article Editor Bachelor s Thesis May 16 1987 Gifford87a David K Gifford et al Boston Community Information Sys tem 1986 Experimental Test Results MIT LCS TR 397 August 1987 Gifford87b David K Gifford Robert G Cot and David A Segal Walter User s Manual Version 1 0 MIT LCS TR 399 September 1987 Gifford87c David K Gifford Robert G C t and David A Segal Clipping Service User s Manual Version 1 2 MIT LCS TR 398 September 1987 Gifford88 David K Gifford Polychannel Systems for Mass Digital Com munication MIT LCS TR 420 July 1988 Segal86 David A Segal et al Boston Community Information System User s Manual Version 8 17 MIT LCS TR 373 September 1986 Segal87 David A Segal Sarita Gandhi and Penney Lewis Xwalter Design Notes Programming Systems Research Group Memo June 18 1987 37
36. vior depending on whether or not the presence of the second click was already in the event queue while TEC1ik was running Additionally while the books are a good reference set 1t is almost impossi ble to read through them to learn how to program the system Furthermore these manuals are written for Pascal programmers so when one programs in C they must be careful to make appropriate translations The Macintosh Revealed Chernicoff87 set of books are easier to read to learn about programming the Macintosh However these are also written for the Pascal user Additionally the programming examples provided in Macintosh Revealed tend to contaiu only a single window which can cause the new programmer of a multi window application to head down some blind alleys Finally both of these sets of books tend to include every function provided by the different managers without clearly distinguishing between the high and low level procedures Providing all the functions that are in the system while complete can cause a new programmer to incorrectly interpret which function they should call There should be a better organization more of a top down approach that clearly marks the high level procedure and the one the programmer should call in most cases and then in a separately marked section the low level procedures It also would be helpful if the top level procedure was explained in terms of what procedures it calls rather than 27 providing onl
37. y an English description of what it does 28 Chapter 3 System Operation This section describes the operation of MacNews First the processing of a simple query is presented and then discussion of the speed of operation and fault tolerance is given 3 1 Processing A Query When the user begins MacNews a screen as shown previously in Figure 2 1 is displayed Let s say the user is interested in following the New York Mets to the World Series championship They type mets date date 2 07 in the window indicating their desire read about the last two Mets victories They then Ask the query MacNews starts establishing the connection notifying the user the current state and in the case of long op erations the maximum time that it takes to complete For example while waiting for the server and modem to connect the status message is Waiting for connection May take up to one minute Then the summaries start being received with the user being told the number of matches so far and the number of summaries received When all the summaries are received the status box disappears and the user may peruse the summaries issue a new query or request an article Figure 3 1 shows the query processed and the summaries received If the user was interested about the Mets win over Cincinnati for example they would click on summary 3 and execute Read as the Article menu has been activated in Figure 3 1 as compared with Figure 29
38. zation of the Thesis 0 0 2 System Design 2 1 User Interface e iaa gohan ala eh OE ee ce ead OG 21 i Windows soa sane pa e Se amp a ye ot Mlk Woe dee 212 A Riek Slee NN 2 1 3 Keeping the User Informed 2 2 Program Structure ae AA AAA 2a Eyent Loop AI 22 2 Modem Loop is da TAs 22 0 Data Struct res a Sa ee oe aR e 2 2 4 Modularity 6 oak rado Ss Sek ae 2 3 Macintosh Support wa lt 6 a ack Pale base ep we A 23L Pascal Vd a OSS 2 3 2 The Managers bo a A 233 Serial Drivers y lt ated a a a e 2 3 4 Documentation py ae Se e a Bo eR 3 System Operation 3 1 Processing A Quer ni a a E A 3 2 de io IA A A 33 Rob stn ss d o ge a IA E A A 4 Summary 4 Future Research 4 24 45 48 Ac ee a a Oe A 42 Conclusions 2 eGo u Bae nh wee OS a ee ay List of Figures 2 1 The Query and Summary Windows 14 2 2 The Window Data Structure o lt 23 2 3 The Summary Data Structure 24 3 1 A Processed Query 30 3 2 The Received Article o o 32 Chapter 1 Introduction Our thesis is that the Apple Macintosh line of computers provides a good basis for a personalized information service The Boston Community Infor mation System BCIS Project provided both the original idea and frame work for this project In order to test our thesis we have designed and implemented a personalized information system calle
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