TweetFollow Us on Twitter

IAC in Sys 7
Volume Number:5
Issue Number:8
Column Tag:Developer's Notes

Related Info: Apple Event Mgr PPC ToolBox Event Manager Edition Manager

Apple's IAC in System 7

By Frank Alviani, Contributing Editor, Waukegan, IL

Inter-Application Communications - The Future is Rapidly Approaching

It was just one year ago that my first article on Inter-Application Communications was printed here in MacTutor. In it and the succeeding two articles Paul Snively and I described and implemented a facility for allowing programs to be written that could automatically communicate without bothering the user. Apple has “validated” that concept by making it a centerpiece of the upcoming System 7.0. This article will be a short look at the approach taken by Apple, and how it is going to change the face of the Macintosh forever. (If you work in Word 4.0 with Superpaint 1.1MS, the linked combination gives some hint of the feel of the linked-document future we are heading towards!) It is NOT an introduction to the actual programming interfaces.

In addition to the new world Apple is entering, DEC has an analogous concept called Compound Data Architecture (CDA). The similarities between a suite of IAC-linked documents on a Mac and a DEC compound document are enough to strongly suggest that once both are established in the marketplace, it will be reasonably straightforward to convert between the two systems. This is a non-trivial operational concern in mixed shops, and important from a marketing viewpoint. I would be mildly surprised if the two companies didn’t work together to ensure the interconvertability of their systems.

Apple has taken a layered approach to implementing their IAC facilities; this is consistent with the approach taken with the other toolboxes and a natural division based on the intended usage for each layer. The material that appeared here in MacTutor corresponds to the PPC-toolbox level in the Apple scheme.

Figure 1 shows the layering designed by Apple, intended to show how interfaces on one layer depend on the next layer down, and how the interfaces at the same level serve different aspects of a common requirement.

SuperPaint!Me:Write Ups:Apple-IAC Illustrations!Draw(107,129:203,179)

SuperPaint!Me:Write Ups:Apple-IAC Illustrations!Draw(103,56:350,178)

The PPC Toolbox

The lowest level provides the raw messaging tools: direct communication and “store and forward”. This level is not intended for user-interface usage. It corresponds most closely to the SAWS IAC system, although the details of the Apple implementation haven’t been spelled out enough to tell how similar the internals are (I suspect they are significantly different, since certain of our IAC facilities are placed in different layers in the Apple software).

This level services two classes of clients: the upper layer of the IAC system software, and non-event based “chunks o’ code” such as RDEVs, DAs, etc. In a sense, all code executing on a Macintosh will be on an equal footing, able to talk with any other code executing at the same time or in the future. It is very important to note that programs and processes do NOT have to be on the same machine to take advantage of the PPC facilities.

These tools open up various interesting possibilities:

• Programs would be able to preserve “state information” across sessions by using the store-and-forward facilities to send messages to their future incarnations.

• Cooperation between programs on networked machines - well beyond the capabilities of today’s programs such as Timbuktu - becomes practical. For example, an artist can be building an illustration for an article, on machine A, while the article is being written on machine B, and the illustration would be in place in the article even while being drawn. This could allow unprecedented cooperation.

• Control panel devices could be used to actually control executing programs, etc. For example, an intercom is one possible such device.

The “Higher Level Events”

For the programmer, there is a significant extension of the event manager: “higher level events”. This is intended mostly for “below the surface” program-to-program requests, many in the form of remote menu-command executions.

In order for higher level events to be extensible for the future, several fields in the existing message record have had additional usages layered on top of their existing definition (in much the same way that the Text Edit toolbox was extended).

As shown in Figure 2, the “message” and “where” fields are redefined when interpreting a higher level event. The “what2” field - message class - identifies the protocol that defines how the specific message in the “what3” field is to be interpreted. How are those message classes going to be assigned so there won’t be anarchy and inadvertent duplication?

Apple long ago put a workable system in place when it decided to use 4 character fields to identify resources, application signatures, etc., and that same system will be used here. Applications will use their signature (‘MACA’, etc.) as the message class they send; Apple is, as usual, reserving all-lower-case combinations for themselves. For each class of messages, there are 232 possible messages.

I expect that at first each publisher will independently define sets of messages that will allow his applications to cooperate. However, there was discussion at the developers’ conference of perhaps arranging a conference on AppleLink to support the growth of a set of industry standard, publisher-independent messages. This would be of enormous benefit to the user, since it would make the development of a universal scripting language (see the note about AppleScript later) much more likely.

Apple will define the message class roughly corresponding to the File and Edit menus (calling their protocol AppleEvents™ and using the signature ‘stdr’); the remaining classes are defined at the discretion of the developers.

The general method of using higher level events is the same that’s used for existing events - WaitNextEvent to accept events and PostEvent to send them. There are few options that don’t exist in System 6, but they don’t change current fundamental techniques.

Certain aspects of this API are still not completely worked out, and will require considerable care to do properly. For example, we now have the possibility of an entirely new class of VandalWare: programs maliciously misusing higher level events. Methods for assuring you are certain of who’s sending a message before you act upon it will be required.

The Publish-and-Subscribe Interface

The segment of most interest to the user is the “publish-and-subscribe” support intended to standardize the user-interface approach. This resembles the technique used in the SAWS IAC driver, and in fact some of the terminology is the same.

The phrase “publish-and-subscribe” was carefully chosen to suggest to users that there can be a slight delay between when data is published and when it is received; it also suggests that there can be geographic separation between the data source and destination.

Apple’s goals for the interface are as follows:

• It must be generalizable - usable for all applications

• It must be scalable - capable of dealing with large amounts of data (for database or multimedia work, for example)

• It must work cleanly with the existing Mac interface

• It must work over the network to support networked cooperative tasks.

Like the SAWS IAC suggested interface, the fundamental units that are linked are sections, not documents. A document can have any number of publishing sections and subscribing sections, and can in fact even subscribe to itself (a wonderful fractal demo took advantage of this fact!) The IAC toolbox called the Publication Manager includes support for resources that are required to track the status of these sections, thus simplifying the programming task. The sections drawn during the demos at the developers’ conference were all rectangular, but I don’t believe that is required (if it is it should be generalized).

Like the SAWS IAC driver, the Apple IAC support can be viewed as an extension of the scrap manager (which is in fact shown in Figure 2). This suggests that applications need the same types of facilities to support IAC - such as the ability to handle at least the standard data formats, such as PICT and TEXT. This minimal level of support alone can go a long way towards making sure that relatively arbitrary combinations of applications can be “integrated” smoothly; your application doesn’t need to know how to interpret every data format in the new universe to fit in.

Unlike the SAWS IAC driver, the published data is kept by Apple in external files. These “pub files” are standard, named files that have their own Finder icon. This approach provides considerably greater generality: by putting “pub files” on a file server such as AppleShare, any number of documents can subscribe to the same data. As with the SAWS IAC driver, the exchange of data from publisher to subscriber can be asynchronous. The System 7.0 enhancements to the file manager provide file-ID facilities that are location-independent, so that publication files can be moved around on a single volume without confusing the client (publisher and subscriber) applications.

Unlike the suggested user interface for the SAWS IAC driver, Apple’s interface explicitly requires intervention for data to be published; the suggested action is when the Save command is invoked. Subscribers in open documents are notified immediately; subscribers in closed documents are notified when that document is next opened. Explicit intervention was chosen to simplify the application’s programming model and to avoid problematic recursive situations. My experience in writing the original MacTutor sample program suggests that this is a good solution; deciding automatically when the fresh data is cooked enough to publish is trickier than it looks, and depends a good deal on the type of data being manipulated. My only suggested extension would be to also have an explicit “update publication” command as an alternative for programs where saving is a time-consuming operation, such as databases.

The subscriber, in the Apple model, is a somewhat passive participant; it normally will just display the data retrieved from the pub file. The user interface guidelines, however, do support the idea of adornment - style changes made to text, etc. by the subscribing application before displaying the new data. Scaling and clipping would be among the appropriate adornments to apply to graphic data.

A very useful facility available to a subscriber is “go to publisher”, possible because of the backlinks between files. Implemented according to the guidelines, this transfers control to the publishing application, after the document has been opened if necessary, and the section has been scrolled into view.

Establishing a linkage between two documents is straightforward:

• The user selects some data; the application calls the publication manager to create the section-tracking resource.

• The “publish” command is invoked. The application brings up a standard-file like dialog to name the “pub file”, and then creates it.

• The user goes to the destination document.

• A section is selected to be a subscriber; the application calls the publication manager to create the section-tracking resource.

• The “subscribe” command is invoked. The application brings up a standard-file like dialog to select the “pub file”, and then reads it.

• The link is established.

Again, the API is not finalized and there are rough edges that will need to be smoothed out before System 7.0 is unleashed on the world. For example, there is no record of the last time a pub file was used, so that there is no easy way to detect “stale” pub files. If you think junk files accumulate on your hard disk, with only you living there, think of what some poor AppleShare administrator is looking at...

Conclusions

The design of the IAC support in System 7.0 was very well done. It will be a reasonable task to incorporate IAC support into existing applications; interface decisions may be more work for some applications than the actual coding. The facilities possible are exciting even to jaded developers - the IAC session kept being interrupted by applause!

In the long run, for anything more complex than a letter to Aunt Sybil, suites of linked documents are going to become the norm due to the convenience of working with your personal favorites in each required specialty. This reduces somewhat the attraction of all-in-one programs such as Lotus’ Jazz and Microsoft Works, although it may prove that requiring no configuration at all is enough of a feature to support a worthwhile market.

Applescript is a nebulous future concept that kept surfacing during the developers’ conference without ever being clearly defined. It sounds like Apple’s syntactic Holy Grail - a single language syntax that is usable for MPW scripts, SADE scripts, and the user’s control of the machine as a whole. One planned feature appears to be that it will have facilities for users to send “higher level event” messages to programs. This would give them text-based application-independent macro capabilities, rather like Tempo.

As an example of what all of these facilities together promise, imagine you have investments in several high-tech stocks that tend to move wildly all over the chart. Keeping peace in the house requires that you prepare a chart every so often to prove that poverty isn’t just around the corner, and so you decide to automate the process to make it less of a nuisance. All it requires is a quick script that does the following:

• At midnight on the 1st of each month, launch your favorite telecomm program with a program to dial up your data service and download all the prices required.

• Launch your wordprocessor with the basic stock report ready to go, including the subscribers for the data values and chart of price gyrations.

• Launch your spreadsheet with a worksheet and macro that loads the new data and charts it. Both the data cells and the chart are publishers, so you save the worksheet and publish the selected data and chart.

• The stock report updated automatically, so just order it to be saved and printed.

• Close all the applications.

MacTutor programmers, of course, will almost instantly be creating scripts of far greater complexity, and there will no doubt be a column devoted to AppleScript programming, but this gives you some idea of the potential that will be available to us in the near future.

In a couple of years we will probably be working in an environment that has some characteristics of the traditional mini-computer: (1) Multiple “parallel” processes, with communications between them, and (2) At least 1 powerful scripting language that allows flexible automation of repetitive actions - but with the addition of almost universal data-interchange formats, a huge variety of off-the-shelf software, and a consistent user interface.

The change from single-program to multi-program workstyle is not going to be without experimental evolution unprecedented in computer history; we’ve never had enough power available on a widespread basis to make this new mode of working feasible. There will undoubtedly be several styles of integration at first, until the market determines which is most workable, for example. There may be conflicts for a while between message sets that make it a little rocky to integrate arbitrary combinations of applications. In spite of these caveats, I am looking forward eagerly to an IACed universe - and so should you.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

FotoMagico 5.4.1 - Powerful slideshow cr...
FotoMagico lets you create professional slideshows from your photos and music with just a few, simple mouse clicks. It sports a very clean and intuitive yet powerful user interface. High image... Read more
Espresso 3.0 - Powerful HTML, XML, CSS,...
Espresso is back. For people who make delightful, innovative, and fast websites -- in an app to match. Espresso helps you write, code, design, build, and publish with flair and efficiency.... Read more
Spotify 1.0.51.693. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
Gutenprint 5.2.12 - Quality drivers for...
Gutenprint is a suite of printer drivers that may be used with most common UNIX print spooling systems, including CUPS, lpr, LPRng, or others. Gutenprint currently supports over 2000 printer models.... Read more
Firefox 52.0.2 - Fast, safe Web browser.
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
Google Chrome 57.0.2987.133 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
RapidWeaver 7.3.3 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
Chromium 57.0.2987.133 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 27.0.2987.133: Note: This update has no Flash... Read more
Lyn 1.8.8 - Lightweight image browser an...
Lyn is a fast, lightweight image browser and viewer designed for photographers, graphic artists, and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it delivers... Read more
Adobe Animate CC 2017 16.2.0 - Advanced...
Animate CC 2017 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Flash Professional customer). Animate CC 2017 (was Flash CC) lets you... Read more

Dynasty Warriors: Unleashed arrives on m...
No one does mindless hack and slash quite like a Musou game. What's more fun than single-handedly chopping your way through hundreds of enemies? Now, for the first time ever, that unrivaled experience goes mobile with Dynasty Warriors: Unleashed.... | Read more »
Crash of Cars beginner's guide
Crash of Cars is a fun new entry in the realm of multiplayer beat 'em ups. It's basically bumper cars off the rails -- players drive around in vehicles of their choosing -- anything from a mini-van to the weinermobile in all of its glory --... | Read more »
Dynasty Blades new update introduces a n...
Sharpen your weapons -- Dynasty Blades is back with new and improved hack n’ slash stylings. The Romance of the Three Kingdoms-inspired action MMORPG introduces a bunch of fun new features in its latest update. For the uninitiated, Dynasty Blades... | Read more »
Meganoid(2017) (Games)
Meganoid(2017) 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: LAUNCH DISCOUNT 20% UNTIL APRIL 2nd! Support, tip and tricks: http://www.orangepixel.net/forum/ Subscribe to our newsletter... | Read more »
Telltale's Guardians of the Galaxy...
Telltale will be releasing their rendition of Guardians of the Galaxy later this month. The first episode, Tangled Up in Blue, features familiar faces including Star-Lord, Groot, Rocket, Gamora, and Drax. If the first episode's title is any... | Read more »
Royal Dungeon (Games)
Royal Dungeon 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: The king and his queen are trapped in their castle which suddenly turned out as a very dangerous place. The goal is to escape... | Read more »
Tom Clancy's ShadowBreak is a real-...
Ubisoft is treating Tom Clancy fans to the series' very first mobile-exclusive game in ShadowBreak, a real-time, multiplayer shooter in which players snipe at enemies in fast-paced tactics-driven combat. [Read more] | Read more »
Power Rangers: Legacy Wars beginner...
Rita Repulsa is back, but this time she's invading your mobile phone in Power Rangers: Legacy Wars. What looks to be a straightforward beat 'em up is actually a tough-as-nails multiplayer strategy game that requires some deft tactical maneuvering.... | Read more »
Hearthstone celebrates the upcoming Jour...
Hearthstone gets a new expansion, Journey to Un'Goro, in a little over a week, and they'll be welcoming the Year of the Mammoth, the next season, at the same time. There's a lot to be excited about, so Blizzard is celebrating in kind. Players will... | Read more »
4 smart and stylish puzzle games like Ty...
TypeShift launched a little over a week ago, offering some puzzling new challenges for word nerds equipped with an iOS device. Created by Zach Gage, the mind behind Spelltower, TypeShift boasts, like its predecessor, a sleak design and some very... | Read more »

Price Scanner via MacPrices.net

Deal alert! 13-inch 2.0GHz MacBook Pros now f...
B&H Photo has lowered their price on 13″ Apple 2.0GHz MacBook Pros to $225 off MSRP through midnight tonight (3/30/17). Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz... Read more
1.4GHz Mac mini on sale for $399, $100 off MS...
B&H Photo has the 1.4GHz Mac mini on sale for $100 off MSRP including free shipping plus NY sales tax only: - 1.4GHz Mac mini: $399 $100 off MSRP Sale ends on March 31st. Read more
13-inch 128GB MacBook Air on sale for $849, s...
B&H Photo has lowered their price on the 13″ 1.6GHz/128GB MacBook Air to $849, or $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/128GB MacBook Air (MMGF2LL/A... Read more
Is Apple Planning An iPhone Based Modular Doc...
Today’s more powerful and larger-screened smartphones and phablets are becoming the default anchor computing device for more and more users computing devices, but even a five or six inch panel is not... Read more
Razer Launches New Razer Blade Pro World’s Fi...
Razer, the gaming and high performance hardware specialists, have announced the new Razer Blade Pro laptop — the first laptop to be qualified for THX Mobile Certification, an accreditation reserved... Read more
Gro CRM’s Apple Small Business Mac And iOS CR...
Gro Software, developers of the Mac CRM software for small business and enterprise, are included in FinancesOnline 2017 CRM Rising Stars and Great User Experience lists by business software review... Read more
Deal alert! 15-inch and 13-inch MacBook Pros...
B&H Photo has the new 2016 15″ and 13″ Apple MacBook Pros in stock today and on sale for up to $200 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more
Save up to $420 on a new MacBook Pro with App...
Apple is offering Certified Refurbished 2016 15″ and 13″ MacBook Pros, including some Touch Bar models, for up to $420 off original MSRP. An Apple one-year warranty is included with each model, and... Read more
12-inch 1.2GHz Retina MacBooks on sale for $1...
B&H has 12″ 1.2GHz Retina MacBooks on sale for up to $200 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 12″ 1.2GHz Space Gray Retina MacBook: $1449 $150 off MSRP - 12″ 1.... Read more
Is A New 10.5-inch iPad Still Coming In April...
There was no sign or mention of a long-rumored and much anticipated 10.5-inch iPad Pro in Apple’s product announcements last week. The exciting iPad news was release of an upgraded iPad Air with a... Read more

Jobs Board

Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
Desktop Analyst - *Apple* Products - Montef...
…technology to improve patient care. JOB RESPONSIBILITIES: Provide day-to-day support for Apple Hardware and Software in the environment based on the team's support Read more
*Apple* Mobile Master - Best Buy (United Sta...
**493168BR** **Job Title:** Apple Mobile Master **Location Number:** 000827-Denton-Store **Job Description:** **What does a Best Buy Apple Mobile Master do?** At Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.