LIMITATIONS

The current version of Istar has a number of limitations. Some of them include:

# Cannot import to KB from another KB.

# The FIRSTOK inference method (Present Each To User) not yet implemented.

# Cannot use the Import-Text yet on items.

# Cannot at present delete value names from an attribute type; can only add them.

# Certain obscure conversions between value types do not work fully; best to try them out before you use them. e.g. Float to Odds.

# The new text/document facility is at present very limited.

BUGS

This is a list of some bugs you should be aware of.

# (Rare but unavoidable if you need it) Multiplying two ratios in which one has a negative number does not work. 1/-6 times 12/1 gives 6/65533.

# (Harmless nuisance 'feature') If you create a new attribute type and set its pens, and then create a free attribute item type for it, then sometimes boxes of this will be the new colours and sometimes not. What happens is that if you set the pens and hit the 'Create Free Att Item Typ' button, it is created with the old pens - because it only copies the new pens etc. across when you hit the OK button. But if you do not hit that button but hit OK after setting the pens, and create the FAIT afterwards, then it will have the new pens. Note that from v1.083 onwards, if you hit the OK button without a FAIT it will ask whether you wish one created - and ones created there will have the new pens.

# (Harmless nuisance) If you start to create a new item type (and relationship type) then hit 'Cancel' the type is not actually deleted; you get a type with a null (dash) name and have to hit the 'Rid' button to remove it. This is because it first creates a null-named type and then allows you to change its details.

# (Nuisance) Recently I had things like DirOpus loaded, and went to load up three KBs with full size easels. Then tried to 'rid' a KB and nothing happened. Tried to quit and nothing happened. Because I had run out of Chip memory and the small "Is it OK to rid the KB?" panel would not come up! (Chip memory was down to 13k.) But beware: there is no warning, and none can be given because the warning panel will not come up.

# (You probably will never notice it) It has been reported that Istar does some Enforcer hits. On investigation, these are all reads of memory around address zero; no writes have been reported, so it should be OK. The main one is when the file requester comes up; it seems to read a string at address 0. They are being invetigated.

# (Harmless limitation) Various buttons are not operative yet:

# (Harmless limitation) Conversion Float to Odds does not work.

# (Could lead to unexpected results in your KB) When a conversion does not work you do not get any warning of this fact. What happens depends on the type of conversion, but often the result holds the bit pattern of the uncoverted value, which might of course seem like rubbish, or might hold 0. 30 July 1996.

# (Nuisance, unlikely to be encountered) I have a couple of old KBs which have a 8-colour easel and in which pen 7 is white, like the background colour, so things drawn in this pen appear invisible. I alter the colour on the Easel Info menu, and save the KB, but for some reason it doesn't save properly. The reason is that in older KBs the palette was stored differently.

CRASHES ENCOUNTERED

(Please: it you have it crash on you, send me details. Istar@basden.demon.co.uk). The following crashes I have experienced and not yet found the cause of.

# (1.04: Probably OK from 1.05. Can cause crash, but avoidable) The resize KB facility can be a bit fragile and can cause a crash in version 1.04. This is because if the KB increases in size it moves in memory and therefore all the pointers into it must all be changed. I *think* I have found all these, but I did once get a guru 81---5 (attempt to free memory already freed) when I quit the program. I have a feeling it was something to do with resizing. For this reason, before you attempt to resize you should close down all panels except that for the KB itself.

BUGS FIXED

FIXED BY VERSION 1.085 February 1998

# (Can be misleading to user) The explanation of a relationship type is only accurate for simple types; the facility is yet to be finalized. Version 1.04 and earlier.

# (Crash, avoidable, unlikely to be encountered) If you try to save the easel as an IFF file without having iff.library in libs: version 1.084 and earlier would crash. Fixed 1.085.

FIXED BY VERSION 1.084 February 1998

# (Avoidable error in Version 1.08-1.083) If you draw a link in inverse direction (from cons box LHS to ante) then though it looks, and acts visually like an inverse link, it actually is a forward link in the data structures. Avoid by not drawing inverse links. Fixed with version 1.084, and not a problem pre 1.08.

FIXED BY VERSION 1.083 (Feb 98)

# (Nuisance Crash, frequent.) V1.08 (both Dec97 and Jan98 versions) crashed when you hit 'Delete' on Attribute Action Panel. Now it doesn't.

# (Avoidable nuisance Crash.) In V1.08 (both Dec97 and Jan98 versions) if you bring up, say, the Attribute Details Panel and hit the Type button, up comes a simple list of types from which you can choose. In V1.08 (but not before) you could then send the main panel away and the list remains - and if you then hit its 'OK' button Istar would crash. Corrected.

# (Slightly dangerous nuisance) In V1.08 and earlier if something was deleted, but there were panels around that referred to it, then not all were removed - which could lead to a crash. Now, if you delete something, and a panel is up that is for that thing then the whole panel is removed. And in most cases, if a list gadget refers to it, its entry in the list is removed.

FIXED BY (Jan 98) VERSION 1.08

# (Rare nuisance to version 1.08; fixed in version 1.083) If you make up an item type with attributes, and then rearrange the attributes then the resulting box group has the attributes in the wrong order.

# (Only in the early version of v1.08 uploaded around Christmas 1997: Occasional Crash; the real version, uploaded 3-Jan-98 should be OK) If you tried to change the attribute value type on the attribute details panel it could crash. Caused by calling a routine with parameters the wrong way round. Action: Download the new version, or avoid changing value type.

# (Only in the early version of v1.08 uploaded around Christmas 1997: Minor Nuisance; the real version, uploaded 3-Jan-98 should be OK) In new KBs the attribute given to Text Fragment and Insert item types are wrong.

FIXED BY (Early) VERSION 1.08 (Dec 1997)

# (Cosmetic, harmless; PARTLY FIXED) Version 1.02: A Form item does not space out the value gadgets properly always. Some of them are too tall and overlap others. 2 August 1996. This is being investigated. It has been partly cured (still untidy) in Version 1.03.

BY VERSION 1.06 (Feb 1997)

# (Nuisance to end user in versions 1.05 and earlier) The Chooser inference method would only reset its attribute to unanswered every other time, not every time. A bug in dealing with first (index) antecedent. Fixed after 1.05.

# (Nuisance in version 1.04, corrected 1.041) A bug entered V1.04 that I found two days after placing it on Aminet! It would not allow you to change value types in the Attribute Details panel. Immediately corrected it and placed new version 1.041 on Aminet.

# Bug when adding new attribute to items with shown attributes. The new one would be placed on top of old one. Now it's OK; they are placed in a vertical column.

BY VERSION 1.05 (Jan 1997)

# (A freeze if not a crash!) There's an odd sort of bug when Istar runs up on some machines. It's perfectly OK on the three 1200s that I have tried it on (020 and 030). But when I run it up on my 4000 it comes up with the main easel and the SIT (Select Item Type) panel and all, but won't draw, and won't respond to clicks on the main control panel. Until, that is, I click around on the SIT panel. Sometimes dragging the listview scroll bar around helps, and then clicking to select an item type, sometimes clicking on the 'New' button. Then there is a delay of a few seconds, and everything starts as normal. Strange. But, as I say, on my three 1200s it seems perfectly OK. 9.9.96: I have found a possible cause of this and corrected it, but have yet to try it out. No, it does not work yet, Nov 1996. I got an email to say that it froze their 3000 too. While preparing 1.05 I found a slight error in the code, changed it, and then it seemed to work on my 4000 and 3000. So hopefully it's now OK.

BUGS FIXED BY VERSION 1.04 (Nov 1996)

# (Harmless Cosmetic) When you change the name of an item, it doesn't redraw with the new name until F1 or next load. Attribute names refresh OK. Version 1.03 and before.

# (Harmless Nuisance) When trying to resize an item using right-shift, you have to place the mouse *exactly* on the edge of the box: hit-vicinity is zero. Otherwise you will start to draw a link or move the box; if that happens then just hit escape. Version 1.03 and before. (Actually, it was not the need for exact positioning: it required a second attempt. A bug in window switching.)

# (Harmless cosmetic) When you start drawing on the main easel and abort by hitting escape you get a beep-flash. Don't worry: nothing is wrong. Version 1.03 and before.

# (Harmless nuisance) New facility in Version 1.03, Resizing of KBA, doesn't work; it leaves the KBA as it is.

# (Harmless nuisance) The Backup button on the KB Area panel (Version 1.03) has no effect.

# (Harmless cosmetic nuisance) Renaming the KB Area sometimes leaves rubbish characters at the end. Version 1.03.

# (Harmless, cosmetic) When you reset an attribute that is in the middle of a network it propagates the unanswered status OK, but does not show this change in status on the easel. So if the Att is e.g. Bayesian and Shown it retains the solid black line.

# (Frustrating but probably harmless) Version 1.03: When you have two KBs active, and go to the Item Type Panel, and hit the Left or Right RelTypes buttons nothing happens. But when you get rid of all but one then the list of RelTypes appears OK. 5 August 1996. This is being investigated.

BUGS FIXED BY VERSION 1.03 (Sep 1996)

# FIXED. Version 1.02: Never press the three right hand gadgets of the name/meaning bar unless a knowledge base is present. It will probably crash the machine or send it into an infinite loop since they assume one is present. 2 August 1996. This has been corrected in version 1.03.

# Version 1.02: When redirecting a link the DAG cycle detection algorithm sometimes says there is a loop when there is not. 2 August 1996. This is being investigated. 12 September 1996: I have found the bug: it occasionally searched from the wrong node. Now it should be OK in Version 1.03.

# Version 1.02. It occasionally crashed while linking two items. I have found a bug that could do this, and corrected it. Version 1.03 should be OK.


Copyright (c) Andrew Basden 1997.