I think I need a clearer picture of what you want to do here.
WIth this type of many to many relationship, you would usually use an Item layout with a portal to "History" to see all the Locations linked via history to Item and the reverse set up on a Location layout would list all the items linked to that location record.
What I don't see from your post is from what table/record context you want to base your layout with the tab controls since the layout doesn't appear start from any one Item record nor any one location record.
Can you explain in more detail what you want here? It might help to explain how this join table represents a "History" of the other two tables.
I want to document any change that might occur to an item such as condition or calibration status, and any change to it's location(if it gets moved), or conditions at that location. From the other direction, I would like to know what Items have been at a specific location and when they were there.
I originally tried to do this on a tabbed layout pointing to the items table. Items were on one tab and locations were on the other tab. I couldn't get the portals to display the info right. I was able to show changes in locations for an item, but not for changes in items at a specific location.
As you wrote,
"WIth this type of many to many relationship, you would usually use an Item layout with a portal to "History" to see all the Locations linked via history to Item and the reverse set up on a Location layout would list all the items linked to that location record."
I think you answered my question, but just to be sure: no bi-directional information flow or reverse point of views using portals in each tab of a tabbed layout part in a single layout?
It's not really (IMO) a matter of "bi-directional flows of information", it's a matter of establishing the correct context so that you can "see" the data that you want.
"I was able to show changes in locations for an item, but not for changes in items at a specific location."
In what table did you record these "item changes"? As best I can follow, these changes would need to be part of the History table, correct? If so a portal to History on an Item layout should be able to list both the location and the "item changes". If you then establish a filter for the portal with a location drop down or place several such location filtered portals on different tabs, that should produce what I think you are requesting here.
Filtering a portal is easier to set up in Filemaker 11, but it can also be set up for older versions of filemaker.
It's back to the trenches for me; I still have a large gap in my understanding of tables, table occurences, layouts pointing to tables, etc. I appreciate your willingness to help. I am going to try some more to get these portals to work like I want in the comming week, and if I am still stumped, I'll try to repost with what I learned.
I am using FMP 10 at work, so portal filtering is a technique that hopefully I will learn later on after I get these foundational concepts firmly in place.
Download this file: http://www.4shared.com/file/4zHEUo0M/ItemLocationHistory.html
And check out the two portals on the Item layout.
How close do either of them come to what you want?
The second portal is a filtered portal using a technique that works with older filemaker versions as well as filemaker 11.
Thanks for the tutorial. It is slowly sinking in. I have trouble getting the ERD (such as it is) out of my head when working in the relationships graph. As long as there are just a couple of TOs, I do ok, but when the TOs start zinging off like an unfriendly ride at the county fair, I can't seem to follow it all. I looked at the file you graciously put together and have a better idea of portal filtering than I did before.
In that example, the left portal works just as I would expect and I have been able to do that from my existing skills set. But I want the right portal to show all the trucks that have been at the current location (and when they were there). I can do this from a separate location layout - and can almost say it makes sense, but can it be done from a single items layout?
I often color code my TO's so that all TO's with the same data source table are the same color.
Yes, you can do what you ask, but you need a TO with a different relationship. Since you want to see all trucks, you need a relationship that does not match by truck ID.
In my example, you'd just delete the first pair of match fields so that the relationship matches records only by the location fields.
In filemaker 11, you could match with the cross product operator (X) instead of = and move the filtering into an expression in portal setup.