Changes between Version 26 and Version 27 of BluePrint/Importer


Ignore:
Timestamp:
01/22/11 10:18:43 (11 years ago)
Author:
Pat Tressel
Comment:

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  • BluePrint/Importer

    v26 v27  
    2424Having the data parsed into an !ElementTree allows [wiki:S3XRC S3XRC] to handle all the database integrity & framework rules.
    2525
    26 Q: Is this correct? !ElementTree without pointers between separate trees does not seem to have a way to encode a directed acyclic graph. A general database schema is a DAG plus self-loops (references from a table to itself, so long relations among elements are not cyclic). (For instance, consider volunteers. They have components via pe_id. They also have references to zero or more elements of the volunteer skills table. Other volunteers point to those same skill records. Thus there are multiple roots -- the skills -- to the tree of volunteers. The same structure occurs in inventory, where catalog items are referenced by multiple order items, but order items are also components of orders. In these cases, there isn't a (clean) way to pick one root for a tree. If we decided to have an skill category table, then we would have diamond-shaped DAGs -- a volunteer could point to several skills, and those skills could point to a common category.) For output, this is not relevant because the records will have their primary keys and foreign keys available. It's only an issue when creating a collection of dag-structured data, as no actual keys have been assigned yet. This is not hard to overcome -- it just means adding placeholder keys to represent the linkage between records in separate ElementTrees. There are examples of DAG representations and algorithms -- a search for "xml directed acyclic graph" will turn them up.
     26 Q: Is this correct? !ElementTree without pointers between separate trees does not seem to have a way to encode a directed acyclic graph. A general database schema is a DAG plus self-loops (references from a table to itself, so long relations among elements are not cyclic). (For instance, consider volunteers. They have components via pe_id. They also have references to zero or more elements of the volunteer skills table. Other volunteers point to those same skill records. Thus there are multiple roots -- the skills -- to the tree of volunteers. The same structure occurs in inventory, where catalog items are referenced by multiple order items, but order items are also components of orders. In these cases, there isn't a (clean) way to pick one root for a tree. If we decided to have an skill category table, then we would have diamond-shaped DAGs -- a volunteer could point to several skills, and those skills could point to a common category.) For output, this is not relevant because the records will have their primary keys and foreign keys available. It's only an issue when creating a collection of dag-structured data, as no actual keys have been assigned yet. This is not hard to overcome -- it just means adding placeholder keys to represent the linkage between records in separate ElementTrees. There are examples of DAG representations and algorithms -- a search for "xml directed acyclic graph" will turn them up.
    2727
    2828- this also allows Eden's Importer tool to be used as a Mashup handler for other systems (such as Agasti) by posting the data back out.