[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XLink transformations
Let me go back to the list with this to keep up with the ongoing thread. I can't say precisely what XLink buys you except a spec, but if you need to forge ahead, you have to trust your own resources and ignore the specification processes of the W3C, or you have to wait. As John Schlesinger and others point out, relational systems are more reliable with respect to transform operations at this time. Caveat emptor. Nothing being discussed in this thread is new material. The issues of name, location, and identity as they affect reliable addressing are known. Let me review the XLink spec again so I don't confuse what it says from what I learned from Hytime. In my opinion, the basics are: 1. If you transform, you must define the characteristics of operations over the transformed set. Add, Delete, Append, Copy etc. are known operations with regards to identity and reliable addressing. 2. If you cannot guarantee identity, then copy and create a new instance with a new identity. At this point, the relationship to the namespace of the record of authority must also be established: a: transform the schema link to point to an alternative schema b: transform the schema and preserve identity but lose information c: transform both and preserve information and identity Note: often such operations require querying the actual system containers for existence information, to reliably create new containers, etc. It is difficult to build a completely interoperable system of systems that does not use local systemic resources. Maybe impossible. This means apriori knowledge of the resultset such that the transformed instance by rule is automatically an instance of a known schema or a new schema is created or the transformed instance is only lexically valid as in the case of a view whose existence is temporally limited and therefore does not need a schemas. Links can have spatio/temporal properties - defined in the vancouver presentation on views over documents. Timestamping is vital if you want complete rollback. It isn't essential to the link but can be useful as an additional property on linkbases. Hidden couplers are the dilemma in operational analysis of the system performance in timestamped system. As you point out, there is a relationship between transform and schema such that a typed link or an attributed link may be key to declaring the variance rules. Because each locator type has variable sensitivity to transform operations, it must be accounted for in the design and each operation type may be more or less reliable given the locator type. For example, deletion affects any locator but in a given identity and the scope of uniqueness, different locators are more sensitive to it. Most designers will want to use multiple means to establish identity and by redundancy reduce sensitivity. This is clear in a relational system in which a record can have a generated primary key for idenity in the local set (autonumber), but secondary record keys which are used to create relationships among records in the same or different tables (morphological for multidimensional sets, or simple named fields with copied values). OLAPs are most interesting in this regard. Invariance with regard to transform is a known problem with known solutions. Specification remains an ongoing and reentrant task as different groups learn the solutions at different times. Len Bullard Intergraph Public Safety clbullar@i... http://fly.hiwaay.net/~cbullard/lensongs.ram Ekam sat.h, Vipraah bahudhaa vadanti. Daamyata. Datta. Dayadhvam.h -----Original Message----- From: Steve Boyce [mailto:SteveB@h...] With regard to XLink, I couldn't see in the end what the XLink spec actually buys for me. I can see the need for XPath but not XLink.
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|