Hello Freek, Was not at the meeting, but we plan to read very soon the document John V. sent (viewing from Stitching framework). And if necessary provide feedback. Freek Dijkstra wrote:
- Freek: Port is unidirectional (not bidirectional. This suggestion is based on experience with multicast, and complex adaptation stacks, which were harder to describe using bidirectional Ports. Suggested by Guy)
Fully support that.
- Martin: Add time-based information. Each network object can point to _multiple_ time intervals (with start time and end time). The meaning is that if "the network object is available" during these time interval(s). It was shortly discussed that time intervals can be used for both inventory management as well as reservation data, though it is not yet entirely clear if this can be described with the same type of relation from network object to time interval.
Can understand this point. And it has some relation with the points I have (due to work in the Stitching Framework: http://www.geant2.net/upload/pdf/GN2-07-066v5-DJ3-5-3-Report_on_Testing_of_T... ). The below points have perhaps a lower level relation with the present work status in NML, but I still want to mention it. The Stitching framework will be able to work with any definition language (like XML) as long as it has the concept that an object not only has properties like Name (e.g. 'Speed of interface') and Value (like "1 Gbit/s or 10 Gbit/s"), but that other semantic related properties can be attached to an object (like "What can adjust the Value?": For intance what can change the speed of an interface"; e.g. human, ethernet protocol, etc.). In the stitching framework the Name of an object (which is also a property) does not have to be defined by the way. This make the framework open to new technologies (where standards are not yet set;in case of research/testing). The framework just looks for objects that have the same name in Peering domains and then using the other semantic properties determines if they can be stitched/connected and how. That aspect of additional semantic properties is the most important part of the Stitching Framework and should be part of the semantics of a description language. This part is quite often missed the semantics in a network description languages, correct? In the Stitching Framework has a few semantic properties for an object defined (section 2.3: who can change it, what are dependencies on other instantiations of objects, how a value changes in a domain, etc.). But in the future objects might need other properties, so flexibility is important. Beside this concept of semantic properties for an object; the concept of abstraction is essential. So there should be a way how to abstract the intricate insides of a network into something that people want to export to others. Abstracting is important if one wants to allow people to hide certain things. This is analogous to for instance the reason of the existence of BGP. Abstracting can be done outside the semantics of a description language or the Stitching Framework of course. I don't know if the above helps, but the most important attributes of the languages are for me (related to your work) are: . there are semantic related properties . and the name of object does have to be known (allowing for extendibility and non-standard situations; like research/testing). All the best, Victor -- Victor Reijs, Network Development Manager HEAnet Limited, Ireland's Education and Research Network 1st Floor, 5 George's Dock, IFSC, Dublin 1 Registered in Ireland, no 275301 tel: +353-1-660 9040 fax: +353-1-660 3666 web: http://www.heanet.ie/