[glue-wg] How to Work with Glue! WRT wLCG Vo Views

[Laurence Field]

Hi Owen

I am not sure what you a referring to as VO service objects, please could you explain what you mean by this in more detail. The Glue Schema just defines an abstract vocabulary for describing grid entities. Further markup of the Glue schema during deployment is envisaged and expected. There are various placeholders in existing entries for additional attributes and vendor specific extensions can always be defined. As most of the attributes are optional in Glue, it is not expected that everything will be published, only what is really needed to meet the specific use cases. To ensure interoperation between infrastructures, an interoperability profile needs to be defined which expresses what attributes are mandatory for the cross infrastructure use cases. 

I completely understand the need for VO based information and the ability to annotate the information. This is a real use case which is already in use for wLCG as you pointed out. However,this has more to do with the information system implementation rather than the schema. Essentially there are two different views of the grid, an infrastructure centric view and a VO centric view. The current version of the schema and information system does in take an infrastructure centric view. The Glue schema is a response to meet the existing demand for such a solution based on the current way of thinking. As grid infrastructures evolve and grid initiatives like EGI have more influence, we might see a paradigm shift which will require a change in Glue. However, before we started defining Glue 2.0, there were many discussions, including alignment with the OGF reference model, all of which have an infrastructure centric view. 

The problem highlighted is that VOs have there own vocabulary, naming and semantics that is important to them eg the wLCG Tier structures. However, this is specific to the VO and is something that does not need agreement. The VO is free to define there own vocabulary. The real problem is a technical one on how this information is used within an information system. For EGEE we have have evolved various mechanisms to do this, such as the FCR mechanism. 

I am really happy that you bring up the idea of Glue 3.0! As I said in my previous mail Glue 2.0 is not the end but just the being. As we are currently finalizing the specification, this is the wrong time to revisit the discussions on the fundamental model. Over time and through the influence of EGI etc, we may see a shift in the fundamental model to which this group must respond. 


Laurence