[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [Elist Home]
Subject: [relax-ng] Fw: commens on RELAX NG specification..
Forwarded by Kohsuke Kawaguchi <kohsuke.kawaguchi@sun.com> ----------------------- Original Message ----------------------- From: Murali Mani <mani@CS.UCLA.EDU> To: <kk@kohsuke.org>, <mmurata@trl.ibm.com> <dongwon@psu.edu> Date: Thu, 8 Aug 2002 09:33:11 -0700 (PDT) Subject: commens on RELAX NG specification.. ---- editorial comments: (1) Section 6.2.8, semantics titled data2 I think your second antecedent should be (not (cx |- {};s =~p) that is you should not have a The remaining two are simple typos: (2) Section 4.5 ... (at the time of writing (rather than "at the term of writing")... (3) Section 6.2.7. 1st para 3rd sentence On the other hand ... (rather than "On the hand"..) that is all the mistakes I could find trying hard to find them.. :) The spec is really good... the simplification rules and the order, I wonder how anyone could have thought through this whole process. Also, suitability of RELAX NG for data modeling... (Note: I met Kohsuke, and he mentioned other possible ways of doing this. What I mean by this is ability to infer entity types and relationship types from a relax ng grammar. Kohsuke mentioned that we can probably do annotations and use them to infer, that is very possible).. Anyways, what are entity types and relationship types? Let us consider a simple example -- students and professors. in other words we have student entities and professor entities, also every student entity is related to a professor entity by the relationship advisor.. Also let us introduce some attributes also, every student has an attribute Sname, professor has an attribute Pname, and the relationship has an attribute Since, which gives the year from which the professor was an advisor for the student. Also let us restrict that a student can have one and exactly one advisor. an example, let us consider three student entities Dongwon Lee Yun Chi Murali two professor entities Muntz Chu relationship be described as Dongwon Lee Chu 1997 Yun Chi Muntz 2000 Murali Muntz 1998 How can we represent the same in XML?? <professor> <Pname>Muntz</Pname> <student> <Sname>Murali</Sname> <Since>1998</Since> </student> <student> <Sname>Yun Chi</Sname> <Since>2000</Since> </student> </professor> <professor> <Pname>Chu</Pname> <student> <Sname>Dongwon Lee</Sname> <Since>1997</Since> </student> </professor> Now let us go back to original entities, we can describe this using ER diagram using entity types and relationship types as student ----------- ADVISOR ----------- professor (1,1) (0,n) here the cardinality means, a particular student participates once, and exactly once in the relationship... Can we do the modeling using RELAX NG. Yes -- there are two questions - (1) a profesor has two child elements -- Pname, student -- in this case Pname is an attribute of professor and student is another entity.. how do we distinguish between them.. (2) Another question is -- student has two child elements again -- Sname, Since -- Sname is an attribute of student, and Since is an attribute of the relationship.. how do we distinguish them. the answer to (1) is - consider the full syntax for relax ng, we will define names for professor and student, and we will not define a name for Pname, Sname, Since.. this is one technique utilizing the relax ng syntax to infer Entity types and relationship types. Kohsuke suggested that we can also use annotations for the same.. that is fine... The answer to (2) is -- relational schema also does not make this distinction, and no one really seems to care... of course, kohsuke's suggestion of using annotations will work even here.. I think this is long enough.. Murata-san, there was one more thing.. I think we are ready with the paper, right?? what is the next step?? do you wish to do one more teleconference, are there more things to be worked on?? thanks and regards - murali. --------------------- Original Message Ends -------------------- regards, -- Kohsuke KAWAGUCHI Sun Microsystems kohsuke.kawaguchi@sun.com
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [Elist Home]
Powered by eList eXpress LLC