Tutorial Starts 7PM

1. “Patience, learn you must” TutorialStarts7PM

2. Start recording! • Recordings in various formats will be available in a few days • Check out the Tutor Group Forums for: • Recording links • Copies of slides • Any follow questions and answers • Please use the “chat” box to chat! • Bad enough listening to me for 90 minutes • At least you can chat to the other students • Any subject you like, I will ignore box except for questions!

3. T320Tutorialtwo Protocols, XML & TMA02

4. Proposed agenda • Where are we? • Eclipse • Protocols • XML • Data • Metadata • Tools • Schema Design • TMA Tips, Q & A • Any questions, please click the “raise your hand” icon • Then type question in chat box • Or use microphone!

5. Proposed Un-agenda(?) • Security • This is well covered (for our purposes) in Block 2 Part 2 • But be aware that this is a BIG subject • You are NOT an expert just having read Part 2! • Message Transport over HTTP • Also well covered, Block 2 part 3 • But the protocol stuff here will be useful • The practical work • Thoroughly described in Block 2 parts 4-7 • Excellent support from the appropriate national forums

6. “If there's a bright center to the universe, you're on the planet that it's farthest from.” Where Are We?

7. Overview E M A pt 2 Block 1 – E-Business in context TMA01 You AreHere Block 2 – Protocols and Data TMA02 Block 3 – Web Services TMA03 Block 4 – Business Processes EMA pt 1

8. Block 2 • You need to read (and understand!) most of block 2 material before starting TMA02 • You have 2 ½ weeks remaining • Do not panic! • If really pushed for time, Block 2 Part 3 is not immediately relevant to the TMA • But you will struggle with Block 3 without it • Contact your tutor if you have any questions or problems • (More on the TMA later…)

9. “That’s no moon! That’s a space station” Eclipse

10. Eclipse Tips • Don’t Panic! • Watch the video for an overview • From the T320 website • Or on the DVD • Watch the 2nd recording in the Module-Wide tutorial room • Introduction to Eclipse, XML and XML schema (Pat and Mike) ~ 1hr 12mins

11. Eclipse Layout

12. My view of eclipse(YMMV) • For any given task, there is probably something better than Eclipse • PHP editing – PHPStorm • XML Editing – Oxygen • But for integration, flexibilty and add-ons (of all types) there is little to beat it • Especially for large teams • As a developer, do I use it by choice? • Yes, but due to Inertia! First large scale IDE I used • Gradually migrating to something less “heavy” • And less “austere” (more colourful and fun!)

13. “I am C-3PO, human-Cyborg Relations...” “Don’t need a protocol droid…” Protocols

14. Block 2 Part 1 • Good, interesting material • And quite brief! • Don’t worry too much about EDI / EDIFACT • For historical interest only • Make sure you understand: • Structured and unstructured data • What a protocol is (next slide)

15. What Is a Protocol? • 1 - The pattern of message exchange • How is an interaction started? Who can start it? • How do we take turns? Synchronous or asynchronous? • What is the procedure for handling errors? • How to manage acknowledgements? • How to end / complete the interaction • Interesting aside… • If we expect the other guy to acknowledge our message was received, should we acknowledge their acknowledgement?

16. What Is a Protocol? • 1 - The pattern of message exchange • How is an interaction started? Who can start it? • How do we take turns? Synchronous or asynchronous? • What is the procedure for handling errors? • How to manage acknowledgements? • How to end / complete the interaction • Interesting aside… • If we expect the other guy to acknowledge our message was received, should we acknowledge their acknowledgement? • Look up “The Two Generals’ Problem” on Wikipedia

17. What Is a Protocol? • 2 – The format and semantics of messages • The arrangement of data • Where stuff starts and ends • What format the data is in • The difference between “protocol data” and “payload data” • What does the data mean? • Especially the “protocol data” e.g. flags, lengths, checksums • The “payload data” mayjust be “data” (i.e. treated as a single “chunk” of bytes

18. Example ProtocolS • “Good Evening” • “Table for four please” • “This way please” • “Thank you” • “Here are your menus, would you like to order your drinks now?” • GET /t320/index.cfm HTTP/1.1 • Host: dell400.open.ac.uk • HTTP/1.1 200 OK • Server: Microsoft-IIS/4.0 • Date: Mon, 01 Jul 2002 13:38:27 GMT • Content-Length 2722

19. Layered PRotocols • Block 2 Part 3 – Message Exchange over HTTP • Important to understand “Layered Protocols”

20. “What’s in there?” “Only what you take with you…” XML

21. XML terminology • <item about=“this”>A string of Characters</item> Name Value Attribute ElementContent Start Tag End Tag Element

22. XML Data • Can be in the content… • <h1>My Webpage</h1 • Can be in an attribute value… • <imgsrc=“http://xkcd.org/1011.jpg”/> • Can be the presence of the element itself… • <hr />

23. METAData • It is a useful distinction to talk about “data” and “metadata” • “Metadata” is “data about the data” • It is NOT the data itself, but is additional information that helps interpret or categorise the data • Could also consider it “primary” vs. “secondary” data • <fuel-load units=“litres”>10000</fuel-load> • Or the MP3 “tags” that provide artist, album, & genre details

24. Creating XML • By hand, in an editor • Not typical, except authoring of structured documents • Where there is much more content than structure • E.g. Oxygen XML/Author to create product manual • Programmatically (i.e. through a computer program) • By writing out XML as a text file • Need to know ALL the data beforehand • (Except in very trivial cases, like log files) • Need to know ALL the structure beforehand • Or use a DOM Interface…

25. Creating XML through a dom interface • Remember, XML has a hierarchical (tree like) structure • So we can create that tree by adding “branches” as required, where required (and then move them around!) • A typical DOM interface has functions like: • Document.CreateElement(ElementName) • Element.AddAttribute(Name,Value) • Element.AddChild(Element) / Element.RemoveChild() • Element.AddContent(CharacterData) • When complete, write out as an XML file • Document.CreateXMLFile(RootElement)

26. XML Hierarchy

27. Reading XML - DOM • We can also use a DOM interface to read XML • Typical functions include: • Document.ReadXMLFile(Filename) • Element.GetAttribute(Name) • Element.GetContent() • Element.GetChildren() • In this way data can be read and used in a program • Points to note: • ALL the data is read in by the program • “Navigation” can be long-winded for “deep” trees

28. Reading XML – SAX • An alternative approach is to use a SAX interface • XML is read element-by-element • You tell the interface which elements you want to work on • Typical interface might be: • Create a “call back” table of elements and function calls • (i.e. call function X when you find element E) • ParseFile(Filename, CallBackTable) • How do you specify the elements you need? X-PATH

29. X-PATH • Examples: • /contact/name/familyname • //town • Others: • //Element[name=“value”] • These can get really long and complicated! (Debug tools available)

30. Converting XML • What if want to reorganise XML to match another schema? • We already know one way: • Use DOM to read in “old” XML, rearrange as required, write out “new” XML • But this requires a program to be written • Alternative is an XSLT processor • Takes an existing XML file, and a specification of changes • Creates new XML file based on: • An specification of an element pattern (X-PATH!) • Some instructions as to what to output • All these instructions are written in XML! • But can be tricky – need to understand recursion…

31. XSLT PROCESSOR Transform Specification (XML) Output XML File Input XML File XSLT Processor (application)

32. Restricting XML • With XML we can define elements and attributes at whim • It is useful to restrict XML to a specific “vocabulary” • So we can define it, share it, re-use it • Originally – Document Type Definitions ( DTD ) • Kinda weird syntax – don’t worry about this • But note that XHTML is still defined by a DTD • Newer approach XML-SCHEMA • Uses XML to define other elements, attributes • How they can be arranged • What they can contain (e.g. facets)

33. XML SCHEMAS • Best developed using a graphical tool • E.g. Eclipse • But there are better (paid for) tools • Other tools may validate XML against a schema • E.g. DOM Interface usually has option to validate • Document.ReadXMLFile(FileName,Validate=true) • If you know (and trust) the source it may not always be necessary to validate files (does take time & resources)

34. Schema Design • Karl’s Tips for Real Life Schema Design • (Not really necessary for the TMA – i.e. no extra marks!) • Always include schema version no. in your XML • Helps to maintain backwards compatibility • Use element content for data, attributes for metadata • Makes difference clearer, easier to set defaults • Look for opportunities to re-use elements & data • But be aware cannot enforce internal consistency in schema (e.g. unique IDs, cross-references etc.) • Be careful placing mandatory elements (ideally, first) • Helps with forward compatibility (new elements)

35. "You're in a desert, walking along in the sand, when all of a sudden..." "Is this the test now?" TMA02 Tips Q & A

36. TMA02 Q1 • Based on example data gathering form, develop a schema and example XML data file • You are developing a data representation NOT trying to reproduce the form • The form is provided as an example of how the data is gathered at present • Remember, we want a format in which data can be used in for automation

37. Example of use PossibleDestinations: Other programs Printouts Different XML file PossibleSources: Typed by a person Created in another program Computer Program XMLDocument Possible Actions: Use for database lookup Combine with other data Store in a database Database

38. The “right” answer? • There isn’t one! • There is a wide range of answers because: • XML can be used in various ways • Elements vs. Attributes • Element organisation / hierarchy / optionality • Element & attribute naming • Strictness vs. flexibility • Hence Q1(c) • Explain, in your terms, why you made particular choices • Any, sensible justification is fine!

39. TMA02 Q2 • (a) Tests your understanding of namespaces • Well covered in the course material • (b) Comparing various XML tools in a specific scenario • Some in course material, but also this presentation • (c) Industry Standards vs bespoke development • Standards were covered in Block 1 • Think about pros and cons • (d) Short report on using image metadata • See this presentation about “metadata” • Don’t worry about references

40. TMA02 Tips • There are no tricks or traps! • So don’t look for them… • Largely straight forward • But don’t leave it too late to start… • No word count limits • But longer is not always better! • Look at the marks breakdown • Use this to guide your time

41. Any Questions? • Please type below or in the chat box • Click on the “Raise your hand” icon to use your microphone

42. “Difficult to see, always in motion is the future” What Next?

43. Thank you for watching! • TMA02 Submission date 2nd May • Block 3 Material available 16th April • Any questions or problems email k.r.wilcox@open.ac.uk • Check the Tutor Group Forum for slides & recordings • Next tutorial: 28th May